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C language

questions and answers

1. What does static variable mean?
: Static variables are the variables which retain their values
between the function calls. They are initialized only once their scope is within the function in which
they are defined.
2. What is a pointer?
Ans: Pointers are variables which stores the addre
ss of
another variable. That variable may be a scalar (including another pointer), or an aggregate (array or
structure). The pointed
to object may be part of a larger object, such as a field of a structure or an
element in an array.

3. What are the uses o
f a pointer?
Ans: Pointer is used in the following cases i) It is used to access
array elements ii) It is used for dynamic memory allocation. iii) It is used in Call by reference iv) It is
used in data structures like trees, graph, linked list etc.

4. Wha
t is a structure?
Ans: Structure constitutes a super data type which represents several
different data types in a single unit. A structure can be initialized if it is static or global.

5. What is a union?
Ans: Union is a collection of heterogeneous data t
ype but it uses efficient
memory utilization technique by allocating enough memory to hold the largest member. Here a
single area of memory contains values of different types at different time. A union can never be

6. What are the differences

between structures and union?
Ans: A structure variable contains
each of the named members, and its size is large enough to hold all the members. Structure elements
are of same size. A union contains one of the named members at a given time and is large e
nough to
hold the largest member. Union element can be of different sizes.

7. What are the differences between structures and arrays?
Ans: Structure is a collection of
heterogeneous data type but array is a collection of homogeneous data types.

t is a collection of data items of same data type. 2
It has declaration only 3
.There is no
keyword. 4

array name represent the address of the starting element.

It is a collection of data items of different data type. 2

It has declaration an
d definition

keyword struct is used 4
Structure name is known as tag it is the short hand notation of the

8. In header files whether functions are declared or defined?
Ans: Functions are declared within
header file. That is function protot
ypes exist in a header file,not function bodies. They are defined in
library (lib).

9. What are the differences between malloc () and calloc ()?
Ans: Malloc Calloc 1
Malloc takes
one argument Malloc(a);where a number of bytes 2
memory allocated contains ga
rbage values 1
Calloc takes two arguments Calloc(b,c) where b no of object and c size of object 2
It initializes the
contains of block of memory to zerosMalloc takes one argument, memory allocated contains garbage
values. It allocates contiguous memory loc
ations. Calloc takes two arguments, memory allocated
contains all zeros, and the memory allocated is not contiguous.

10. What are macros? What are its advantages and disadvantages?
Ans: Macros are
abbreviations for lengthy and frequently used statements.
When a macro is called the entire code is
substituted by a single line though the macrodefinition is of several lines. The advantage of macro is
that it reduces the time taken for control transfer as in case of function.

The disadvantage of it is here the

entire code is substituted so the program becomes lengthy if a
macro is called several times.

11. Difference between pass by reference and pass by value? Ans:
Pass by reference passes a
pointer to the value. This allows the callee to modify the variable

directly.Pass by value gives a copy
of the value to the callee. This allows the callee to modify the value without modifying the variable.
(In other words, the callee simply cannot modify the variable, since it lacks a reference to it.)

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12. What is stati
c identifier? Ans:
A file
scope variable that is declared static is visible only to
functions within that file. A function
scope or block
scope variable that is declared as static is visible
only within that scope. Furthermore, static variables only have a

single instance. In the case of

or block
scope variables, this means that the variable is not “automatic” and thus retains its
value across function invocations.

13. Where is the auto variables stored? Ans:
Auto variables can be stored anywhere
, so long as
recursion works. Practically, they‟re stored on the stack. It is not necessary that always a stack exist.
You could theoretically allocate function invocation records from the heap.

14. Where does global, static, and local, register variables
, free memory and C Program
instructions get stored? Ans:
Global: Wherever the linker puts them. Typically the “BSS segment”
on many platforms. Static: Again, wherever the linker puts them. Often, they‟re intermixed with the
globals. The only difference be
tween globals and statics is whether the linker will resolve the
symbols across compilation units.Local: Typically on the stack, unless the variable gets register
allocated and never spills.Register: Nowadays, these are equivalent to “Local” variables. The
y live
on the stack unless they get register

15. Difference between arrays and linked list? Ans:
An array is a repeated pattern of variables in
contiguous storage. A linked list is a set of structures scattered through memory, held together by
pointers in each element that point to the next element. With an array, we can (on most architectures)
move from one element to the next by adding a fixed constant to the integer value of the pointer.
With a linked list, there is a “next” pointer in each s
tructure which says what element comes next.

16. What are enumerations? Ans:
They are a list of named integer
valued constants.

color { black , orange=4, yellow, green, blue, violet };This declaration defines the
symbols “black”, “orange”, “yellow”, etc. to have the values “1,” “4,” “5,” … etc. The difference
between an enumeration and a macro is that the enum actually declares a
type, and therefore can be
type checked.

17. Describe about storage allocation and scope of global, extern, static, local and register

Globals have application
scope. They‟re available in any compilation unit that includes an
appropriate declar
ation (usually brought from a header file). They‟re stored wherever the linker puts
them, usually a place called the “BSS segment.” Extern? This is essentially “global.”
the same place as globals, typically, but only available to the compila
tion unit that contains them. If
they are block
scope global, only available within that block and its subblocks.
Stored on the
stack, typically. Only available in that block and its subblocks. (Although pointers to locals can be
passed to functions

invoked from within a scope where that local is valid.)
See tirade
above on “local” vs. “register.” The only difference is that the C compiler will not let you take the
address of something you‟ve declared as “register.”

18. What are register v
ariables? What are the advantages of using register variables? Ans:
If a
variable is declared with a register storage class,it is known as register variable.The register variable
is stored in the cpu register instead of main memory.Frequently used variable
s are declared as
register variable as it‟s access time is faster.

19. What is the use of typedef? Ans:
The typedef help in easier modification when the programs are
ported to another machine. A descriptive new name given to the existing data type may be
easier to
understand the code.

20. Can we specify variable field width in a scanf() format string? If possible how? Ans
: All
field widths are variable with scanf(). You can specify a maximum field width for a given field by
placing an integer value betwee
n the „%‟ and the field type specifier. (e.g. %64s). Such a specifier
will still accept a narrower field width. The one exception is %#c (where # is an integer). This reads
EXACTLY # characters, and it is the only way to specify a fixed field width with sc

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21. Out of fgets() and gets() which function is safe to use and why? Ans:
fgets() is safer than
gets(), because we can specify a maximum input length. Neither one is completely safe, because the
compiler can’t prove that programmer won’t overflow t
he buffer he pass to fgets ().
22. Difference
between strdup and strcpy? Ans:
Both copy a string. strcpy wants a buffer to copy into. strdup
allocates a buffer using malloc(). Unlike strcpy(), strdup() is not specified by ANSI .

23. What is recursion? Ans
A recursion function is one which calls itself either directly or
indirectly it must halt at a definite point to avoid infinite recursion.

24. Differentiate between for loop and a while loop? What are it uses? Ans:
For executing a set
of statements fixe
d number of times we use for loop while when the number of iterations to be
performed is not known in advance we use while loop.

25. What is storage class? What are the different storage classes in C? Ans:
Storage class is an
attribute that changes the be
havior of a variable. It controls the lifetime, scope and linkage. The
storage classes in c are auto, register, and extern, static, typedef.

26. What the advantages of using Unions? Ans:
When the C compiler is allocating memory for
unions it will always r
eserve enough room for the largest member.

27. What is the difference between Strings and Arrays? Ans:
String is a sequence of characters
ending with NULL .it can be treated as a one dimensional array of characters terminated by a NULL

28. Wha
t is a far pointer? Where we use it? Ans:
In large data model (compact, large, huge) the
address B0008000 is acceptable because in these model all pointers to data are 32bits long. If we use
small data model(tiny, small, medium) the above address won’t wor
k since in these model each
pointer is 16bits long. If we are working in a small data model and want to access the address
B0008000 then we use far pointer. Far pointer is always treated as a 32bit pointer and contains a
segment address and offset address
both of 16bits each. Thus the address is represented using
segment : offset format B000h:8000h. For any given memory address there are many possible far
address segment : offset pair. The segment register contains the address where the segment begins
and o
ffset register contains the offset of data/code from where segment begins.

29. What is a huge pointer? Ans:
Huge pointer is 32bit long containing segment address and offset
address. Huge pointers are normalized pointers so for any given memory address ther
e is only one
possible huge address segment: offset pair. Huge pointer arithmetic is doe with calls to special
subroutines so its arithmetic slower than any other pointers.

30. What is a normalized pointer, how do we normalize a pointer? Ans:
It is a 32bi
t pointer,
which has as much of its value in the segment register as possible. Since a segment can start every
16bytes so the offset will have a value from 0 to F. for normalization convert the address into 20bit
address then use the 16bit for segment addr
ess and 4bit for the offset address. Given a pointer 500D:
9407,we convert it to a 20bitabsolute address 549D7,Which then normalized to 549D:0007.

31. What is near pointer? Ans:
A near pointer is 16 bits long. It uses the current content of the CS
(code s
egment) register (if the pointer is pointing to code) or current contents of DS (data segment)
register (if the pointer is pointing to data) for the segment part, the offset part is stored in a 16 bit
near pointer. Using near pointer limits the data/code t
o 64kb segment.
32. In C, why is the void
pointer useful? When would you use it? Ans:
The void pointer is useful because it is a generic
pointer that any pointer can be cast into and back again without loss of information.

33. What is a NULL Pointer? Whether it is same as an uninitialized pointer? Ans:
Null pointer
is a pointer which points to nothing but uninitialized pointer may point to anywhere.

34. Are pointers integer? Ans:
No, pointers are not integers. A pointer is
an address. It is a positive

35. What does the error ‘Null Pointer Assignment’ means and what causes this error? Ans:
null pointer points to nothing so accessing a uninitialized pointer or invalid location may cause an

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36. What is gener
ic pointer in C? Ans:
In C void* acts as a generic pointer. When other pointer
types are assigned to generic pointer, conversions are applied automatically (implicit conversion).

37. Are the expressions arr and &arr same for an array of integers? Ans:

for array of
integers they are same.

38. IMP>How pointer variables are initialized? Ans:
Pointer variables are initialized by one of the
following ways. I. Static memory allocation II. Dynamic memory allocation

39. What is static memory allocation? Ans:

Compiler allocates memory space for a declared
variable. By using the address of operator, the reserved address is obtained and this address is
assigned to a pointer variable. This way of assigning pointer value to a pointer variable at
compilation time i
s known as static memory allocation.

40. What is dynamic memory allocation? Ans:
A dynamic memory allocation uses functions such
as malloc() or calloc() to get memory dynamically. If these functions are used to get memory
dynamically and the values returne
d by these function are assigned to pointer variables, such a way
of allocating memory at run time is known as dynamic memory allocation.

41. What is the purpose of realloc? Ans:
It increases or decreases the size of dynamically allocated
array. The funct
ion realloc (ptr,n) uses two arguments. The first argument ptr is a pointer to a block
of memory for which the size is to be altered. The second argument specifies the new size. The size
may be increased or decreased. If sufficient space is not available t
o the old region the function may
create a new region.
42. What is pointer to a pointer? Ans:
If a pointer variable points another
pointer value. Such a situation is known as a pointer to a pointer. Example: int *p1,**p2,v=10;
P1=&v; p2=&p1; Here p2 is a p
ointer to a pointer.

43. What is an array of pointers? Ans:
if the elements of an array are addresses, such an array is
called an array of pointers.

44. Difference between linker and linkage? Ans:
Linker converts an object code into an executable
code by

linking together the necessary built in functions. The form and place of declaration where the
variable is declared in a program determine the linkage of variable.

45. Is it possible to have negative index in an array? Ans:
Yes it is possible to index wi
th negative
value provided there are data stored in this location. Even if it is illegal to refer to the elements that
are out of array bounds, the compiler will not produce error because C has no check on the bounds of
an array.

46. Why is it necessary t
o give the size of an array in an array declaration? Ans:
When an array
is declared, the compiler allocates a base address and reserves enough space in memory for all the
elements of the array. The size is required to allocate the required space and hence
size must be

47. What modular programming? Ans:
If a program is large, it is subdivided into a number of
smaller programs that are called modules or subprograms. If a complex problem is solved using more
modules, this approach is known as modul
ar programming.

48. What is a function? Ans:
A large program is subdivided into a number of smaller programs or
subprograms. Each subprogram specifies one or more actions to be performed for the larger program.
Such sub programs are called functions.

What is an argument? Ans:
An argument is an entity used to pass data from the calling to a
called function.

50. What are built in functions? Ans:
The functions that are predefined and supplied along with the
compiler are known as built
in functions. They
are also known as library functions.

51. Difference between formal argument and actual argument? Ans:
Formal arguments are the
arguments available in the function definition. They are preceded by their own data type. Actual
arguments are available in the function call. These arguments are given as constants or variables or
expressions to pass the values to

the function.

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52. Is it possible to have more than one main() function in a C program ? Ans:
The function
main() can appear only once. The program execution starts from main.

53. What is the difference between an enumeration and a set of pre
processor # defines? Ans:
There is hardly any difference between the two, except that #defines has a global effect (throughout
the file) whereas an enumeration can have an effect local to t
he block if desired. Some advantages of
enumeration are that the numeric values are automatically assigned whereas in #define we have to
explicitly define them. A disadvantage is that we have no control over the size of enumeration

54. How are
Structure passing and returning implemented by the complier? Ans:
structures are passed as argument to functions, the entire structure is typically pushed on the stack.
To avoid this overhead many programmer often prefer to pass pointers to structure
instead of actual
structures. Structures are often returned from functions in a location pointed to by an extra, compiler
supported „hidden‟ argument to the function.

55. IMP>what is the similarity between a Structure, Union and enumeration? Ans:
All of t
let the programmer to define new data type.

56. Can a Structure contain a Pointer to itself? Ans:
Yes such structures are called self

57. How can we read/write Structures from/to data files? Ans:
To write out a structure we ca
use fwrite() as Fwrite( &e, sizeof(e),1,fp);Where e is a structure variable. A corresponding fread()
invocation can read the structure back from file. calling fwrite() it writes out sizeof(e) bytes from the
address &e. Data files written as memory images

with fwrite(),however ,will not be portable,
particularly if they contain floating point fields or Pointers. This is because memory layout of
structures is machine and compiler dependent. Therefore, structures written as memory images
cannot necessarily b
e read back by programs running on other machine, and this is the important
concern if the data files you‟re writing will ever be interchanged between machines.

58. Write a program which employs Recursion? Ans:
int fact(int n) { return n > 1 ? n * fact(n

: 1; }

59.Write a program which uses Command Line Arguments? Ans:

#include void main(int argc,char *argv[]) { int i; clrscr(); for(i=0;i printf(“
n%d”,argv[i]); }

60. Difference between array and pointer? Ans: Array

Array allocates space automati
cally 2

cannot be resized 3

It cannot be reassigned 4

sizeof (arrayname) gives the number of bytes
occupied by the array.
Explicitly assigned to point to an allocated space. 2
It can be sized
using realloc() 3
pointer can be reassigned. 4
izeof (p) returns the number of bytes used to store the
pointer variable p.

61. What do the ‘c’ and ‘v’ in argc and argv stand for? Ans:
The c in argc(argument count)
stands for the number of command line argument the program is invoked with and v in
(argument vector) is a pointer to an array of character string that contain the arguments.
IMP>what are C tokens? Ans:
There are six classes of tokens: identifier, keywords, constants,
string literals, operators and other separators.

63. What are C id
entifiers? Ans:
These are names given to various programming element such as
variables, function, arrays.It is a combination of letter, digit and underscore.It should begin with
letter. Backspace is not allowed.

64. Difference between syntax vs logical er
ror? Ans: Syntax Error
These involves validation of
syntax of language. 2
compiler prints diagnostic message.

Logical Error
logical error are caused by an incorrect algorithm or by a statement mistyped in
such a way that it doesn’t violet syntax of la
nguage. 2
difficult to find.

65. What is preincrement and post increment? Ans:
++n (pre increment) increments n before its
value is used in an assignment operation or any expression containing it. n++ (post increment) does
increment after the value of n i
s used.

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66. Write a program to interchange 2 variables without using the third one. Ans:
a ^= b; ie
a=a^b b ^= a; ie b=b^a; a ^= b ie a=a^b; here the numbers are converted into binary and then xor
operation is performed. You know, you’re just asking “have

you seen this overly clever trick that’s
not worth applying on modern architectures and only really applies to integer variables?”

67. What is the maximum combined length of command line arguments including the space
between adjacent arguments? Ans:
It d
epends on the operating system.

68. What are bit fields? What is the use of bit fields in a Structure declaration? Ans:
A bit field
is a set of adjacent bits within a single implementation based storage unit that we will call a “word”.
The syntax of field
definition and access is based on structure. Struct { unsigned int k :1; unsigned int
l :1; unsigned int m :1; }flags; the number following the colon represents the field width in bits.Flag
is a variable that contains three bit fields.

69. What is a prepr
ocessor, what are the advantages of preprocessor? Ans:
A preprocessor
processes the source code program before it passes through the compiler. 1

a preprocessor involves
the readability of program 2

It facilitates easier modification 3

It helps in writin
g portable programs

It enables easier debugging 5

It enables testing a part of program 6

It helps in developing
generalized program

70. What are the facilities provided by preprocessor? Ans:
file inclusion 2
substitution facility
conditional comp

71. What are the two forms of #include directive? Ans:
1.#include”filename” 2.#include the first
form is used to search the directory that contains the source file.If the search fails in the home
directory it searches the implementation defined l
ocations.In the second form ,the preprocessor
searches the file only in the implementation defined locations.

72. How would you use the functions randomize() and random()? Ans:
Randomize() initiates
random number generation with a random value. Random() g
enerates random number between 0 and
73. What do the functions atoi(), itoa() and gcvt() do? Ans:
atoi() is a macro that converts
integer to character. itoa() It converts an integer to string gcvt() It converts a floating point number to
74. How would you use the functions fseek(), freed(), fwrite() and ftell()? Ans:
fseek(f,1,i) Move the pointer for file f a distance 1 byte from location i. fread(s,i1,i2,f) Enter i2
dataitems,each of size i1 bytes,from file f to string s. fwrite(s,i1,i2,f
) send i2 data items,each of size
i1 bytes from string s to file f. ftell(f) Return the current pointer position within file f.

The data type returned for functions fread,fseek and fwrite is int and ftell is long int.

75. What is the difference between t
he functions memmove() and memcpy()? Ans:
arguments of memmove() can overlap in memory. The arguments of memcpy() cannot.

76. What is a file? Ans:
A file is a region of storage in hard disks or in auxiliary storage devices.It
contains bytes of informa
tion .It is not a data type.

77. IMP>what are the types of file? Ans:
Files are of two types 1
high level files (stream oriented
files) :These files are accessed using library functions 2
low level files(system oriented files) :These
files are accessed us
ing system calls

78. IMP>what is a stream? Ans:
A stream is a source of data or destination of data that may be
associated with a disk or other I/O device. The source stream provides data to a program and it is
known as input stream. The destination strea
m eceives the output from the program and is known as
output stream.

79. What is meant by file opening? Ans:
The action of connecting a program to a file is called
opening of a file. This requires creating an I/O stream before reading or writing the data.

80. What is FILE? Ans:
FILE is a predefined data type. It is defined in stdio.h file.

81. What is a file po
inter? Ans:
The pointer to a FILE data type is called as a stream pointer or a
file pointer. A file pointer points to the block of information of the stream that had just been opened.
82. How is fopen()used ? Ans:
The function fopen() returns a file pointe
r. Hence a file pointer is
declared and it is assigned as FILE *fp; fp= fopen(filename,mode); filename is a string representing
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the name of the file and the mode represents: “r” for read operation “w” for write operation “a” for
append operation “r+”,”w+”,
”a+” for update operation

83How is a file closed ? Ans:
A file is closed using fclose() function Eg. fclose(fp); Where fp is a
file pointer.

84. What is a random access file? Ans:
A file can be accessed at random using fseek() function
origin); fp file pointer position number of bytes offset from origin origin 0,1 or 2
denote the beginning ,current position or end of file respectively.

85. What is the purpose of ftell ? Ans:
The function ftell() is used to get the current file represent
by the file pointer. ftell(fp); returns a long integer value representing the current file position of the
file pointed by the file pointer fp.If an error occurs ,
1 is returned.

86. What is the purpose of rewind() ? Ans:
The function rewind is used to

bring the file pointer to
the beginning of the file. Rewind(fp); Where fp is a file pointer.Also we can get the same effect by

87. Difference between a array name and a pointer variable? Ans:
A pointer variable is a
variable where as an arr
ay name is a fixed address and is not a variable. A pointer variable must be
initialized but an array name cannot be initialized. An array name being a constant value , ++ and

operators cannot be applied to it.

88. Represent a two
dimensional array using

pointer? Ans:
Address of a[I][j] Value of a[I][j] &a[I][j] or a[I] + j or *(a+I) + j *&a[I][j] or a[I][j] or *(a[I] + j ) or
*( * ( a+I) +j )

89. Difference between an array of pointers and a pointer to an array? Ans: Array of pointers

Declaration is:

data_type *array_name[size]; 2
Size represents the row size. 3

The space for
columns may be dynamically

Pointers to an array
Declaration is data_type ( *array_name)[size]; 2
Size represents the column

90. Can we use any name in place of argv an
d argc as command line arguments ? Ans:
yes we
can use any user defined name in place of argc and argv;

91. What are the pointer declarations used in C? Ans:

Array of pointers, e.g , int *a[10]; Array
of pointers to integer 2
Pointers to an array,e.g
, int (*a)[10]; Pointer to an array of into 3
returning a pointer,e.g, float *f( ) ; Function returning a pointer to float 4
Pointer to a pointer ,e.g, int
**x; Pointer to apointer to int 5
pointer to a data type ,e.g, char *p; pointer to char

between a constant pointer and pointer to a constant? Ans:
const char *p; //pointer to a const
character. char const *p; //pointer to a const character. char * const p; //const pointer to a char
variable. const char * const p; // const point
er to a const character.

93. Is the allocated space within a function automatically deallocated when the function
returns? Ans:
No pointer is different from what it points to .Local variables including local pointers
variables in a function are deallocate
d automatically when function returns.,But in case of a local
pointer variable ,deallocation means that the pointer is deallocated and not the block of memory
allocated to it. Memory dynamically allocated always persists until the allocation is freed or th
program terminates.

94. Discuss on pointer arithmetic? Ans:

Assignment of pointers to the same type of pointers. 2

Adding or subtracting a pointer and an integer. 3
subtracting or comparing two pointer. 4
incrementing or decrementing the pointers po
inting to the elements of an array. When a pointer to an
integer is incremented by one , the address is incremented by two. It is done automatically by the
compiler. 5
Assigning the value 0 to the pointer variable and comparing 0 with the pointer. The
ter having address 0 points to nowhere at all.

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95. What is the invalid pointer arithmetic? Ans:
i) adding ,multiplying and dividing two pointers.
ii) Shifting or masking pointer. iii) Addition of float or double to pointer. iv) Assignment of a pointer
one type to a pointer of another type ?

96. What are the advantages of using array of pointers to string instead of an array of strings?

i) Efficient use of memory. ii) Easier to exchange the strings by moving their pointers while

97. Are
the expressions *ptr ++ and ++ *ptr same? Ans:
No,*ptr ++ increments pointer and not
the value pointed by it. Whereas ++ *ptr increments the value being pointed to by ptr.

98. What would be the equivalent pointer expression foe referring the same element
a[p][q][r][s] ? Ans :
*( * ( * ( * (a+p) + q ) + r ) + s)

99. Are the variables argc and argv are always local to main? Ans:
Yes they are local to main.

100. Can main () be called recursively? Ans:
Yes any function including main () can be called

101. IMP>Can we initialize unions? Ans:
ANSI Standard C allows an initializer for the first
member of a union. There is no standard way of initializing any other member (nor, under a pre
ANSI compiler, is there generally any way of initializing a

union at all).
102. What’s the difference
between these two declarations? Ans:
struct x1 { … }; typedef struct { … } x2; The first form
declares a structure tag; the second declares a typedef. The main difference is that the second
declaration is of a sli
ghtly more abstract type.its users don’t necessarily know that it is a structure,
and the keyword struct is not used when declaring instances of it.

103. Why doesn’t this code: a[i] = i++; work? Ans:
The subexpression i++ causes a side effect.it
i’s value.which leads to undefined behavior since i is also referenced elsewhere in the same

104.WHy doesn’t struct x { … }; x thestruct; work? Ans:
C is not C++. Typedef names are not
automatically generated for structure tags.

105. Why can’
t we compare structures? Ans:
There is no single, good way for a compiler to
implement structure comparison which is consistent with C’s low
level flavor. A simple byte
comparison could founder on random bits present in unused “holes” in the struct
ure (such padding is
used to keep the alignment of later fields correct). A field
field comparison might require
unacceptable amounts of repetitive code for large structures.

106. How are structure passing and returning implemented? Ans:
When structures are passed as
arguments to functions, the entire structure is typically pushed on the stack, using as many words as
are required. Some compilers merely pass a pointer to the structure, though they may have to make a
local copy to preserve p
value semantics. Structures are often returned from functions in a
location pointed to by an extra,compiler
supplied “hidden” argument to the function. Some older
compilers used a special,static location for structure returns, although this made str
functions non
reentrant, which ANSI C disallows.




questions and answers

1. What is a class? Ans:
The objects with the same data structure (attributes) and
(operations) are called class.

2. What is an object? Ans:
It is an entity which may correspond to real
world entities such as
students, employees, bank account. It may be concrete such as file system or conceptual such as
scheduling policies in m
ultiprocessor operating system. Every object will have data structures called
attributes and behavior called operations.

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3. What is the difference between an object and a class? Ans:
All objects possessing similar
properties are grouped into class.
Example :

person is a class, ram, hari are objects of person class.
All have similar attributes like name, age, sex and similar operations like speak, walk.

Class person { private: char name[20]; int age; char sex; public: speak(); walk(); };

4. What is

the difference between class and structure? Ans:
In class the data members by default
are private but in structure they are by default public

5. Define object based programming language? Ans:
Object based programming language support
encapsulation and ob
ject identity without supporting some important features of OOPs language.
Object based language=Encapsulation + object Identity

6. Define object oriented language? Ans:
oriented language incorporates all the features of
object based programming la
nguages along with inheritance and polymorphism.

c++, java.

7. Define OOPs? Ans:
OOP is a method of implementation in which programs are organized as co
operative collection of objects, each of which represents an instance of some class and whose cl
are all member of a hierarchy of classes united through the property of inheritance.

8. What is public, protected, and private? Ans:
These are access specifier or a visibility lebels
.The class member that has been declared as private can be accessed

only from within the class.
Public members can be accessed from outside the class also. Within the class or from the object of a
class protected access limit is same as that of private but it plays a prominent role in case

9. What is a scop
e resolution operator? Ans:
The scope resolution operator permits a program to
reference an identifier in the global scope that has been hidden by another identifier with the same
name in the local scope.

10. What do you mean by inheritance? Ans:
The mech
anism of deriving a new class (derived)
from an old class (base class) is called inheritance. It allows the extension and reuse of existing code
without having to rewrite the code from scratch.

11. What is abstraction? Ans:
The technique of creating user
defined data types, having the
properties of built
in data types and a set of permitted operators that are well suited to the application
to be programmed is known as data abstraction. Class is a construct for abstract data types (ADT).

12. What is encaps
ulation? Ans:
It is the mechanism that wraps the data and function it manipulates
into single unit and keeps it safe from external interference.

13. How variable declaration in c++ differs that in c? Ans:
C requires all the variables to be
declared at the

beginning of a scope but in c++ we can declare variables anywhere in the scope. This
makes the programmer easier to understand becoz the variables r declared in the context of their use.

14. What are the c++ tokens? Ans:
c++ has the following tokens I. k
eywords II. Identifiers III.
Constants IV. Strings V. operators

15. What do you mean by reference variable in c++? Ans:
A reference variable provides an alias
to a previously defined variable. Data type & reference
name = variable name

16. What do you me
an by implicit conversion? Ans:
Whenever data types are mixed in an
expression then c++ performs the conversion automatically. Here smaller type is converted to wider
type. Example

in case of integer and float integer is converted into float type.

17. Wh
at is the difference between method overloading and method overriding? Ans:
Overloading a method (or function) in C++ is the ability for functions of the same name to be defined
as long as these methods have different signatures (different set of parameter
s). Method overriding is
the ability of the inherited class rewriting the virtual method of the base class.

18. What are the defining traits of an object
oriented language?
The defining traits of an object
oriented language are: encapsulation inheritance

is a feature of OOPL that at run time depending upon the type of object the
appropriate method is called.

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is a feature of OOPL that represents the “is a” relationship between different objects
(classes). Say in real life a manager is a employee. So in OOPL manger class is inherited from the
employee class.

is a feature of OOPL that is used to h
ide the information.

19. What is polymorphism? Ans:
Polymorphism is the idea that a base class can be inherited by
several classes. A base class pointer can point to its child class and a base class array can store
different child class objects.

20. What
do you mean by inline function? Ans:
An inline function is a function that is expanded
inline when invoked.ie. the compiler replaces the function call with the corresponding function code.
An inline function is a function that is expanded in line when it i
s invoked. That is the compiler
replaces the function call with the corresponding function code (similar to macro).

21 What is the difference between a NULL pointer and a void pointer? Ans:
A NULL pointer is
a pointer of any type whose value is zero. A void pointer is a pointer to an object of an unknown
type, and is guaranteed to have enough bits to hold a pointer to any object. A void pointer is not
guaranteed to have enough bits to point t
o a function (though in general practice it does).

22. What is difference between C++ and Java? Ans:
C++ has pointers Java does not. Java is
platform independent C++ is not. Java has garbage collection C++ does not.

23. What do you mean by multiple inher
itance in C++ ? Ans:
Multiple inheritance is a feature in
C++ by which one class can be of different types. Say class teaching Assistant is inherited from two
classes say teacher and Student.

24. What do you mean by virtual methods? Ans:
virtual methods a
re used to use the
polymorphism feature in C++. Say class A is inherited from class B. If we declare say function f() as
virtual in class B and override the same function in class A then at runtime appropriate method of the
class will be called depending u
pon the type of the object.

25. What do you mean by static methods? Ans:
By using the static method there is no need
creating an object of that class to use that method. We can directly call that method on that class. For
example, say class A has static f
unction f(), then we can call f() function as A.f(). There is no need of
creating an object of class A.

26. How many ways are there to initialize an int with a constant? Ans:
Two. There are two
formats for initializers in C++ as shown in the example that
follows. The first format uses the
traditional C notation. The second format uses constructor notation. int foo = 123; int bar (123);

27. What is a constructor? Ans:
Constructor is a special member function of a class, which is
invoked automatically whene
ver an instance of the class is created. It has the same name as its class.
28. What is destructor? Ans:
Destructor is a special member function of a class, which is invoked
automatically whenever an object goes out of the scope. It has the same name as it
s class with a tilde
character prefixed.

29. What is an explicit constructor? Ans:
A conversion constructor declared with the explicit
keyword. The compiler does not use an explicit constructor to implement an implied conversion of
types. It’s purpose is r
eserved explicitly for construction.
30 What is the Standard Template
Library? Ans:
A library of container templates approved by the ANSI committee for inclusion in
the standard C++ specification. A programmer who then launches into a discussion of the gen
programming model, iterators, allocators, algorithms, and such, has a higher than average
understanding of the new technology that STL brings to C++ programming.

31. What problem does the namespace feature solve? Ans:
Multiple providers of libraries
use common global identifiers causing a name collision when an application tries to link with two or
more such libraries. The namespace feature surrounds a library’s external declarations with a unique
namespace that eliminates the potential for thos
e collisions. This solution assumes that two library
vendors don’t use the same namespace identifier, of course.

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32. What is the use of ‘using’ declaration? Ans:
A using declaration makes it possible to use a
name from a namespace

33. What is a template?

Templates allow us to create generic functions that admit any data
type as parameters and return a value without having to overload the function with all the possible
data types. Until certain point they fulfill the functionality of a macro. Its prot
otype is any of the two
following ones: template function_declaration; template function_declaration;

34. Differentiate between a template class and class template? Ans: Template class:
A generic
definition or a parameterized class not instantiated until
the client provides the needed information.
It’s jargon for plain templates.
Class template:
A class template specifies how individual classes can
be constructed much like the way a class specifies how individual objects can be constructed. It’s
jargon for

plain classes.

35. What is the difference between a copy constructor and an overloaded assignment operator?
A copy constructor constructs a new object by using the content of the argument object. An
overloaded assignment operator assigns the content
s of an existing object to another existing object
of the same class.

36. What is a virtual destructor? Ans:
The simple answer is that a virtual destructor is one that is
declared with the virtual attribute.

37. What is an incomplete type? Ans:
e type refers to pointers in which there is non
availability of the implementation of the referenced location or it points to some location whose
value is not available for modification.
int *i=0×400 // i points to address 400

*i=0; //set the valu
e of memory location pointed by i. Incomplete types are otherwise called
uninitialized pointers.

38. What do you mean by Stack unwinding? Ans:
It is a process during exception handling when
the destructor is called for all local objects between the place where the exception was thrown and
where it is caught.

39. What is a container class? What are the types of container classes? Ans:
A container

class is
a class that is used to hold objects in memory or external storage. A container class acts as a generic
holder. A container class has a predefined behavior and a well
known interface. A container class is a
supporting class whose purpose is to hi
de the topology used for maintaining the list of objects in
memory. When a container class contains a group of mixed objects, the container is called a
heterogeneous container; when the container is holding a group of objects that are all the same, the
tainer is called a homogeneous container

40. Name some pure object oriented languages? Ans:
Smalltalk, Java, Eiffel, Sather.

41. Name the operators that cannot be overloaded? Ans:
sizeof, ., .*, .
>, ::, ?:

42. What is an adaptor class or Wrapper class
? Ans:
A class that has no functionality of its own.
Its member functions hide the use of a third party software component or an object with the non
compatible interface or a non
oriented implementation.

43. What is a Null object? Ans:
It is an object of some class whose purpose is to indicate that a real
object of that class does not exist. One common use for a null object is a return value from a member
function that is supposed to return an object with some specified properties but ca
nnot find such an

44. What is class invariant? Ans:
A class invariant is a condition that defines all valid states for an
object. It is a logical condition to ensure the correct working of a class. Class invariants must hold
when an object is crea
ted, and they must be preserved under all operations of the class. In particular
all class invariants are both preconditions and post
conditions for all operations or member functions
of the class.

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45. What is a dangling pointer? Ans:
A dangling pointer a
rises when you use the address of an
object after its lifetime is over. This may occur in situations like returning addresses of the automatic
variables from a function or using the address of the memory block after it is freed.

46. Differentiate between
the message and method? Ans: Message:
Objects communicate by
sending messages to each other. A message is sent to invoke a method.
Provides response to
a message and it is an implementation of an operation

47. How can we access protected and privat
e members of a class? Ans:
In the case of members
protected and private, these could not be accessed from outside the same class at which they are
declared. This rule can be transgressed with the use of the friend keyword in a class, so we can allow
an ext
ernal function to gain access to the protected and private members of a class.

48. Can you handle exception in C++? Ans:
Yes we can handle exception in C++ using keyword:
try, catch and throw. Program statements that we want to monitor for exceptions are
contained in a
try block. If an exception occurs within the try block, it is thrown (using throw).The exception is
caught, using catch, and processed.

49. What is virtual function? Ans:
A virtual function is a member function that is declared within a
e class and redefined by a derived class .To create a virtual function, the function declaration in
the base class is preceded by the keyword virtual.

50. What do you mean by early binding? Ans:
Early binding refers to the events that occur at
compile time
. Early binding occurs when all information needed to call a function is known at
compile time. Examples of early binding include normal function calls, overloaded function calls,
and overloaded operators. The advantage of early binding is efficiency.


What do you mean by late binding? Ans:
Late binding refers to function calls that are not
resolved until run time. Virtual functions are used to achieve late binding. When access is via a base
pointer orreference, the virtual function actually called is d
etermined by the type of object pointed to
by the pointer.



questions and answers

1. What is data structure? Ans:
The logical and mathematical model of a particular organization of
data is calleddata structure. There are two types of data structure i) Linear ii) Nonlinear

2. What are the goals of Data Structure? Ans:
It must rich enough in structure to reflect the ac
relationship of data in real world. The structure should be simple enough for efficient processing of data.

3. What does abstract Data Type Mean? Ans:
Data type is a collection of values and a set of operations
on these values. Abstract data type ref
er to the mathematical concept that define the data type. It is a
useful tool for specifying the logical properties of a data type. ADT consists of two parts 1) Values
definition 2) Operation definition
The value definition for the ADT RATIONAL st
ates that
RATIONAL value consists of two integers, second doesn’t equal to zero. The operator definition for
ADT RATIONAL includes the operation of creation (make rational) addition, multiplication and test for

4. What is the difference between
a Stack and an Array? Ans:
i) Stack is a ordered collection of items
ii) Stack is a dynamic object whose size is constantly changing as items are pushed and popped . iii) Stack
may contain different data types iv) Stack is declared as a structure containin
g an array to hold the
element of the stack, and an integer to indicate the current stack top within the array. ARRAY i) Array is
an ordered collection of items ii) Array is a static object i.e. no of item is fixed and is assigned by the
declaration of the

array iii) It contains same data types. iv) Array can be home of a stack i.e. array can be
declared large enough for maximum size of the stack.

5. What do you mean by recursive definition? Ans:
The definition which defines an object in terms of
simpler c
ases of itself is called recursive definition.

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6. What is sequential search? Ans:
In sequential search each item in the array is compared with the item
being searched until a match occurs. It is applicable to a table organized either as an array or as a l

7. What actions are performed when a function is called? Ans:
When a function is called i) arguments
are passed ii) local variables are allocated and initialized ii) transferring control to the function

8. What actions are performed when a fu
nction returns? Ans:
i) Return address is retrieved ii)
Function’s data area is freed iii) Branch is taken to the return address

9. What is a linked list? Ans:
A linked list is a linear collection of data elements, called nodes, where the
linear order is
given by pointers. Each node has two parts first part contain the information of the element
second part contains the address of the next node in the list.

10. What are the advantages of linked list over array (static data structure)? Ans:
The disadvantag
of array are i) unlike linked list it is expensive to insert and delete elements in the array ii) One can’t
double or triple the size of array as it occupies block of memory space.

In linked list i) each element in list contains a field, called a link
or pointer which contains the address of
the next element ii) Successive element’s need not occupy adjacent space in memory.

11. Can we apply binary search algorithm to a sorted linked list, why? Ans:
No we cannot apply
binary search algorithm to a sorted

linked list, since there is no way of indexing the middle element in the
list. This is the drawback in using linked list as a data structure.

12. What do you mean by free pool? Ans:
Pool is a list consisting of unused memory cells which has its
own point

13. What do you mean by garbage collection? Ans:
It is a technique in which the operating system
periodically collects all the deleted space onto the free storage list. It takes place when there is minimum
amount of space left in storage list or when CPU is ideal. The alternate method to this is to immed
reinsert the space into free storage list which is time consuming.

14. What do you mean by overflow and underflow? Ans:
When new data is to be inserted into the data
structure but there is no available space i.e. free storage list is empty this sit
uation is called overflow.
When we want to delete data from a data structure that is empty this situation is called underflow.

15. What are the disadvantages array implementations of linked list? Ans:
i) The no of nodes needed
can’t be predicted when the
program is written. ii) The no of nodes declared must remain allocated
throughout its execution

16. What is a queue? Ans:
A queue is an ordered collection of items from which items may be deleted at
one end (front end) and items inserted at the other end
(rear end). It obeys FIFO rule there is no limit to
the number of elements a queue contains.

17. What is a priority queue? Ans:
The priority queue is a data structure in which the intrinsic ordering
of the elements (numeric or alphabetic) Determines the r
esult of its basic operation. It is of two types i)
Ascending priority queue

Here smallest item can be removed (insertion is arbitrary) ii) Descending
priority queue

Here largest item can be removed (insertion is arbitrary)

18. What are the disadvantage
s of sequential storage? Ans:
i) Fixed amount of storage remains
allocated to the data structure even if it contains less element. ii) No more than fixed amount of storage is
allocated causing overflow

19. What are the disadvantages of representing a stac
k or queue by a linked list? Ans:
i) A node in a
linked list (info and next field) occupies more storage than a corresponding element in an array. ii)
Additional time spent in managing the available list.

20. What is dangling pointer and how to avoid it? A
After a call to free(p) makes a subsequent
reference to *p illegal, i.e. though the storage to p is freed but the value of p(address) remain unchanged
.so the object at that address may be used as the value of *p (i.e. there is no way to detect the
egality).Here p is called dangling pointer. To avoid this it is better to set p to NULL after executing
free(p).The null pointer value doesn’t reference a storage location it is a pointer that doesn’t point to

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21. What are the disadvantages of l
inear list? Ans:
i) We cannot reach any of the nodes that precede
node (p) ii) If a list is traversed, the external pointer to the list must be persevered in order to reference the
list again

22. Define circular list? Ans:
In linear list the next field of

the last node contain a null pointer, when a
next field in the last node contain a pointer back to the first node it is called circular list. Advantages

From any point in the list it is possible to reach at any other point

23. What are the disadvantage
s of circular list? Ans:
i) We can’t traverse the list backward ii) If a
pointer to a node is given we cannot delete the node

24. Define double linked list? Ans:
It is a collection of data elements called nodes, where each node is
divided into three parts i) An info field that contains the information stored in the node ii) Left field that
contain pointer to node on left side iii) Right field that contain pointer t
o node on right side

25. Is it necessary to sort a file before searching a particular item ? Ans:
If less work is involved in
searching a element than to sort and then extract, then we don’t go for sort If frequent use of the file is
required for the purp
ose of retrieving specific element, it is more efficient to sort the file. Thus it depends
on situation.

26. What are the issues that hamper the efficiency in sorting a file? Ans:
The issues are i) Length of
time required by the programmer in coding a par
ticular sorting program ii) Amount of machine time
necessary for running the particular program iii)The amount of space neces
sary for the particularprogram

27. Calculate the efficiency of sequential search? Ans:
The number of comparisons depends on where

the record with the argument key appears in the table If it appears at first position then one comparison If
it appears at last position then n comparisons Average=(n+1)/2 comparisons Unsuccessful search n
comparisons Number of comparisons in any case is
O (n).

28. Is any implicit arguments are passed to a function when it is called? Ans:
Yes there is a set of
implicit arguments that contain information necessary for the function to execute and return correctly.
One of them is return address which is stor
ed within the function’s data area,

at the time of returning to
calling program the address is retrieved and the function branches to that location.

29. Parenthesis is never required in Postfix or Prefix expressions, why? Ans:
Parenthesis is not
because the order of the operators in the postfix /prefix expressions determines the actual order
of operations in evaluating the expression

30. List out the areas in which data structures are applied extensively? Ans:
Compiler Design,
Operating System, D
atabase Management System, Statistical analysis package, Numerical Analysis,
Graphics, Artificial Intelligence, Simulation

31. What are the major data structures used in the following areas : network data model &
Hierarchical data model. Ans:

y (i.e. Array of structures) Network data model

Hierarchical data model


32. If you are using C language to implement the heterogeneous linked list, what pointer type will
you use? Ans:
The heterogeneous linked list contains different data
types in its nodes and we need a link,
pointer to connect them. It is not possible to use ordinary pointers for this. So we go for void pointer.
Void pointer is capable of storing pointer to any type as it is a generic pointer type.

33. Minimum number of
queues needed to implement the priority queue? Ans:
Two. One queue is
used for actual storing of data and another for storing priorities.

34. What is the data structures used to perform recursion? Ans:
Stack. Because of its LIFO (Last In
First Out) proper
ty it remembers its ‘caller’ so knows whom to return when the function has to return.
Recursion makes use of system stack for storing the return addresses of the function calls. Every recursive
function has its equivalent iterative (non
recursive) function
. Even when such equivalent iterative
procedures are written, explicit stack is to be used.

35. What are the notations used in Evaluation of Arithmetic Expressions using prefix and postfix
forms? Ans:
Polish and Reverse Polish notations.

36. Convert the
expression ((A + B) * C


E) ^ (F + G)) to equivalent Prefix and Postfix
notations. Ans:
Prefix Notation: ^

* +ABC

DE + FG Postfix Notation: AB + C * DE

FG + ^

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37. Sorting is not possible by using which of the following methods? (a) Insertion

(b) Selection (c)
Exchange (d) Deletion

(d) Deletion. Using insertion we can perform insertion sort, using selection we can perform
selection sort, using exchange we can perform the bubble sort (and other similar sorting methods). But no
sorting met
hod can be done just using deletion.

38. List out few of the Application of tree data
structure? Ans:
The manipulation of Arithmetic
expression, Symbol Table construction, Syntax analysis.

39. List out few of the applications that make use of Multilinked Structures? Ans:
Sparse matrix,
Index generation.

40. in tree construction which is the suitable efficient data structure?
(A) Array (b) Linked list (c)
Stack (d) Queue (e) none
(b) Li
nked list

41. What is the type of the algorithm used in solving the 8 Queens problem? Ans:

42. In an AVL tree, at what condition the balancing is to be done? Ans:
If the ‘pivotal value’ (or the
‘Height factor’) is greater than 1 or less than


43. There are 8, 15, 13, 14 nodes were there in 4 different trees. Which of them could have formed a
full binary tree? Ans:
15 In general: There are 2n
1 nodes in a full binary tree.

By the method of elimination: Full binary trees contain odd number

of nodes. So there cannot be full
binary trees with 8 or 14 nodes, so rejected. With 13 nodes you can form a complete binary tree but not a
full binary tree. So the correct answer is 15.
Full and Complete binary trees are different. All full
binary trees are complete binary trees but not vice versa.

44. In RDBMS, what is the efficient data structure used in the internal storage representation? Ans:
B+ tree. Because in B+ tree, all the dat
a is stored only in leaf nodes, that makes searching easier. This
corresponds to the records that shall be stored in leaf nodes.

45. One of the following tree structures, which is, efficient considering space and time complexities?
a) Incomplete Binary Tr
ee. b) Complete Binary Tree. c) Full Binary Tree. Ans:
b) Complete Binary
Tree. By the method of elimination: Full binary tree loses its nature when operations of insertions and
deletions are done. For incomplete binary trees, extra property of complete bi
nary tree is maintained even
after operations like additions and deletions are done on it.

46. What is a spanning Tree? Ans:
A spanning tree is a tree associated with a network. All the nodes of
the graph appear on the tree once. A minimum spanning tree i
s a spanning tree organized so that the total
edge weight between nodes is minimized.

47. Does the minimum spanning tree of a graph give the shortest distance between any 2 specified
nodes? Ans:
No. Minimal spanning tree assures that the total weight of t
he tree is kept at its minimum.
But it doesn’t mean that the distance between any two nodes involved in the minimum
spanning tree is

48. Whether Linked List is linear or Non
linear data structure? Ans:
According to Storage Linked
List is a Non
ear one.



questions and answers

1.What is a Database? Ans:
A database is a collection of related data .A database is a logically coherent
collection of data with some inheren
t meaning.

2. What is DBMS? Ans:
Database Management system is a collection of programs that enables user to
create and maintain a database. Thus a DBMS is a general purposed s/w system that facilitates the process
of defining constructing and manipulatin
g a database for various applications. (Defining a data base
involves specifying the data types, structures and constraints for the data to be stored in the data database.
Constructing a data base is the process of storing data itself on some storage mediu
m that is controlled by
DBMS. Manipulating a database includes such functions as querying the data base to retrieve specific
data, updating the database to reflect the changes in the mini

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3. What is a Catalog? Ans:
A catalog is a table that contain

the information such as structure of each file
, the type and storage format of each data item and various constraints on the data . The information
stored in the catalog is called Metadata . Whenever a request is made to access a particular data, the
S s/w refers to the catalog to determine the structure of the file.

4. What is data ware housing & OLAP? Ans:
Data warehousing and OLAP (online analytical
processing ) systems are the techniques used in many companies to extract and analyze useful informa
from very large databases for decision making .

5. What is real time database technology? Ans:
These are all the techniques used in controlling
industrial and manufacturing processes.

6. What is program
data independence? Ans:
Unlike in the traditio
nal file sys. the structure of the data
files is stored in the DBMS catalog separately from the access programs . This property is called program
data independence.i.e. We needn’t to change the code of the DBMS if the structure of the data is changed
h is not supported by traditional file sys .

7. What is ORDBMS? Ans:
Object oriented RDBMS is a relational DBMS in which every thing is
treated as objects. User can define operations on data as a part of the database definition.

8. What is program
ion independence? Ans:
An operation is specified in two parts . 1. Interface
(operation name and data types of its arguments). 2. Implementation (the code part) The implementation
part can be changed without affecting the interface. This is called program
operation independence.

9. What is a view? Ans:
A view may be a subset of the database or it may contain virtual data that is
derived from the database files but is not explicitly stored .

10. What is OLTP? Ans:
Online transaction processing is an applica
tion that involve multiple database
accesses from different parts of the world . OLTP needs a multi
user DBMS s/w to ensure that concurrent
transactions operate correctly.

11. What is the job of DBA? Ans:
A database administrator is a person or a group responsible for
authorizing access to the database, for coordinating and monitoring its use, and for acquiring s/w and h/w
resources as needed.

12. Who are db designer? Ans:
Data base designers are responsib
le for identifying the data to be stored
in the database and for choosing appropriate structure to represent and store this data .

13. What are different types of end users? Ans:
1. Casual end
users 2. Naive or parametric end users 3.
Sophisticated end us
ers 4. Stand alone users.

14. What are the advantages of using a dbms? Ans:
1. Controlling redundancy. 2. Restricting
unauthorized access. 3. Providing persistent storage for program objects and data structures. 4. Permitting
inferencing and actions using

rules. 5. Providing multi
user interfaces. 6. Representing complex
relationships among data. 7. Enforcing integrity constraints. 8. Providing backups and recovery.

15. What are the disadvantages of using a dbms? Ans:
1. High initial investments in h/w, s
/w, and
training. 2. Generality that a DBMS provides for defining and processing data. 3. Overhead for providing
security, concurrency control, recovery, and integrity functions.

16. What is a data model? Ans:
It is a collection of concepts that can be us
ed to describe the structure of
a database. It provides necessary means to achieve this abstraction. By structure of a database we mean
the data types, relations, and constraints that should hold on the data.

17. What are different categories of data mode
ls? Ans:
1. High
level or conceptual data models. 2.
Representational data models. 3. Low
level or physical data models. High level data models provide the
concepts that are close to the way many users perceive data. Representational data models are provid
concepts that provide the concepts that may be understood by end users but that are not too far removed
from organization of data in the database. Physical data models describe the details of how data is stored
in the computers.

18. What is schema? Ans:
The description of a data base is called the database schema , which is
specified during database design and is not expected to change frequently . A displayed schema is called
schema diagram .We call each object in the schema as schema construct.

19. Wha
t are types of schema? Ans:
1. internal schema. 2. Conceptual schema. 3. External schemas or
user views.

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20. What is Data independency? Ans:
Data independency is defined as the capacity to change the
conceptual schema without having to change the schema a
t the next higher level. We can define two types
of data independence: 1. Logical data independence. 2. Physical data independence. LDI is the capacity to
change the conceptual schema without having to change external schemas or application programs. PDI i
the capacity to change the internal schema without having to change conceptual (or external) schemas.

21. What are different DBMS languages? Ans:
1. DDL (Data definition language) 2. SDL (Storage
definition language) 3. VDL (View definition language) 4.

DML (Data manipulation language)

22. What are different types of DBMS? Ans:
1. DBMS 2. RDBMS (Relational) 3. ORDBMS (Object
Relational) 4. DDBMS (Distributed) 5. FDBMS (Federated) 6. HDDBMS (Homogeneous) 7. HDBMS
(Hierarchical) 8. NDBMS (Networked)

What is an entity? Ans:
An entity is a thing in the real world with an independent existence.

24. What are attributes? Ans:
These are the particular properties that describe an entity.

25. What are diff. types of attributes? Ans:
1. Composite Vs simple a
ttributes. 2. Single valued Vs
valued attributes. 3. Stored Vs derived attribute. 4. Null valued attributes. 5. Complex attributes.

26. What is difference between entity set and entity type?

27. What is domain value or value set of an attribute? An
It is the set of values that may be assigned
to that attribute for each individual entities .

28. What is degree of a relationship? Ans:
The no of entities participating in that relation .

29. What is recursive relationship? Ans:
It is the relationshi
p where both the participating entities
belong to same entity type .

30. What are relationship constraints? Ans
: 1. Cardinality ratio. 2. Participation constraints.

1. What is Cardinality ratio? Ans:
The cardinality ratio for a binary relationship specif
ies the number
of relationship instances that an entity can participate in.

32. What is a Participation constraint? Ans:
The participation constraint specifies whether the
existence of an entity depends on its being related to another entity via the relat
ionship type. This is of
two types: 1. Total participation. 2. Partial participation.

33. What is a weak entity types? Ans:
The entity types that do not have key attributes of their own are
called weak entity types. Rests are called strong entity types .T
he entity that gives identity to a weak
entity is called owner entity. And the relationship is called identifying relationship. A weak entity type
always has a total participation constraint with respect to its identifying relationship.

34. What is an ER Diagram? Ans:
This data model is based on real world that consists of basic objects
called entities and of relationship among these objects. Entities are described in a database by a set of

35. What is an EER?

enhanced entity

relationship (EER)

model is a high
level or

data model incorporating extensions to the original


(ER) model, used in the
design of

The EER model includes all of the concepts introduced by the ER model.
tionally it includes the concepts of a

, along with the concepts of


36. What is specialization? Ans:
It is the process of defining a set of subclasses of an entity type where
each subclass contain all the attributes and relationships of the parent entity and may have ad
attributes and relationships which are specific to itself.

37. What is generalization? Ans:
It is the process of finding common attributes and relations of a
number of entities and defining a common super class for them.

38. What are constraints

on generalization and specialization? Ans:
1. disjoint ness constraints. 2.
Completeness constraints. Disjointness constraint specifies that the subclasses of the specialization must
be disjoint .i.e. an entity can be a member of at most one of the subcla
sses of the specialization. The
reverse of it is overlapping. Completeness constraint is a participation constraint which may be 1. Total 2.
Partial Total specialization constraint tells that each entity in the super class must be a member of some

in the specialization. And partial specialization constraint allows an entity not to belong to any of
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the subclasses .Thus we do have the following 4 types of constraints on specialization: 1. Disjoint, total

Disjoint, partial 3. Overlapping, total 4.
Overlapping, partial

39. What is a ternary relationship? Ans:
A relationship with a degree 3 is called a ternary relationship.

40. What is aggregation and association? Ans:
Aggregation is an abstraction concept for building
composite objects from their
component objects. The abstraction of association is used to associate
objects from several independent classes

41. What is RAID Technology? Ans:
Redundant array of inexpensive (or independent) disks. The main
goal of raid technology is to even out the widely different rates of performance improvement of disks
against those in memory and microprocessor. Raid technology employs the technique of data
striping to
achieve higher transfer rates.
42. What is Hashing technique? Ans:
This is a primary file organization
technique that provides very fast access to records on certain search conditions. The search condition
must be an equality condition on a s
ingle field, called hash field of the file. 1. Internal hashing 2. External
hashing 3. Extendible hashing 4. Linear hashing 5. Partitioned hashing

43. What are different types of relational constraints? Ans:
1. Domain constraints 2. Key constraints
3. Ent
ity integrity constraints 4. Referential integrity constraints Domain constraints specify that the value
of each attribute must be an atomic value from the domain of the attributes. Key constraints tell that no
two tuples can have the same combination of v
alues for all their attributes. Entity integrity constraint
states that no primary key value can be null. Referential integrity constraints states that a tuple in one
relation that refers to another relation must refer to an existing tuple in that relation

it is specified between
two relations and is used to maintain the consistency among tuples of the two relations.

44. What is difference between a super key, a key, a candidate key and a primary key? Ans:
A super
key specifies a uniqueness constrain that
no two distinct tuples in a state can have the same value for the
super key. Every relation has at least one default super key. A key is a minimal super key or the subset of
the super key which is obtained after removing redundancy. A relation schema may h
ave more than one
key .In this case each key is called a candidate key. One of the candidate key with minimum number of
attributes is chosen as primary key.

45. What is a foreign key? Ans:
A key of a relation schema is called as a foreign key if it is the

key of some other relation to which it is related to.

46. What is a transaction? Ans:
A transaction is a logical unit of database processing that includes one
or more database access operations.

47. What are the properties of transaction?

1. Ato
micity 2. Consistency preservation 3. Isolation 4. Durability (permanence)

48. What are the basic data base operations? Ans:
1. Write_item(x) 2. Read_item(x)

49. What are the disadvantages of not controlling concurrency? Ans:
1. Lost update problem 2.
porary update(Dirty read) problem 3. Incorrect summary problem

50. What are serial, non serial? Ans:
A schedule S is serial if, for every transaction T participating in
the schedule, all the operations of T is executed consecutively in the schedule, other
wise, the scheduleis
called non
serial schedule

51. What are conflict serializable schedules? Ans:
A schedule S of n transactions is serializable if it is
equivalent to some serial schedule of the same n transactions.
52. What is result equivalent? Ans:
schedules are called result equivalent if they produce the same final state of the data base.

53. What are conflict equivalent schedules? Ans:
Two schedules are said to be conflict equivalent if the
order of any two conflicting operations is the same i
n both schedules.

54. What is a conflict serializable schedule? Ans:
A schedule is called conflict serializable if it is
conflict equivalent to some serial schedule.

55. What is view equivalence? Ans:
Two schedules S and S’ are said to be view equivalent

if the
following three conditions hold : 1. Both S and S’ contain same set of transactions with same operations
in them. 2. If any read operation read(x) reads a value written by a write operation or the original value of
x the same conditions must hold i
n the other schedule for the same read(x) operation. 3. If an operation
write1(y) is the last operation to write the value of y in schedule S then the same operation must be the
last operation in schedule S’.

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56. What is view serializable? Ans:
A schedule

is said to be view serializable if it is view equivalent
with some serial schedule.

57. What are the various methods of controlling concurrency? Ans:
1. Locking 2. Time stamp
Locking data item to prevent multiple transactions from accessing the item conc
urrently. A time stamp is
a unique identifier for each transaction, generated by the system.

58. What is a lock? Ans
: A lock is a variable associated with a data item that describes the status of the
item with respect to the possible operations that can be

applied to it.

59. What are various types of locking techniques? Ans:
1. a binary lock 2. Shared/Exclusive lock 3.
Two phase locking

60. What is a binary lock? Ans:
A binary lock can have two states or values: 1. locked (1) 2.
unlocked(0) If locked it c
annot be accessed by any other operations, else can be.

61. What is shared or exclusive lock? Ans:
It implements multiple
mode lock. Allowing multiple
accesses for read operations but exclusive access for write operation.

62. Explain two phase locking? An
All the locking operations must precede the first unlock operation
in the transaction .It does have two phases: 1. expanding phase (Locks are issued) 2. Shrinking phase
(Locks are released)

63. What are different types of two phase lockings (2pl)? Ans:

1. Basic 2. Conservative 3. Strict 4.
Rigorous this is the basic technique of 2pl described above. Conservative 2pl requires a transaction to
lock all the items it accesses before the transaction begins its execution, by pre
declaring it’s read
set and
set. Strict 2pl guarantees that a transaction doesn’t release any of its exclusive locks until after it
commits or aborts. Rigorous guarantees that a transaction doesn’t release any of its locks (including
shared locks) until after it commits or aborts

64. What is a deadlock? Ans:
Dead lock occurs when each transaction T in a set of two or more
transactions is waiting for some item that is locked by some other transaction T’ in the set. Hence each
transaction is in a waiting queue, waiting for one of
the other transactions to release the lock on them.

65. What are triggers? Ans:
Triggers are the PL/SQL blocks definining an action the database should
take when some database related event occurs. Triggers may be used to supplement declarative referentia
integrity, to enforce complex business rules, or to audit changes to data.