Computers use main memory (RAM).
Describe the role of main memory (RAM) in the von Neumann stored program concept.
Mark scheme
Award up to two marks for a linked description such as:
- Holds/stores the data and instructions of the program currently being run (1) to be fetched by the CPU during the fetch-decode-execute cycle (1)
- Instructions and data are loaded/copied from secondary storage into RAM (1) before they can be processed by the CPU (1)
- Stores the program that is currently running (1) together with the data that it uses (1)
- Holds the data and instructions that the CPU needs next (1) so the CPU can access them quickly (1)
Allow a response that describes both that RAM holds the current program and that the program was loaded from secondary storage into RAM, provided each statement is linked to a development.
Do not accept responses about cache or registers as the store of the current program.
Do not accept responses that say RAM stores data permanently or that RAM is read-only.
Do not accept 'RAM is where the CPU processes data' (this describes the ALU/registers), or 'RAM stores the operating system' unless it is linked to the program currently being run.
Do not award a second mark for a response that only states that RAM holds data and instructions with no linked development.
Example answers and how they were marked
RAM holds the data and instructions of the program that is currently running so that the CPU can fetch them during the fetch-decode-execute cycle.
Why: Linked point (1): holds data and instructions of the current program, plus linked development (1): fetched by the CPU in the cycle.
RAM holds the data and instructions that the computer is using at the moment.
Why: States the role (1) but gives no linked development, so only the first mark is awarded.
RAM is the secondary storage, so the program is kept there when the power is switched off.
Why: Confuses main memory with secondary storage and says contents are kept without power; both near-misses are named in the 'Do not accept' lines, so no mark.