Smaller C

Chapter 4. Bits and (Many) Bytes

Before we start building more complex programs with things like functions in Chapter 5, we should cover two more useful storage categories in C: arrays and individual bits. These aren’t really distinct types like int or double, but they are useful when dealing with tiny things or with lots of things. Indeed, the notion of an array, a sequential list of items, is so useful we had to cheat back in “Getting User Input” and use it without much explanation to store user input in the form of a string.

We have also discussed the idea of Boolean values that are either yes or no, true or false, 1 or 0. When dealing with microcontrollers in particular, you will regularly have a small collection of sensors or switches that are providing on/off values. C’s normal storage options would mean devoting an entire char (8 bits) or int (16 bits) to keeping track of such tiny values. That feels like a bit (ha!) of a waste, and it is. C has a few tricks you can employ to store this type of information more efficiently. In this chapter, we’ll tackle both the big stuff by declaring arrays and then accessing and manipulating their contents, as well as how to work with the smallest bits (ahem). (And I promise not to make more bit puns. Mostly.)

Storing Multiple Things with Arrays

It is almost impossible to find a C program tackling real-world problems that does not use arrays. If you have to work with any collection of values of any type at all, those values will almost ...