by Dinesh Thakur

ClSC (pronounced "sisk") stands for complex instruction set computing. A CISC chip is a microprocessor that has a large set of instructions that are built into its microcode so it can carry out most computations directly. Compare CISC chips with RISC chips, which recognize fewer instructions. CISC term applied to all the older computer ARCHITECTURES to distinguish them from the new RISC designs introduced in the 1990s. RISC (reduced instruction set computing) technology is touted as faster than CISC and is increasingly common, although there is a great deal of debate over the pros and cons of each type of architecture.

A CISC INSTRUCTION SET contains instructions that perform several steps in one, and therefore take many CYCLES to execute - such as the Intel 8086's ADC instruction, which takes more than 20 cycles to add the contents of a REGISTER to a memory location. The concept grew through the early days of computing from a desire to make life easier for MACHINE CODE programmers, but now that most programming is done in HIGH-LEVEL languages it is less necessary and hinders hardware efficiency. RISC designs employ a larger number of simple, one cycle operations that are automatically generated by a COMPILER.