Base CS from zero
The processor: free-recall review
Retrieval beats re-reading. For each prompt, say or write a full answer from memory before you open the model answer — the effort of pulling the mechanism out of your head is what makes it stick.
Reconstruct the unit’s core mechanisms from memory: what an instruction is, how the fetch-decode-execute loop runs, what the program counter and registers do, and why a program is just bytes in memory.
- 01What is a CPU instruction, and what two parts does almost every instruction have?
- 02Describe the fetch-decode-execute cycle and the role of the program counter in it.
- 03Why does the CPU keep working values in registers rather than reading and writing main memory for every step?
- 04What is the difference between a general-purpose register and a special-purpose register? Give an example of each.
- 05State the stored-program (von Neumann) principle and explain why it matters in practice.
- 06What is machine code, and what is an instruction set (ISA)? Why can't an ARM binary run directly on an x86-64 chip?
If you could reconstruct each answer from memory, you hold the unit’s spine: an instruction is an operation plus operands; the CPU runs them in the fetch-decode-execute loop driven by the program counter; registers hold the working values because they are 100-300x faster than RAM; some registers (PC, stack pointer, flags, instruction register) have fixed hardware roles; and the whole program is just machine-code bytes in shared memory — the stored-program idea — which is why a single machine can run any program and why each ISA defines which bytes a given chip can run.