Functional Units of Computer System

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Functional Units of Computer System

In order to carry out the operations the computer allocates the task between its various functional units of computer system. The computer system is divided into three separate units for its operation. They are

Central Processing Unit (CPU) 

Most commonly, the ALU, CU and memory functional unit of a computer system are jointly known as the central processing unit. CPU is also known as the electronic brain of any computer system. It is just like brain but takes all major decisions, makes all sorts of calculations and directs different parts of the computer functions by activating and controlling the operations. The overall process how fast completed is determined on the speed of processor or clock speed of CPU. 

Clock Speed of Processor 

Clock speed is the rate at which a processor can complete a processing cycle. It is typically measured in megahertz or gigahertz. One megahertz is equal to one million cycles per second, while one gigahertz equals one billion cycles per second. This means a 1.8 GHz processor has twice the clock speed of a 900  MHz processor. 

The major functions of CPU are: 

• To control the flow of data by sending and receiving from the required components. 
• To execute and control program instructions. 
• To place the data and instructions into the memory during the time of processing. 
• To coordinate with operating system and assist to control peripheral devices. 

CPU has the following sub units in the computer systems: 

i. Arithmetic Logical Unit (ALU) 

After we enter data through the input device it is stored in the primary storage unit. The actual processing of the data and instructions are performed by Arithmetic Logical Unit. The major operations performed by the ALU are addition, subtraction, multiplication, division, logical and comparison operations. Data is transferred to ALU from storage unit when required. After processing the output is returned back to storage unit for further processing or getting stored. 

The major functions of ALU are ; 

1. To perform arithmetic operations such as addition, subtraction, multiplication, division on data. 
2. To  perform logical operation on data and expressions by mean of comparisons then take necessary decisions. 

ii. Control Unit (CU) 

The next functional unit of computer system is the Control Unit, which acts like the supervisor seeing that brings are done in proper approach. Control Unit is responsible for coordinating various operations using time signal. This unit determines the sequence in which computer programs and instructions are executed. Things like processing of programs stored in the main memory, interpretation of the instructions and issuing of signals for other units of the computer to execute them. It also acts as a switch board operator when several users access the computer simultaneously. Thereby it coordinates the activities of computer's peripheral equipment as they perform the input and output.

The major functions of CU are:

• To transfer entered data from input device to memory unit.
• To receive data and instructions from memory
• To decode the instructions in actual form.
• To activate and instruct the required circuit for related jobs.

ii. Memory unit:

The memory unit is also known as main or primary memory. It stores information (i.e instructions, data and intermediate final result of processing ) that arrives via the input unit so that information is made available to the appropriate residence for further processing after which they can be presented to the user via the output unit.

The basic functions of memory unit are:

• To hold the data and instructions temporary basis this is being executed on.
• To speed up the rate of data processing and transfer.
• To hold the address of active memory.
• To accumulate the results and data to be operated upon.