Machine Language Program

There are at least two sensible programs for the toothbrush. The table shows one of them.

In the electronic memory of the toothbrush the program is stored as a sequence of bytes:

0000 0001 
0000 0010 
0000 1000 
0000 0100 
0000 0000 

The processor starts at the beginning and performs the action described by that code and continues through the bytes in sequence until it reaches the one (at address 3) that says to start over. If the switch is moved to the "off" position, the processor skips that instruction and instead performs the "stop" instruction at address 4.

This is, of course, a silly example. Electric toothbrushes are not controlled by computer processors. And, the machine instructions of actual processors are much more detailed. But the essential ideas of the example are these:

• A machine language program is a sequence of machine language instructions in main memory.
• A machine instruction consists of one or more bytes (in this example, only one).
• The processor runs a program one machine instruction at a time.
• All the little machine operations add up to something useful.

If toothbrush user leaves the switch "on" for a while, the program repeats its operations many times. This is how most programs in real computers run — many little operations add up to a useful function, which is then repeated many times.