c libc naming

What does “f” stand for in C standard library function names?

What does f stand for in the name of C standard library functions? I have noticed that a lot of functions have an f in their name, and this does not really make sense to me.

For example: fgets, fopen, printf, scanf, sqrtf and so on.

Your question in general is too general but I can explain a few examples.

  • fgets, fopen, fclose, … — The ”f“ stands for “file”. These functions accept or return a FILE * pointer as opposed to a file number as the POSIX functions do.
  • printf, scanf, … — The ”f“ stands for “formatted”. These functions accept a format string.
  • fprintf, fscanf — This is a combination of the above two.
  • sinf, cosf, … — The “f” stands for float (to distinguish from the double alternatives). Note that this fits quite nicely with suffixing floating point literals with an f as in 1.5f.
  • Finally, as Deduplicator points out, there are some names such as free, floor or setbuf (“set buffer”) where the “f” simply appears as a natural language character.

The tradition of pre- or suffixing names with single letters that indicate the type of the arguments is a necessity in C that has become obsolete in C++ thanks to overloading. Actually, overloading in C++ works by the compiler automatically adding those suffixes again under the hood to the generated symbols by a process called name mangling.