COMPUTER ARCHITECTURE
Recommended Text
1
Computer Organization and Architecture
by William Stallings
2
Structured Computer Organisation
Andrew S. Tanenbaum
A Computer is
• A programmable machine. It can execute or run a prerecorded list of instructions which follow certain rules (a
program).
• Modern computers are electronic and digital. The actual
machinery -- wires, transistors , and circuits -- is called
hardware; the instructions and data are called software.
Computer System
• Hardware
• Software
– OS
– Application SW
• Live ware
Components of a Computer System
• Computer hardware provides the physical mechanisms to
process, store, and input /output data. Includes CPU,
memory, I/O devices
• Software provides instructions to tell the hardware what
tasks to perform. It includes system (eg Windows XP) and
application (eg Excel) software
Data in the computer may be representing numbers,
characters, graphics etc but is always kept in a form that the
hardware and software can manipulate.
What are the major Hardware components
of the computer ?
•
•
•
•
•
•
•
•
central processing unit
primary memory
secondary storage
input devices
output devices
communications devices
I/O cards
System Bus
Block Diagram of a Computer
Main Memory
CPU
IO Modules
IOD
IOD
IOD
Computer Hardware
1
Hardware- the CPU
• CPU performs actual processing of data, according to
instructions from programs.
• Data and programs are stored in primary and secondary
memory, and moved to and from CPU as required.
• Signals representing data and instructions travel between
system components along electronic pathways, called buses.
Capacity of bus is critical to system performance.
Central Processing Unit ( CPU)
1. Acting as the brain of the computer’
2. Currently the Intel-Pentium microprocessor is the
most common CPU though there are many types
Hardware - The Processor
• The CPU is a general purpose processor that performs data
manipulation and/or transformation functions including
computations, comparisons and data movement.
• The CPU consists of 3 main parts:
– ALU - where arithmetic and logical operations performed
– Control Unit - controls data movement and execution of
instructions
– Registers - small high speed storage areas
Components of a computer system
Computer Hardware
2
Hardware - memory
• Memory - Purpose of memory is data storage. Two major
types of memory :
• Primary memory - to hold data and instructions during
processing
– eg RAM. Relatively limited capacity and volatile
• Secondary memory - to provide permanent long term
storage
– eg hard disk. High capacity and non-volatile
Main Memory (RAM)
1. Different from disk storage
2. used to temporarily store Data
3. in modern computers memory is 512 MB.
Hardware- memory
• Digital computers deal with data in binary form - all data is
represented using just two digits - 1 or 0. Letters and other
symbols are assigned unique binary codes.
• Primary memory consists of a set of locations defined by
sequentially numbered addresses. Each location contains a
binary number that can be interpreted as data or an
instruction.

Memory locations are called words. Words are 8 bits
(one byte) in size, or a multiple of 8. Common word sizes are
16, 32 and 64 bits.
0
1 0 0 1 0 0 0 1
1
1 1 0 1 0 0 1 1
2
0 1 0 0 0 0 0 0
3
1 0 1 0 0 1 1 1
4
1 1 1 0 1 0 1 0
5
1 1 0 0 1 0 1 0
Memory locations, using an 8 bit word
Hardware - memory
•
Memory is commonly measured in multiples of bits and
bytes.
1 bit = 1 binary digit (0 or 1).
1.
1 byte = 8 bits
2.
1KB = 1024 bytes = 210
3.
1MB = 1024 KB= 220
4.
1GB = 1024 MB = 230
5.
1TB = 1024 GB = 240
Hardware - memory
• Secondary storage consists of non-volatile high-capacity
devices to store programs and data not currently required by
CPU.
• Hard and floppy disks, and tapes store data as magnetized
spots.
• CD’s and DVD’s store data as pits or surface marks
detectable by laser light.
3
Hardware – I/O
• Input Devices collect & translate raw data into form useable
by computer. e.g keyboard accepts letters and numbers and
converts them to a binary code such as Unicode.
• Output devices produce results in useable form for user (or
another device). e.g. monitor converts binary codes to
characters and images, whilst modem converts digital data
to analog form for transmission over telephone lines.
Hardware – I/O Peripherals
1 Input Devices
• Mouse
• Keyboard
2 Output Devices
• Monitor (VDU)
• Printer
3 Secondary Storage Devices
• Hard Disk
• CD / DVD / Floppy
I/O Hardware
4
Hardware - I/O Modules
•
Interface between System Bus and other Peripherals
•
example
–
Sound cards
–
Video cards
–
Network cards
–
PCI cards
5
Hardware - System Bus
• series of electronic path ways and connecting other
components of the computer.
Structure - Top Level
Peripherals
Computer
Central
Processing
Unit
Computer
Systems
Interconnection
Input
Output
Communication
lines
Main
Memory
Structure - The CPU
CPU
Computer
Arithmetic
and
Login Unit
Registers
I/O
System
Bus
Memory
CPU
Internal CPU
Interconnection
Control
Unit
What are Computer Ports ?
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•
Connection point
examples
1. Serial port (Com)
2. Parallel Port
3. USB port
4. Ethernet Port
Basic concepts - communication
• Most modern computers no longer operate in isolation they connect to other computers via modem or a network.
• To enable this communication, specialized hardware and
software must be added to computers.
• In combination with other devices such as telephones,
cabling, satellites, microwaves etc. , a communications
network is created
Types of computers
• Personal Computer
– Microprocessor
• Mini computer
• Main frame
• Super computer
Types of computers
• personal computer : A small, single-user computer based
on a microprocessor. In addition to the microprocessor, a
personal computer has a keyboard for entering data, a
monitor for displaying information, and a storage device for
saving data.
• minicomputer : A multi-user computer capable of
supporting from 10 to hundreds of users simultaneously.
• mainframe : A powerful multi-user computer capable of
supporting many hundreds or thousands of users
simultaneously.
• supercomputer : An extremely fast computer that can
perform hundreds of millions of instructions per second.
What are Major functions of a Computer ?
1
2
3
4
Data processing
Data storage
Data movement
Control
Functional view
Data
Storage
Facility
Data
Movement
Apparatus
Control
Mechanism
Data
Processing
Facility
Operations (1)
• Data movement
– e.g. keyboard to screen
Data
Movement
Apparatus
Data
Storage
Facility
Control
Mechanism
Data
Processing
Facility
Operations (2)
• Storage
– e.g. Internet download to disk
Data
Movement
Apparatus
Data
Storage
Facility
Control
Mechanism
Data
Processing
Facility
Operation (3)
• Processing from/to storage
– e.g. updating bank statement
Data
Movement
Apparatus
Data
Storage
Facility
Control
Mechanism
Data
Processing
Facility
Operation (4)
• Processing from storage to I/O
– e.g. printing a bank statement
Data
Movement
Apparatus
Data
Storage
Facility
Control
Mechanism
Data
Processing
Facility