Buses:

• Execution of 1 instruction need the following 3 steps to be performed by the CPU:

I.  Fetch the contents of the memory location pointed at by the computer system. The contents of this location are interpreted as an instruction to be executed. Therefore, they are holed up in the instruction register (IR). Symbolically, it can be written as:

2. supposing that the memory is byte addressable .it increment the contents of the PC by 4, that is 

3.   Perform the actions mention by the instruction stored in the IR

• But, in cases wherever an instruction take place more than 1 word, steps 1 and 2 might be repeated as several times as essential to fetch the complete instruction.
• 2 first steps are typically referred to as the fetch phase.
• Step 3 constitutes  in the execution phase

Most of the operation in step 1 to 3 denoted earlier can be carried out by performing one or more of the following function

However, in cases where an instruction takes place more than 1 word, steps 1 and 2 might be

repeated as several times as essential to fetch the complete instruction.

• 2 first steps are usually referred to as the fetch phase.
• Step 3 constitutes in the execution phase

Fetch the contents of a specific memory location and load them into a CPU Register

• Hold up a word of data from a CPU register into a particular given memory location.
• Transfer a word of data from 1 CPU register to another or to ALU.
• Perform logic or arithmetic operation, and store the outcome in a CPU register.