The big idea
A computer is a team. The CPU (central processing unit) is the decision-maker that runs instructions one after another. Memory holds the instructions and data it needs. The GPU (graphics processing unit) is a specialist that handles huge piles of repetitive maths. Knowing who does what explains why some computers feel fast and others feel slow.
Explained simply
Inside the CPU:
- The control unit (CU) reads each instruction and coordinates everything else.
- The arithmetic logic unit (ALU) does calculations and comparisons.
- Registers are tiny, ultra-fast storage slots. The program counter holds the address of the next instruction, the MAR (memory address register) holds the address being accessed, and the MDR (memory data register) holds the data moving to or from memory.
The CPU repeats the fetch–decode–execute cycle: fetch the next instruction from memory, decode what it means, execute it, and repeat — billions of times a second.