When a program is running, it’s instructions are held in storage location in the memory. The processor starts with the first instruction and repeats the following stages until the program ends.
- Address of instructions are placed on the address bus
- Contents of locations (instruction’s) are transferred to a register along the data bus
- The instructions are decoded and executed
This is known as the fetch and execute cycle
Example
number=int(input(“Please enter a number”)
Address bus – holds the address in memory where the instructions are stored.
Data bus – transfers the instructions from the memory to the registers within the processor.
Control Unit – executes the instructions by requesting input, receives input value from keyboard and temporary stores value in the register.
Address Bus – holds memory location address of number variable
Data bus – transfers value from registers to memory locations
