Executing Instructions

The word "execute" is often used to mean "perform the machine operation that an instruction asks for." So you can say that "executing the instruction 0000 0000 stops the toothbrush," or "millions of instructions execute per second." "Execute" is also used for an entire program or part of a program: "to execute the program, turn the switch to on."

Most machine language programs are made up of instructions that are executed again and again. In the toothbrush program there was an instruction that caused the processor to start the program again from the beginning. In a real computer, millions of instructions execute per second, so something like this is necessary if the 32 megabytes of a typical computer are to hold a program that runs for more than a few seconds.

A group of machine instructions that can be repeatedly executed is called a loop.

A typical processor is made up of several million transistors, all on one small wafer of silicon called an integrated circuit (also called a chip.) The toothbrush processor could probably be built with just a few hundered transistors. Integrated circuits are used for other electronic parts of a computer: for example main memory is implemented with memory chips.