The Processor The Main Components Arithmetic/Logic Unit (ALU) Control Unit System Clock Registers

Arithmetic/Logic Unit (ALU) This is where all the arithmetic and logic operations are carried out on data. System Clock

Arithmetic/Logic Unit (ALU) Arithmetic operations such as addition, subtraction, multiplication and division. Logical operations consist of comparing one data item with another to determine whether or not the first data item is smaller than, equal to or greater than the second data item. Do you remember what these operators do?

System Clock Generates a continuous sequence of clock pulses to step the control unit through its operations. System Clock

Registers Special storage locations called registers are included in this circuitry to hold information temporarily whilst it is being decoded and manipulated.

Control Unit Coordinates all the activities taking place in the CPU, memory and peripherals, by sending control signals to the various devices. System Clock

Control Unit cont… The Control Unit coordinates and controls all the operations carried out by the computer. It operates by repeating three operations: Fetch – causes the next instruction to be fetched from the main memory. Decode – translates the program instruction into commands that the computer can process. Execute – causes the instruction to be executed.

1. The Processor 1. The Processor asks the memory for each instruction in turn. 1. The Instruction Pointer keeps track which memory location contains the next program instruction. System Clock

2. E ach instruction is placed in turn on the bus by the memory… 2. …and The Processor takes these instructions. System Clock

3. The Instruction Decoder 3. The Instruction Decoder interprets the meaning of each of the instructions (in turn). 3. System Clock

4. The Instructions, (in turn), are a request for the numbers from the two memory locations. 4. The instructions are interpreted by the Instruction Decoder each time. System Clock

5. The Value, in 5070, which is 76, is placed in the processor’s register Ax, (internal storage area). 5. The processor takes the value in 5072, which is 50, and places it in the Register Bx. Ax Bx

System Clock 6. The next instruction states that the two values should be added together. 6. The Arithmetic/ Logic Unit carries out the addition. Ax Bx

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

6. This instruction adds each pair of digits in turn by use of a series of adders. The results are placed into register Ax

…another instruction tells the processor to put the numbers back into the memory. 7. …another instruction tells the processor to put the numbers back into the memory. 7. Ax Bx System Clock

The Processor Main components: Arithmetic/Logic Unit (ALU) Control Unit System Clock Registers