1. COMPUTER
ARCHITECTURE

2. Computer Hardware
All the physical components of computer are
called Computer Hardware
OR
All the touchable parts of computer are called
Computer Hardware
For example: keyboard, mouse, hard disk,
RAM, ROM, CPU

3. Basic architecture of computer
means how computer hardware
works, how hardware components
of computer system connect to
each other.
Computer Architecture

4. Computer Architecture
F.D
H.D
Monitor
Key
Board
Mouse
DATA BUS
ADDRESS & CONTROL BUS
Cache
Math
coprocessor
Clock
CPU
CU
ALU
ROM RAM
Prin
ter

5. Computer Architecture
System Unit

6. Computer Architecture
System Unit
System may be defined as a set of related components.
So,
System unit may be defined as follows:
A computer case also known as a "computer chassis", "tower",
"system unit", "base unit" or simply "case" and sometimes
incorrectly referred to as the "CPU" or "hard drive", is the
enclosure that contains most of the components of a computer.
A system unit is the part of a computer that houses the primary
devices that perform operations and produce results for complex
calculations. It includes the motherboard, CPU, RAM and other
components, as well as the case in which these devices are
housed.

7. Computer Architecture
Motherboard / Mainboard
It is the main circuit board in computer system. It
contains all the circuits and connectors. All
devices attached with the computer are basically
attached with the motherboard through
connectors.

8. Computer Architecture
CPU (Central Processing Unit)
•CPU is the central part of the computer system.
It is also called brain of computer system. As in
human body, the brain takes all major decisions
and other parts of the body perform different
functions as directed by brain.

9. Computer Architecture
Control Unit (CU)
Control unit controls overall operations of
computer. The CU fetches instructions from main
memory (RAM), interprets them, fetches required
data and tell ALU what to do.
Arithmetic Logic Unit (ALU)
This unit handles the arithmetic and logic
functions with in the CPU. It takes instructions
decoded by the Control Unit, and performs
actions as directed by control unit.
CPU

10. Computer Architecture
Cache Memory
Cache memory is a special type of memory
provided within a CPU to speed up it processing
speed. It works just like RAM but it is less in
storage capacity as compared to RAM.
Registers
Registers are special purpose high-speed single
storage locations. In the CPU, each register is
wired to perform a specific role.
CPU

11. Computer Architecture
Buses
A Bus is a group of electrical conductors that
carry computer signals from one location to
another. Buses are the computer's transporters.
CPU

12. Computer Architecture
Performance of CPU
Performance of CPU can be measured by following
factors:
Register Size
A CPU with large register size can store large
amount of data. Hence greater the register size there
will be better performance of CPU.
Instruction Set Size
A CPU can execute only a limited number of
instructions for all types of operations. That set of
instructions is called instruction. The greater the
instruction set size there will be better performance
of CPU.

13. Computer Architecture
Performance of CPU
Clock Speed
The CPU clock can generate from 100 to 1000
million ticks in a second. The number of ticks
generated in a second by a CPU is called the
frequency of that CPU. The unit to measure the
frequency is Hertz.

14. Computer Architecture
How CPU executes an instruction ?
Following four steps are involved in the
execution of an instruction:
Instruction Fetch: First of all, the instruction, to
be executed is fetched in CPU from RAM (main
memory). CU performs this function.
Interpret Instruction:
In this stage, CPU interpret/decode instruction.
CPU decides what action is to be taken for the
execution of the instruction. CU performs this
function.

15. Computer Architecture
How CPU executes an instruction ?
Data Fetch: If some data is required for the
execution of the instruction, that data will be
fetched from the memory (where it resides) and
loaded into CPU register. CU performs this
operation of fetching data from memory and
loads it in CPU register.
Execute Instruction:
When an instruction has been decoded, and
required data is fetched, then the CPU actually
executes the instruction. Normally, ALU executes
most of the instructions.

16. Computer Architecture
RAM(Random Access Memory)

17. Computer Architecture
RAM stands for Random Access Memory because
it is possible to randomly select and use any location
of this memory to directly store and retrieve data and
instruction.
Why RAM is called Main Memory?
RAM is also called main memory or primary memory
because CPU directly communicates with RAM. All
the data or instructions that we enter into a computer
directly goes to RAM and after executing the
instructions final results goes to RAM from where
results are gone to out put device.
RAM

18. Temporary/Volatile nature:
As soon as the computer is switched off all the
data stored in RAM is washed out. That’s why
RAM is also called volatile memory or temporary
memory.
Computer Architecture

19. Types of RAM
DRAM
DRAM stands for Dynamic RAM. It is a popular
type of RAM and is mostly used in computer.
DRAM is refreshed many times in a second
that’s why it is relatively slower than SRAM.
However it is cheaper, easily available and
requires less power.
Computer Architecture

20. SRAM
SRAM stands for Static RAM. SRAM is not so
popular because it is expensive and requires
more space and power than DRAM. SRAM is
faster than DRAM because it does not have to
refresh many times in a second.
Example:
Cache Memory
Computer Architecture

21. Computer Architecture
ROM(Read Only Memory)
ROM stands for Read Only Memory. It is the
type of memory where those programs and data
are kept which needs no change. The data once
stored here can’t be changed or modified. It is
also not possible to write new information into
ROM. This is the reason why it is called Read
Only Memory.

22. Non-Volatile Nature:
ROM stores data and instructions permanently
when the power is turned off, the instructions
stored in ROM are not lost.
BIOS
BIOS stands for Basic Input Output System. It is
the software that resides in ROM and is stored in
ROM at the manufacturing time of ROM.
Computer Architecture

23. Importance of ROM
ROM chip is fixed on motherboard and cannot
be removed. When computer is switched on, the
instructions stored in ROM are first loaded in to
the RAM for execution. The basic purpose of
these instructions (BIOS) is to prepare computer
system to start successfully.
After that execution, necessary files of operating
system are loaded in to the RAM. This whole
process is also called “booting” of computer
system.
Computer Architecture

24. PROM
PROM stands for Programmable Read Only
Memory. Computer system manufacturer
provides ROM chips and it is not possible for a
customer to modify the programs stored insides
the ROM chip.
EPROM
EPROM stands for Erasable Programmable
Read Only Memory. As the name implies, it is
possible to erase information stored in an
EPROM chip and the chip can be reprogrammed
to store new information using a special prom-
programmer facility.
Computer Architecture
Types of ROM

25. EEPROM
EEPROM stands for Electrically Erasable
Programmable Read Only Memory. This type of
ROM chip can be used several times by using
special electrical devices.
Uses
R&D personnel mainly use EPROM because
they frequently change the micro programs to
test the efficiency of the computer system with
new programs.
Computer Architecture
Types of ROM

26. Output
Hard
Disk
Inpu
t
RA
M
CPU
Computer Architecture
Interaction of RAM and
CPU
Cache

27. Hard Disk Drive
It is a popular secondary storage medium uses
now a days that no PC is assembled without it. It
exists in almost every computer system that is
used. It is also called fixed disk.
Computer Architecture

28. Floppy Disk
Floppy disk is also called simply a diskette or disk.
It is a small flexible plastic disk that is coated with
magnetic material. It was invented by IBM in early
1960s.
Uses:
Now a days usually floppy disks are used to
transfer small amount of data from one computer to
another computer.
Computer Architecture

29. Keyboard
Keyboard is the most widely used input device.
It is used to enter data and program instructions
into the computer.
Mouse
Mouse is also an important input device. It is
used for controlling screen cursor.
Computer Architecture

30. Monitor
The monitor or Visual Display Unit (VDU) is the
most commonly used output device. It is like a
TV screen. It can display alphanumeric
characters, special characters and graphics.
The output provided by monitor is called ‘soft
copy’.
Computer Architecture

31. Printer
Mouse is also an important input device. It is
used for controlling screen cursor.
Printers are used to produce output in the form
of text and graphics on paper.
The output on a paper is called hardcopy.
Computer Architecture