May 2017

SECTION III-6: Internal Working of Computers

A step-by-step analysis of the process a CPU would go through to add three numbers is demonstrated below. Assume an imaginary CPU has registers called A, B. C, and D. It has an 8 bit of data bus and a 16 bit of address bus. Therefore, the CPU can access memory from addresses 0000 to FFFFH (for a total of 10000H locations). The action to be performed by the CPU is to put hexadecimal value 21 into register A, and then add to register A values 42H and 12H.

SECTION III-5: Inside Central Processing Units

A program stored in memory provides instructions to the CPU to perform an action. The action can simply be adding data such as payroll data or controlling a machine such as a robot. The function of the CPU is to fetch these instructions from memory and execute them. To perform the actions of fetch and execute, all CPU's are equipped with resources such as the following:


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