(ANSI) C Language Functions Reference

You can select a function from the alphabetical list below or you can use the menu to navigate and select by header file to find the function you seek.

C Language Reference Tables


C Library Functions

  • abort() - Abort the current process
  • abs() - Absolute value
  • acos() - the arc cosine of x in radians
  • asctime() - Convert tm structure to string
  • asin() - the arc sine of x in radians
  • atan() - the arc tangent of x in radians
  • atan2() - the arc tangent in radians of y/x
  • atexit() - Set function that must be executed on exit
  • atof() - Convert a string to a double
  • atoi() - Convert a string to an integer
  • atol() - Convert a string to a long integer
  • bsearch() - Binary search in array
  • calloc() - Allocate space for an array in memory
  • ceil() - the smallest integer value greater than or equal to x
  • clock() - Clock ticks elapsed since the start of the program
  • cos() - the cosine of a radian angle
  • cosh() - the hyperbolic cosine
  • ctime() - Convert time_t value to string
  • difftime() - Difference between two times
  • div() - Integral division
  • exit() - Terminate calling process
  • exp() - exponential value
  • fabs() - the absolute value of x
  • floor() - the largest integer value less than or equal to x
  • fmod() - the remainder of x divided by y
  • free() - De-allocate space in memory
  • frexp() - significand and exponent
  • getenv() - Get the environment string
  • gmtime() - Convert calendar time to UTC
  • isalnum() - Alphanumeric test
  • isalpha() - Alphabetic test
  • iscntrl() - Control character test
  • isdigit() - Decimal digit test
  • isgraph() - Printing character test (Space is not included)
  • islower() - Lower case letter test
  • isprint() - Printing character test (Space included)
  • ispunct() - Printing character (except space,digit,letter)
  • isspace() - Space, tab, vtab, formfeed, newline, cr test
  • isupper() - Upper case letter test
  • isxdigit() - Hexidecimal digit test
  • labs() - Absolute value
  • ldexp() - return x multiplied by 2 raised to the power of exponent
  • ldiv() - Integral division
  • localtime() - Convert calendar time to local time
  • log() - the natural logarithm (base-e logarithm)
  • log10() - the common logarithm (base-10 logarithm)
  • malloc() - Allocate a memory block
  • mblen() - Get length of a multi-byte character
  • mbtowc() - Convert a multi-byte character to wide character
  • memchr() - Pointer to the first occurence c in the first n bytes of a memory area
  • memcmp() - Compare n characters of target with source
  • memcpy() - Copy n characters from source to target
  • memmove() - Copy n characters from source to target (even with overlap)
  • memset() - Copies x into a buffer y and does this n times.
  • mktime() - Convert the tm structure to time_t
  • modf() - break into fractional and integral
  • pow() - x raised to the power of y
  • qsort() - Sort elements of array
  • rand() - Generate random number
  • realloc() - Reallocate a memory block
  • sin() - the sine of a radian angle
  • sinh() - the hyperbolic sine
  • sqrt() - the square root
  • srand() - Initialize random number generator
  • strcat() - Concatenates one string onto the end of another string
  • strchr() - Pointer to first occurrence of x in a string
  • strcmp() - Compares two strings
  • strcpy() - Copy of a string
  • strftime() - Format date and time
  • strlen() - Length of a string
  • strncat() - Concatenates up to n characters
  • strncmp() - Compares up to n characters
  • strncpy() - Copy of a string up to n characters
  • strrchr() - Pointer to last occurrence of x in a string
  • strstr() - Pointer to first occurrence of x in a string
  • strtod() - Convert a string to a double
  • strtol() - Convert a string to a long integer
  • strtoul() - Convert a string to an unsigned long integer
  • system() - Execute system commands
  • tan() - the tangent of a radian angle
  • tanh() - the hyperbolic tangent
  • time() - Current calendar time
  • tolower() - Convert to lower case
  • toupper() - Convert to upper case