CPU
The CPU is the brain of a computer. It primary function is to execute programs. Beside executing programs, the CPU also controls the operation of all other component such as memory, input and output devices. Under its control, programs and data are stored in the memory and displayed on the CRT screen or printed on the printer.
The CPU of a small computer is a microprocessor. Fig . show the schematic diagram of a microcomputer. The CPU of a large computer contains a number of microprocessor and other ICs on one or more circuit boards. Each microprocessor in a large CPU performs a specific task.
Fig. shows the schematic diagram of a CPU or microprocessor. The major sections of a CPU are:
(1) Arithmetic and Logic Unit (ALU)
The function of a ALU is to perform arithmetic and logic operations such as addition, subtraction, multiplication and division; AND, OR, NOT (complement) and EXECLUSIVE OR operations. It also perform increment, decrement, shift and clear operations.
(2) Timing and Control Unit
The timing and control unit generates timing and control signals necessary for the execution of instructions. It provides status, control and timing signals necessary for the operation of other parts of the CPU, memory and I/O devices. It controls the entire operation of a computer. It is actually the control section of the CPU, which acts as the brain of a computer.
(3) Accumulator, General and Special Purpose Registers
The accumulator is a register which holds one of the operands prior to the execution of an instruction and receives result of the most arithmetic and logical operations. It is the most frequently used register. Some CPUs contain a single accumulator, other contain several accumulators. General purpose registers store data and intermediate results during the execution of a program. They are accessible to programmers through instructions if they are working in an assembly language. Special purpose registers are not accessible to users. They are used by the computer for different purpose during program execution. Examples of special purpose registers are: program counter, stack pointer, index registers, instruction register, etc.
The CPU of a small computer is a microprocessor. Fig . show the schematic diagram of a microcomputer. The CPU of a large computer contains a number of microprocessor and other ICs on one or more circuit boards. Each microprocessor in a large CPU performs a specific task.
Fig. shows the schematic diagram of a CPU or microprocessor. The major sections of a CPU are:
(1) Arithmetic and Logic Unit (ALU)
The function of a ALU is to perform arithmetic and logic operations such as addition, subtraction, multiplication and division; AND, OR, NOT (complement) and EXECLUSIVE OR operations. It also perform increment, decrement, shift and clear operations.
| ALU | ACCUMULATOR |
| GENERAL & SPECIAL | |
| TIMING AND | |
(2) Timing and Control Unit
The timing and control unit generates timing and control signals necessary for the execution of instructions. It provides status, control and timing signals necessary for the operation of other parts of the CPU, memory and I/O devices. It controls the entire operation of a computer. It is actually the control section of the CPU, which acts as the brain of a computer.
(3) Accumulator, General and Special Purpose Registers
The accumulator is a register which holds one of the operands prior to the execution of an instruction and receives result of the most arithmetic and logical operations. It is the most frequently used register. Some CPUs contain a single accumulator, other contain several accumulators. General purpose registers store data and intermediate results during the execution of a program. They are accessible to programmers through instructions if they are working in an assembly language. Special purpose registers are not accessible to users. They are used by the computer for different purpose during program execution. Examples of special purpose registers are: program counter, stack pointer, index registers, instruction register, etc.
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