The stored program concept revision notes

Core idea

The stored program concept is the arrangement in which machine code instructions are stored in main memory. The processor obtains these instructions from main memory and processes them.

Fetching and execution

The processor fetches a machine code instruction from main memory and then executes it. Execution means carrying out the operation specified by the instruction. The processor performs these actions serially, meaning that the instructions are dealt with in sequence rather than all being executed at the same time.

A simple abstract sequence might be:

1. A machine code instruction representing an arithmetic operation is stored in main memory.
2. The processor fetches that instruction.
3. The processor executes the arithmetic operation.
4. The processor then fetches the next instruction in the sequence.
5. The next instruction is executed, and the process continues serially.

The operations performed by the processor include arithmetic operations, such as calculations, and logical operations, such as operations involving logical reasoning or comparison. The stored program concept therefore links the storage of instructions in main memory with their sequential processing by the processor.

Important distinction

The instructions are not merely stored as information for reference. They are machine code instructions that the processor fetches and executes. The concept specifically concerns the relationship between main memory, the processor, and the serial execution of instructions.

Common errors

• Saying that the instructions are stored only in the processor: the requirement states that they are stored in main memory.
• Describing the instructions as being executed simultaneously: they are fetched and executed serially.
• Mentioning only calculations: the processor performs both arithmetic and logical operations.
• Describing a program without referring to machine code instructions: the stored program concept concerns instructions in machine code stored in main memory.