Control unit (CU) and arithmetic logic unit (ALU) of a computer system are together known as the central processing unit .It is the brain of a computer system . In human body, the brain takes all major decisions and all of the body function as direct by the brain. Similarly, in a computer system, the CPU performs all major calculation and comparosions , and also activates and controls the operations of other units of the computer system .
A computer performs all calculation and comparison operations in the ALU. During processing of a job, the computer transfers data and instructions stored in its primary storage to ALU as and when needed. ALU does the processing and the computer temporarily transfers the intermediate result generated there back to primary storage unit needed later. hence, data may move back and forth several times between primary storage and ALU before processing of the job is over.
Almost all alus are designed to perform the basic arithmetic operations(add, subtract, and divide) and logic operations or comparisons such as, less than, equal to, and greater than.
COMPUTERLEARNING 