Книга: Introduction to Microprocessors and Microcontrollers

How the microprocessor handles numbers (and letters)

In the last chapter, we saw how numbers could be represented in binary and hex forms. Whether we think of a number as hex or binary or indeed denary, inside the microprocessor it is only binary. The whole concept of hex is just to make life easier for us.

We may sit at a keyboard and enter a hex (or denary) number but the first job of any microprocessor-based system is to convert it to binary. All the arithmetic is done in binary and its last job is to convert it back to hex (or denary) just to keep us smiling.

There was a time when we had to enter binary and get raw binary answers but thankfully, those times have gone. Everything was definitely NOT better in the ‘good old days’.

The form binary numbers take inside of the microprocessor depends on the system design and the work of the software programmers. We will take a look at the alternatives, starting with negative numbers.

In real life, it is easy, we just put a – symbol in front of the number and it is negative so +4 becomes –4. Easy, but we don’t have any way of putting a minus sign inside the microprocessor. We have tried several ways round the problem.

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