C's efficiency is granted in part by its stripped-down appearance. At the same time, C is made extremely powerful and flexible by the addition of STANDARD FUNCTION LIBRARIES for input/output, mathematics, string manipulation, and memory management. Programs making use solely of these functions are generally portable (or can be made so with judicious use of conditional compilation*). In Think C 4.0 the ANSI library contains all these standard functions. (Previous versions had separate stdio, math, strings, and storage libraries.)
In addition, many C compilers provide specialized function libraries appropriate to the intended hardware or application area. These further enhance the language's power while compromising portability. In TC, the non-standard 'console' library provides the ccommand() function used to simulate UNIX-style command-line processing. TC's MacTraps library actually consists of calls to the Macintosh ROM "Toolbox" routines which accomplish the graphical user interface. This "library" allows TC programmers to call these routines as though they were C functions. (These functions are declared automatically in the "precompiled header" MacHeaders.)
Programmers may also create their own libraries of related, frequently-used routines.
