1. Components of Computer

2. Introduction Physical parts of the computer
Touch, see and feel the hardware
Consists of electronic circuits and mechanical components to perform various functions in the computer
The hardware components are:
Input Devices
Output Devices
Central Processing Unit
Memory Unit
Storage Devices

3. Computer System

4. Computer System

5. Central Processing Unit
Main component of the computer
Also called processor
Brain of the computer
Performs all the operations on the data according to program’s instruction
It executes the program instructions and tells other parts of the computer what to do
CPU fetches instructions of program from main memory and executes them one by one
CPU also has the ability to decide which instruction will be executed next

6. Central Processing Unit
Speed of the CPU is measured in Mega Hertz or Giga Hertz
CPU is divided into two parts or sub-units
Control Unit (CU)
Arithmetic Logic Unit (ALU)

7. Central Processing Unit

8. Control Unit Most important component of the CPU
Controls and coordinates all the activities of all other units of the computer
Considered as logical hub of the computer
Acts as central nervous system for other components of the computer
For example, the control unit receives the data and instructions from the input device and stores them in main memory
It perform all these functions by issuing commands to the relevant unit of the computer

9. Control Unit
Also controls the execution of the instructions given to the computer
Fetches the instruction and data from main memory
Decodes and executes the instruction one by one

10. Arithmetic Logic Unit Another important component of CPU
Performs the arithmetic and logical operations on the data
When the control unit encounters an instruction related to perform arithmetic or logical operation on data, it passes that instruction to the ALU
ALU consists of a number of registers and adder circuits
A register is a temporary storage device, which holds data and instruction as long as it is being interpreted and executed

11. Arithmetic Logic Unit
When the data and instruction are fetched from the main memory for processing, these have to be stored in one of the registers of the CPU

12. Machine Cycle or Instruction Cycle

13. Pipelining
In some computer, the control unit completes all four stages of the machine cycle before beginning work on the next instruction
Most of the modern PCs support a concept called pipelining
Parallel work known as pipelining
Pipelining is a technique used to improve the execution throughput of a CPU by using the processor resources in a more efficient manner.

14. Pipelining

15. Registers
A processor contains high speed and small sized locations, called registers
Temporarily hold data and instruction during processing
Size of register is 2 to 4 bytes
May hold a program instruction while it is being processed by CPU
May Hold the results of calculation
Part of processor, but not part of main memory or storage devices

16. Types of Registers Memory Address Register (MAR)
Memory Buffer Register (MBR)
Instruction Pointer Register
Instruction Register
Accumulator Register
Input/Output Register (I/O)
Stack Control Register
Flag Register

17. References
Introduction to Information Technology by Riaz Shahid, CM Aslam and Safia Iftikhar