by • 17/11/2012 • GeneralComments (0)545


A CPU is an integrated circuit resides on a single chip which interprets & executes program instructions as well as where data is manipulated.


Every CPU has three basic parts:

1. Control Unit

Data flows both in and out of the CPU. Control unit is a logical hub which directs the flow of data in such a way that it sequences the instructions of data, receives from memory, from happening simultaneously. Doing so, control unit also uses timing in sequencing those instructions.


2. Arithmetic-Logic Unit

It is the part of a CPU where all arithmetic and logical functions are performed. The arithmetic functions include addition, subtraction, multiplication, and division. The logical functions include comparisons where numbers or conditions are compared to each other such as>, <, =, etc.


3. Memory Unit

The memory unit is such an internal memory of a computer CPU which needs to have millions of bytes of space where it can hold programs and the being manipulated while they are being used. It provides temporary storage as well as permanent.


Machine Cycle of CPU

Each time the CPU executes an instruction, it takes a series of steps. The complete series of steps is called a machine cycle. A machine cycle can be divided into two smaller cycles. These are instruction cycle and execution cycle.

1. Instruction cycle:

In instruction cycle CPU takes two steps:


a. Fetching:

Before the CPU can execute an instruction, the control unit must retrieve or fetch a command or data from the computer’s memory.


b. Decoding:

Before a command can be executed, the control unit must decode the command into instruction set.


2. Execution cycle:

In execution cycle CPU also takes two steps:


a. Executing:

When the command is executed, the CPU carried out the instructions in order by converting them into macrocode.


b. Storing:

The CPU may be required to store the result of an instruction in memory.

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