Digital Information Technology

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2 Νοε 2013 (πριν από 3 χρόνια και 7 μήνες)

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Introduction

Digital Information Technology

Learning Objectives


Identify the major hardware components of a computer
system


Describe the evolution of computer processor technology


Differentiate the various types of input and output
technologies and their uses


Identify the characteristics of computer memory and
memory capacity terminology


Describe the design and functioning of the central processing
unit


Discuss the concept of digital technology and how it impacts
storage and processing for character data, numbers, and
various forms of multimedia


Introduction


E
-
commerce is enabled by a wide range of digital information
technologies including computer hardware, software, databases,
networks, the Internet/Web, and various forms of multimedia


In this discussion we focus on the components of a computer
system, and how these components function, to gain an
understanding of the capabilities and limitations of digital
information technology


A computer system consists of the following:


Central processing unit (CPU)


Primary storage


Secondary storage


Input technologies


Output technologies


Communication technologies

Computer System Components

Processor Technology Evolution


Computer processing hardware technology has evolved quite
dramatically in the past 60+ years


The generations of hardware technology include:


1
st

generation


Vacuum tubes (1946
-
1956)


2
nd

generation


Transistors (1957
-
1963)


3
rd

generation


Integrated circuits (1964
-
1979)


4
th

generation


Ultra
-
large
-
scale integrated circuits (1980
-
present)


5
th

generation


Massively parallel processing


What are the trends associated with the evolution of
hardware technology?

Processor Speed Terminology


As the speed of computer processors, data access devices,
and data transmission continues to increase, new terminology
is required to compare current capabilities with older
technologies


Time in a computer environment is represented in fractions
of a second


The following are common measures of time:


Millisecond = 1/1000 second


Microsecond = 1/1,000,000 second


Nanosecond = 1/1,000,000,000 second


Picosecond

= 1/1,000,000,000,000 second


Input and Output Devices


Input and output (I/O) devices enable human
-
computer
interaction (HCI)


Input devices enable human data and actions to be converted
into a computer
-
understandable format


Examples include a keyboard and a mouse


Output devices translate computer representations of data
into a human
-
understandable format (text, images, sound,
etc.)


Examples include monitors and printers


Input and output devices have traditionally been physical
devices, but the trend is toward more virtual I/O devices

Computer Memory


Storing characters, numbers, images, and other multimedia
files for organizations and individuals requires a massive
amount of computer memory


Luckily, as computer hardware technology has evolved, so
has the computer memory capacity required to support new
applications


Example secondary storage devices include internal
computer hard drives, external hard drives, CD/DVD, flash
memory devices, and cloud
-
based storage services


As storage requirements have continued to increase, new
terminology is required to describe digital storage capacity


Hierarchy of Memory Capacity


Kilobyte


Approximately one thousand bytes


A kilobyte is actually 1024 bytes (why?)


Megabyte


One million (10
6
) bytes


Gigabyte


One billion (10
9
) bytes


Terabyte


One trillion (10
12
) bytes


Petabyte


One quadrillion (10
15
) bytes


Exabyte


One quintillion (10
18
) bytes


The Central Processing Unit


The central processing unit (CPU) performs the actual
computation inside any computer


The CPU is a microprocessor made up of millions of
microscopic transistors embedded in a circuit on a silicon
wafer (or chip)


The CPU and all components of a computer system process
and store data using digital technology


What is the unique characteristic of “digital” technology?

How the CPU Works

Digital Technology


Today’s computers are based on integrated circuits (chips),
each of which includes millions of subminiature transistors


Each transistor can be in either an “on” or “off ” position


The “on
-
off ” states of transistors are described using binary
number system where each binary digit, or bit, has a value of
either 1 or 0


This digital concept enables the storage and processing of
characters, numbers, and various forms of multimedia


Character Representation and
Processing


A sufficient number of bits to represent specific characters


letters, numbers, and special symbols


is known as a byte, usually
8 bits


Because a bit has only two states, 0 or 1, the bits comprising a byte
can represent any of 2
8
, or 256, unique characters


The two most commonly used coding schemes are:


For microcomputers
-

the American National Standard Code for
Information Interchange (ASCII), pronounced “ask
-
ee



For mainframe computers


the Extended Binary Coded Decimal
Interchange Code (EBCDIC), pronounced “
ebsa
-
dick”


ASCII and EBCDIC are sufficient for English and Western
European languages but are not large enough for Asian and other
languages that use different alphabets


Number Representation and
Processing


Numbers in a computer are stored and processed using
binary (base 2) representations


Why?


Humans store numbers and do mathematical computations
using a decimal representation (base 10)


Why?


The ALU in a CPU can perform basic computations such as
add, subtract, multiply, divide, compare, and determine
whether a number is positive, negative, or zero


How does a computer perform these numerical processes?

Image Representation and Processing


Pictures are represented by a grid overlay of the picture


Each dot on a screen, or pixel, can display one color


More pixels per square inch improve the picture clarity, but also
take more storage space and require more time to download


Image Representation and Processing
(cont.)


Each pixel can be displayed in a wide range of colors by
varying the intensity of red, green and blue displayed for each
pixel


Two common image formats are:


Graphics Interchange Format (GIF), 256 colors


Joint Photographic Experts Group (JPEG), 16.7 million colors


Video Representation and Processing


How is video storage and processing different from image
storage and processing?


Video files are digitally stored as a series of interrelated still
images


The file sizes vary depending on format, frame size, and
frame rate (frames per second, fps)


A typical fps rate is about 30, fast enough to fool the human
eye and make the series of still images appear as natural
movement

Audio Representation and Processing


Every sound (wave) can be described by two characteristics


amplitude (loudness) and frequency (pitch)


Digital recording measures the sound’s characteristics at
discrete moments in time


The conversion method from analog to digital affects the
sound quality and the file size, it has three components:


Sampling rate


number of measurements in a period of time
(KHz)


Sampling resolution


precision in measuring the sound within
each sample (8
-
bit, 16
-
bit, etc.)


Channels


mono or stereo


For example, a telephone is 8KHz, 8
-
bit, mono; and a CD is
44KHz, 16
-
bit, stereo