Pocket - 15-213/15-513 Intro to Computer Systems: Code Style

URL: https://getpocket.com/read/225087580

Good code should be mostly self-documenting: your variable names and function calls should generally make it clear what you are doing. Comments should not describe what the code does, but why; what the code does should be self-evident. (Assume the reader knows C better than you do when you consider what is self-evident.)

Why not what

File header: Each file should contain a comment describing the purpose of the file and how it fits in to the larger project. This is also a good place to put your name and email address.

Purpose

Large blocks of code: If a block of code is particularly long, a comment at the top can help the reader know what to expect as they’re reading it, and let them skip it if it’s not relevant.

long code

Function header: Each function should be prefaced with a comment describing the purpose of the function (in a sentence or two), the function’s arguments and return value, any error cases that are relevant to the caller, any pertinent side effects, and any assumptions that the function makes.

argument, return value, error handling, assumptions

Tricky bits of code: If there’s no way to make a bit of code self-evident, then it is acceptable to describe what it does with a comment. In particular, pointer arithmetic is something that often deserves a clarifying comment.

tricky hack

You should use#define to clarify the meaning of magic numbers. In the above example, doing “#define BUFLEN 256” and then using the “BUFLEN” constant in both the declaration of “buf” and the call to “fgets”.

magic number use define

If you allocate memory (malloc, calloc), you should free it after use. Your program should not have memory leaks. If you use open a file, you should close it after use. Closing a file is very important, especially with output files. The reason is that output is often buffered.

Close file