C Run-Time Library Reference

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RAD Studio has several hundred functions, macros, and classes that you call from within your C and C++ programs to perform a wide variety of tasks, including low- and high-level I/O, string and file manipulation, memory allocation, process control, data conversion, mathematical calculations, and more.

This topic refers to Windows C/C++ RTL.

For macOS C/C++ RTL, see MacOS C RTL. For iOS C/C++ RTL, see iOS C RTL.

Note: In the online help, each function, macro, and class in the C Run-time Library is listed only once. However, some functions, macros, and classes are defined in more than one header file. For example, _strerror is defined in both string.h and stdio.h. For functions that are defined in several header files, the online help assigns the function to the first header file in alphabetic order. Thus, you will find _strerror listed in the help in stdio.h but not in string.h.


Header Files

The following header files are located in $(BDS)\include\windows\crtl.

Only the most commonly used header files are documented.

For information about standard headers, see the following external resources:

For information about Dinkumware headers, see:

  • Dinkum C++ Library Reference in local help (with Dinkumware enabled in the Filtered by field)

You can also open any header file on your system and see the comments inside.


In parentheses are indicated the C++ headers:



  • bitset.h
  • deque.h
  • fstream.h
  • function.h
  • iomanip.h
  • ios.h
  • iosfwd.h
  • iostream.h
  • istream.h
  • iterator.h
  • locale.h
  • new.h
  • numeric.h
  • memory.h
  • ostream.h
  • set.h
  • stack.h
  • stdexcept.h
  • streambu.h
  • strstrea.h
  • valarray.h
  • vector.h
  • typeinfo.h


  • hash_map.h
  • hash_set.h
  • queue.h
  • list.h
  • rope.h
  • slist.h
  • utility.h


Perl compatible regular expressions

Warning: Perl-compatible regular expression headers are deprecated, and they are not available for all C++Builder compilers. Use regex from the C++ standard library instead.
  • pcre.h
  • pcreposi.h
  • pcreposix.h

See Also