2.8: Program Context

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The final bit of information to take from this chapter is that data in a computer is a series of "1" or "0" bits. In computer memory two bytes containing “01000001” could exist. The question is what does this byte mean? Is the byte an integer number corresponding to decimal 65? Is this an ASCII character, representing the letter "A"? Is it a floating point number, or maybe an address? The answer is you have no idea!

To understand data there has to be a context. HLL always provide the context with the data (for example, the type, as in int a;), so the programmer does not have to worry about it. However, in assembly the only context is the one the programmer maintains, and it is external to the program. Is it possible to convert an integer number from upper case to lower case? Or to add two operations? The answer is yes, anything is possible in assembly, but that does not mean it makes sense to do it.

In assembly language it is important for the programmer to always be aware of what a series of bits in memory represent, or the context of the data. Remember that data without a context is meaningless.