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When we look at the different types of software that run on computer systems, from financial applications to graphics intensive games, it is easy to forget that computers are really just binary machines. Binary systems work in terms of 0 and 1, true or false, set and unset. All the data sitting in RAM, stored on disk drives and flowing through circuit boards and buses are nothing more than sequences of 1s and 0s. Each 1 or 0 is referred to as a ''bit'' and bits are grouped together in blocks of 8, each group being referred to as a ''byte''. When people talk about 32-bit and 64-bit computer systems they are talking about the number of bits that can be handled simultaneously by the CPU bus. A 64-bit CPU, for example, is able to handle data in 64-bit blocks, resulting in faster performance than a 32-bit based system.

Data types are the basic building blocks of just about every programming language and Objective-C is no exception. Now that we have covered these basics we will move on to the next chapter and begin talking about the use of variables.

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