Silence on the Wire

From Electronic Egg Timer to Computer

The true value of a computer lies in its ability to be programmed to act in a specific way—to execute a sequence of software commands according to some plan.

Figure 2-4 illustrates the next step on our way toward developing a flexible machine that can do more than just a single, hard-wired task: data storage and memory. In this figure, we see a type of memory storage unit known as a flip-flop design. This memory cell has two control lines, “set” and “reset.” When both are down, the gate maintains its current state, thanks to a feedback connection between its input and output to the OR gate. Previous output from OR is passed through an AND gate because its other line is set to 1 (negated “reset”), and through ...