This is, of course, a silly example. Actual processors have many more machine instructions and the instructions are much more detailed. A typical processor has a thousand or more different machine instructions. Those instructions do not directly affect any output device (such as our light bulb.)

Even the simplest controller has much more memory.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.

In days long ago, the ones and zeros of a machine language program were entered into main memory by flipping switches on the front panel of a computer. The on-or-off state of each bit was displayed by lights. You may have seen this in old science fiction movies. These days there are more convenient ways to put ones and zeros into main memory. But the idea is still the same: machine instructions are patterns of ones and zeros, and data are patterns of ones and zeros.