CISC is a computer architecture where the CPU supports hundreds of instructions, allowing for a wide variety of computing tasks. It improved programming efficiency by allowing higher-level languages. However, the instruction sets became more complex, leading to the introduction of RISC processors. Despite advancements, CISC processors maintain their dominance in the computing industry.
Complex Instruction Set Computing (CISC) – pronounced “sisk” – is a type of computer architecture in which the Central Processing Unit (CPU) supports hundreds of instructions. This is opposed to reduced instruction set (RISC) computers, which support fewer instructions. This means that computers that support CISC, which includes most personal computers on the market, are capable of performing a wide variety of computing tasks, making them excellent general purpose computers.
The advent of CISC computing in the 1970s and 1980s allowed computers to operate and execute complex instruction sets. This, in turn, made it possible to write denser code for these computers. In other words, less code was able to get more performance out of the computer due to the complex instruction set architecture. The instruction sets needed to operate CISC computers have become more compact, creating smaller programs and saving in both computer memory and computer storage.
Another benefit of the complex programming changes enabled by the use of the CISC computer architecture was the improvement in programming efficiency. In the early days of computing, all instructions had to be broken down into assembly language. With CISC computing, instruction sets were added to computers that allowed them to understand and process higher-level languages, which were more intuitive. This meant that programmers no longer had to break down code to make it usable.
The downside of this highly evolved computer architecture was that the instruction sets had to become more and more complex to handle the increasingly complex demands of computers. Newer operating systems allowed and encouraged parallel processing and multitasking. The more complicated operating systems and programming languages became, the more work was required of the CPU and instruction sets to decode and execute them.
One consequence of this growing complexity has been the introduction of RISC processors. These evolved from needing a computer to do a small variety of tasks, but to do them very quickly and efficiently. It didn’t take a purely business computer, for example, to have the ability to display and manipulate high-level graphics and sound required by a computer that needed to be able to play games and process spreadsheets.
Computing continued to advance and the speed and power of machines increased. This has, somewhat, blurred the line between CISC and RISC computing. However, with newer processors capable of executing multiple instructions in a stacked or pipelined fashion and handling parallelism more efficiently, CISC processors continue to maintain their dominance in the computing industry.
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