Like variables, function names should speak for themselves. The above arguments for naming variables apply also to functions. Instead of _, use mixed uppercase and lowercase.

It is also helpful to distinguish between global and local functions. Local functions should start with a lowercase letter, while global functions should start with an uppercase letter.

Do

    // this is a local function
    writeStringToFile (a_string, file_name);

    // this is a global function
    global_settings = ReadGlobalSettings ();

Don't

    f1 (a_string, file_name);
    gs = rgs();