There are many built-in functions in C++ which can be used by a programmer as needed. To allow a build-in function or usage of some pre-fixed declarations C++ provides a concept of header files. Header file primarily contains the function prototypes of built-in functions so that its type checking can be performed and related library can be linked in the compilation and linking process. Some popular functions are listed below. (This is not a comprehensive list, it has been provided for the purpose of reference to clear many +2 and graduate level examinations). Detailed documentation can be referred by clicking over the header filename. The names of header files shown in round brackets below are the versions which are supported on modern IDEs and are required for unicode support. For e.g. we need to use cstring in place of string.h for unicode support.
iostream.h (iostream) input output stream functions
open, close, get, getline, read, write, put, seekg, seekp, tellg, tellp, ignore, flush, eof, bad, fail, good, clear
stdlib.h (cstdlib) general purpose functions
atof, atoi, atol, strtod, strtol, strtoul, rand, srand, calloc, free, malloc, realloc, abort, atexit, exit, getenv, system, bsearch, qsort, abs, div, labs, ldiv
macro: NULL, RAND_MAX, EXIT_FAILURE, EXIT_SUCCESS
Types: div_t, ldiv_t, size_t
string.h (cstring) manipulate cstring and character arrays
strlen, strcpy, strncpy, strcat, strncat, strcmp, strncmp, strchr, strcspn, strpbrk, strrchr, strspn, strstr, strtok, strerror, memcpy, memcmp, memmove, memset, memchr,
Macros: NULL, Variables: size_t
ctype.h (cctype) classify and transform individual characters
isalnum, isalpha, isblank, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit, tolower, toupper
stdio.h (cstdio) handle streams from devices
fgetc, fgets, fputc, fputs, getc, getchar, gets, putc, putchar, puts, ungetc, fclose, fflush, fopen, freopen, fread, fwrite, setbuf, setvbuf, fread, fwrite, fgetpos, fseek, fsetpos, ftell, rewind, remove, rename, feof, clearerr, ferror, perror, fprintf, fscanf, printf, scanf, sprintf, sscanf, vfprintf, vprintf, vsprintf
Macros: EOF, BUFSIZE, FILENAME_MAX, FOPEN_MAX, NULL
Types: FILE, fpos_t, size_t
math.h (cmath) common math operations and transformations
cos, sin, tan, acos, asin, atan, atan2, cosh, sinh, tanh, exp, frexp, ldexp, log, log10, modf, pow, sqrt, ceil, floor, fmod, fabs, abs
Macros: NAN
Types: float_t
iomanip.h (iomanip) providing parametric manipulators
setiosflags, resetiosflags, setbase, setfill, setprecision, setw, get_time, put_time
There are many other header files which are used in c++ prorgamming for e.g. –
assert.h, errno.h, float.h, limits.h, setjmp.h, signal.h, stdargs.h, stdbool.h, stddef.h, stdint.h, tgmath.h, time.h, wchar.h, wctype.h
Most of the above are used for advanced needs and professional programming. A complete reference can be seen here
