Chapter 19. Principles: Connecting to You

Chapter 1, "Computers," noted that programmability is one of the defining features of a computer. But you need some way of getting a program into your computer. After all, the program is how you take command and control your computer.

Engineers programmed the first computers with wires and plug- boards . The wiring defined patterns that formed the digital code of the program. Although such hard-wired programs are the ultimate in nonvolatile memory, they are a bit inconvenient. Each bit in a program is a connection you have to make by hand, and all too often you're apt to make a few mistakes as you plug in thousands of wires.

Next, engineers tried banks of switches to enter programs. Although switches are a bit easier to change than hard wiring, they are just as prone to error, and it's time consuming to have to enter each bit, one at a time.