Program counter (PC)
Beginner
A small counter in the chip that remembers where in the program it is, like a bookmark.
Novice
The register that holds the memory address of the instruction being fetched. It normally moves on to the next instruction (4 bytes further for a 32-bit instruction); a branch or jump loads a new address instead.
Expert
Architectural state; in a pipeline the fetch PC runs ahead of the instructions in flight, and every stage carries its own instruction’s PC for branch targets and precise exceptions.
Explained in Instructions and pipelines (Architectures).
See also: Instruction set architecture (ISA).