Naming Conventions

Individual projects will no doubt have their own naming conventions. There are some general rules however.

• Names with leading and trailing underscores are reserved for system purposes and should not be used for any user-created names. Most systems use them for names that the user should not have to know. If you must have your own private identifiers, begin them with a letter or two identifying the package to which they belong.
• #define constants should be in all CAPS.
• Enum constants are all CAPS
• Function, typedef, and variable names, as well as struct, union, and enum tag names should be in lower case.
• Many macro ``functions'' are in all CAPS. Some macros (such as getchar and putchar) are in lower case since they may also exist as functions. Lower-case macro names are only acceptable if the macros behave like a function call, that is, they evaluate their parameters exactly once and do not assign values to named parameters. Sometimes it is impossible to write a macro that behaves like a function even though the arguments are evaluated exactly once.
• Avoid names that differ only in case, like foo and Foo. Similarly, avoid foobar and foo_bar. The potential for confusion is considerable.
• Similarly, avoid names that look like each other. On many terminals and printers, `l', `1' and `I' look quite similar. A variable named `l' is particularly bad because it looks so much like the constant `1'.

In general, global names (including enums) should have a common prefix identifying the module that they belong with. Globals may alternatively be grouped in a global structure. Typedeffed names often have ``_t'' appended to their name.

Avoid names that might conflict with various standard library names. Some systems will include more library code than you want. Also, your program may be extended someday.

Also note the following (from [15]):

``Length is not a virtue in a name; clarity of expression is. A global variable rarely used may deserve a long name, maxphysaddr say. An array index used on every line of a loop needn't be named any more elaborately than i. Saying index or elementnumber is more to type (or calls upon your text editor) and obscures the details of the computation. When the variable names are huge, it's harder to see what's going on. This is partly a typographic issue; consider

for(i=0 to 100)
        array[i]=0

vs.

for(elementnumber=0 to 100)
        array[elementnumber]=0;

The problem gets worse fast with real examples. Indices are just notation, so treat them as such.''

``Pointers also require sensible notation. np is just as mnemonic as nodepointer if you consistently use a naming convention from which np means ``node pointer'' is easily derived.''

As in all other aspects of readable programming, consistency is important in naming. If you call one variable maxphysaddr, don't call its cousin lowestaddress.''

``Finally, I prefer minimum-length but maximum-information names, and then let the context fill in the rest. Globals, for instance, typically have little context when they are used, so their names need to be relatively evocative. Thus I say maxphysaddr (not MaximumPhysicalAddress) for a global variable, but np not NodePointer for a pointer locally defined and used. This is largely a matter of taste, but taste is relevant to clarity.

I eschew embedded capital letters in names; to my prose-oriented eyes, they are too awkward to read comfortably. They jangle like bad typography.'' ``Procedure names should reflect what they do; function names should reflect what they return. Functions are used in expressions, often in things like if's, so they need to read appropriately.

if(checksize(x))

is unhelpful because we can't deduce whether checksize returns true on error or non-error; instead

if(validsize(x))

makes the point clear and makes a future mistake in using the routine less likely.''