"Complex Instruction Set Computing" is what CISC stands for. The built-in instruction set of CISC processors contains a sizable number of computer commands. Simple chores and multi-step procedures can both be lengthy CISC commands, with the latter requiring multiple clock cycles. Along with Reduced Instruction Set Computing, CISC is one of the two main design theories used in instruction set architecture (RISC). The most common kind of CISC CPU is one with the x86 processing design, which is used in both Intel and AMD processors.

In a CISC instruction set, a single command may carry out several different tasks. For instance, it may order the CPU to import numbers from two memory regions, multiply them, and then store the output. Fewer lines of assembly code, which in turn require less RAM to hold instructions, are produced by a software assembler when complicated instructions are integrated directly into the processor's instruction set.

CISC and RISC

There are two distinct approaches to instruction set design: CISC and RISC. When compared to the other, each has benefits and disadvantages of its own.

In contrast to RISC instruction sets, which have fewer instructions that each require one clock cycle, CISC instruction sets have more instructions that can perform more complex jobs over a number of clock cycles. The quantity of clock cycles needed is frequently the same when a sequence of RISC instructions performs the same job as a single CISC command.

Additionally, CISC computers require more transistors than RISC processors to hold the bigger instruction sets. Instead of using those transistors for processing data, RISC computers can use them for memory storage. They can also use fewer transistors to create less complicated chips that can be smaller, use less energy, and generate less heat.