Computer Organization
What is a Digital
Computer?
Ø A digital computer is a fast electronic
calculating machine that accepts digitized
input information, processes it according to
a list of internally stored instructions, and
produces the resulting output information.
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Computer Organization
Types of Computers
Ø Personal Computers
Ø Workstations
Ø Mainframes
Ø Supercomputers
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Computer Organization
Functional Units of a
Computer
Arithmetic
Input and
Logic
Memory
Output Control
I/O Processor
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Computer Organization
Input Unit
Ø The Input Unit accepts coded information
from human operators or from other
computers.
Ø Examples:
v keyboard, joystick, mouse, input pen,
touch screen, trackball, scanner, bar
code readers, microphone, floppy
disks, magnetic tapes, compact disks
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Computer Organization
The Memory Unit –
Primary Storage
Ø Primary Storage or Main Memory. This
is where programs are stored during their
execution. The MM is a fast memory
capable of operating at electronic speeds.
Ø The information in MM is often processed
in groups of fixed size called words.
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Computer Organization
The Memory Unit –
Primary Storage
Memory Address of 1st
0
Location Memory Location
1
2
.
.
.
4,194,302
4,194,303
To provide easy access to any word in MM, a
distinct address is associated with each word
location. Addresses are numbers that identify
successive locations.
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Computer Organization
Main Memory Divisions
Ø MM is subdivided into the following:
v Input Storage Area
v Working Storage Space
v Output Storage Area
v Program Storage Area
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Computer Organization
Memory Unit – Secondary
Storage
Ø Secondary Storage or Auxiliary Storage.
v This is used when large amounts of
data have to be stored (on a more
permanent basis), particularly if some
of the data need not be accessed very
frequently.
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Computer Organization
Processing Unit
Ø Also called the Central Processing Unit
(CPU) or Central Processor.
Ø It contains a number of high-speed (10
times faster than MM) storage elements
called registers that are used for
temporary storage of frequently used
operands.
Ø The CPU is composed of the Arithmetic-
Logic Unit (ALU) and the Control Unit
(CU).
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Computer Organization
Output Unit
Ø It sends processed results to the outside
world.
Ø Examples:
v Display screens, printers, plotters,
modems, microfilms, synthesizers,
high-tech blackboards, film recorders
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Computer Organization
Basic Operation of a
Computer
Ø The operation of a computer can be
summarized as follows:
1. The computer accepts information.
2. Information stored in the memory is
fetched, under program control, into
an arithmetic and logic unit, where it is
processed.
3. Processed information leaves the
computer through an output unit.
4. All activities inside the machine are
directed by the control unit.
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Computer Organization
Basic Concepts of
Computer Architecture
Ø Computer Architecture is the design of
computers, including their instruction sets,
hardware components, and system
organization.
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Computer Organization
Types of Programming
Language
Ø The different types of programming
languages are as follows:
v Machine Language
v Assembly Language
v High-level Language
v 4GL Language
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Computer Organization
Machine Language
Ø The natural or primitive language that the
computer actually understands. This
programming language consists of 0’s and
1’s which makes programming very
difficult.
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Computer Organization
Assembly Language
Ø A programming language that uses
“abbreviations” or mnemonics in place of
binary patterns in order to make the task of
programming easier.
Ø An assembler is used to translate
assembly language mnemonics into
machine language.
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Computer Organization
High-Level Language
Ø A programming language that uses
English-like commands or instructions.
High-level languages are the easiest to use
and contains many complicated or
advanced instructions.
Ø A compiler is used to translate high-level
language instructions into machine
language.
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Computer Organization
Fourth Generation
Language
Ø A fourth-generation programming language
(or 4GL) is a programming language
designed with a specific purpose in mind
such as the development of commercial
business software.
Ø All 4GLs are designed to reduce:
v programming effort.
v the time it takes to develop software.
v the cost of software development.
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Computer Organization
Advantages of High-Level
Languages
Ø Advantages of using high-level languages
over low-level languages:
1. Easy to Learn
2. Predefined Functions
3. Portability
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Computer Organization
Advantages of Low-Level
Languages
Ø Advantages of using low-level languages
over high-level languages:
1. Compact Code
2. Speed
3. Flexible
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