Programs share some attributes with essays. For essays, the most important question readers ask is, "What is it about?" For programs, the main question is, "What does it do?" In fact, the purpose should be sufficiently clear that neither question ever needs to be uttered. Still, for both essays and computer code, it's always important to look at how each one is written. Even if the idea itself is good, it will be difficult to transmit to the desired audience if it is difficult to understand. The style in which they are written is just as important as their purpose. Both essays and lines of code are meant—before all else—to be read and understood by human beings.
You may ask: "Are human beings actually supposed to be the ones reading computer programs?" The assumption is that people use programs to tell computers what to do, and computers then use compilers or interpreters to compile and understand the code. At the end of the process, the program is translated into machine language that is normally read only by the CPU. That is, of course, the way things work, but this explanation only describes one aspect of computer programs.
Most programs are not write-once. They are reworked and rewritten again and again in their lives. Bugs must be debugged. Changing requirements and the need for increased functionality mean the program itself may be modified on an ongoing basis. During this process, human beings must be able to read ...