System Unit

Editor's Notes

1. In computing, an arithmetic logic unit (ALU) is a digital circuit that performs arithmetic and logical operations. The ALU is a fundamental building block of the central processing unit (CPU) of a computer, and even the simplest microprocessors contain one for purposes such as maintaining timers. The processors found inside modern CPUs and graphics processing units (GPUs) have inside them very powerful and very complex ALUs; a single component may contain a number of ALUs.
2. The shortest interval in which an elementary operation can take place within the processor. It is made up of some number of clock cycles. The computer can only do one thing at a time. Each action must be broken down into the most basic steps. One round of steps from getting an instruction back to getting the next instruction is called the Machine Cycle. An instruction cycle (also called fetch-and-execute cycle, fetch-decode-execute cycle, and FDX) is the time period during which a computer reads and processes a machine language instruction from its memory or the sequence of actions that the central processing unit (CPU) performs to execute each machine code instruction in a program. The name fetch-and-execute cycle is commonly used. The instruction must be fetched from main memory, and then executed by the CPU. This is fundamentally how a computer operates, with its CPU reading and executing a series of instructions written in its machine language. From this arise all functions of a computer familiar from the user's end.