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CISC (Complex Instruction Set Computer) is a type of computer architecture where the CPU recognizes a large number of complex instructions, often designed to perform multiple low-level operations in a single step, reducing the number of instructions per program. This design leads to smaller code sizes but can result in slower execution due to complex instruction decoding and execution cycles.

How it works

Complex Instructions: A single CISC instruction can perform complex, multi-step operations, such as loading data from memory, performing an arithmetic operation, and then storing the result back to memory.

Microcode: These complex instructions are often implemented using sequences of simpler, lower-level instructions called microcode, which are stored in the CPU's microprogram control memory.

Variable-Length Instructions: CISC processors typically use variable-length instructions, which require complex logic for fetching and decoding them from memory.