Advantages of Functions:

There are many advantages in using functions:

  • It makes possible top down modular programming. In this style of programming, the high level logic of the overall problem is solved first while the details of each lower level functions is addressed later.
  • The length of the source program can be reduced by using functions at appropriate places.
  • It becomes uncomplicated to locate and separate a faulty function for further study.
  • A function may be used later by many other programs this means that a c programmer can use function written by others.
  • A function can be used to keep away from rewriting the same block of codes which we are going use two or more locations in a program. This is especially useful if the code involved is long or complicated.

All C Functions

# and ##

manipulate strings

#define

define variables

#error

display an error message

#if, #ifdef, #ifndef, #else, #elif, #endif

conditional operators

#include

insert the contents of another file

#line

set line and file information

#pragma

implementation specific command

#undef

used to undefine variables

Predefined preprocessor variables

miscellaneous preprocessor variables

abort

stops the program

abs

absolute value

acos

arc cosine

asctime

a textual version of the time

asin

arc sine

assert

stops the program if an expression isn't true

atan2

arc tangent, using signs to determine quadrants

atexit

sets a function to be called when the program exits

atof

converts a string to a double

atoi

converts a string to an integer

atol

converts a string to a long

bsearch

perform a binary search

calloc

allocates and clears a chunk of memory

ceil

the smallest integer not less than a certain value

clearerr

clears errors

clock

returns the amount of time that the program has been running

cos

cosine

cosh

hyperbolic cosine

ctime

returns a specifically formatted version of the time

difftime

the difference between two times

div

returns the quotient and remainder of a division

exit

stop the program

exp

returns ā€œeā€ raised to a given power

fabs

absolute value for floating-point numbers

fclose

close a file

feof

true if at the end-of-file

ferror

checks for a file error

fflush

writes the contents of the output buffer

fgetc

get a character from a stream

fgetpos

get the file position indicator

fgets

get a string of characters from a stream

floor

returns the largest integer not greater than a given value

fmod

returns the remainder of a division

fopen

open a file

fprintf

print formatted output to a file

fputc

write a character to a file

fputs

write a string to a file

fread

read from a file

free

returns previously allocated memory to the operating system

freopen

open an existing stream with a different name

frexp

decomposes a number into scientific notation

fscanf

read formatted input from a file

fseek

move to a specific location in a file

fsetpos

move to a specific location in a file

ftell

returns the current file position indicator

fwrite

write to a file

getc

read a character from a file

getchar

read a character from STDIN

getenv

get enviornment information about a variable

gets

read a string from STDIN

gmtime

returns a pointer to the current Greenwich Mean Time

isalnum

true if a character is alphanumeric

isalpha

true if a character is alphabetic

iscntrl

true if a character is a control character

isdigit

true if a character is a digit

isgraph

true if a character is a graphical character

islower

true if a character is lowercase

isprint

true if a character is a printing character

ispunct

true if a character is punctuation

isspace

true if a character is a space character

isupper

true if a character is an uppercase character

isxdigit

true if a character is a hexidecimal character

labs

absolute value for long integers

ldexp

computes a number in scientific notation

ldiv

returns the quotient and remainder of a division, in long integer form

localtime

returns a pointer to the current time

log

natural logarithm

log10

natural logarithm, in base 10

longjmp

start execution at a certain point in the program

malloc

allocates memory

memchr

searches an array for the first occurance of a character

memcmp

compares two buffers

memcpy

copies one buffer to another

memmove

moves one buffer to another

memset

fills a buffer with a character

mktime

returns the calendar version of a given time

modf

decomposes a number into integer and fractional parts

perror

displays a string version of the current error to STDERR

pow

returns a given number raised to another number

printf

write formatted output to STDOUT

putc

write a character to a stream

putchar

write a character to STDOUT

putenv

add/modify the environmental settings

puts

write a string to STDOUT

qsort

perform a quicksort

raise

send a signal to the program

rand

returns a pseudorandom number

realloc

changes the size of previously allocated memory

remove

erase a file

rename

rename a file

rewind

move the file position indicator to the beginning of a file

scanf

read formatted input from STDIN

setbuf

set the buffer for a specific stream

setjmp

set execution to start at a certain point

setlocale

sets the current locale

setvbuf

set the buffer and size for a specific stream

signal

register a function as a signal handler

sin

sine

sinh

hyperbolic sine

sprintf

write formatted output to a buffer

sqrt

square root

srand

initialize the random number generator

sscanf

read formatted input from a buffer

strcat

concatenates two strings

strchr

finds the first occurance of a character in a string

strcmp

compares two strings

strcoll

compares two strings in accordance to the current locale

strcpy

copies one string to another

strcspn

searches one string for any characters in another

strerror

returns a text version of a given error code

strftime

returns individual elements of the date and time

strlen

returns the length of a given string

strncat

concatenates a certain amount of characters of two strings

strncmp

compares a certain amount of characters of two strings

strncpy

copies a certain amount of characters from one string to another

strpbrk

finds the first location of any character in one string, in another string

strrchr

finds the last occurance of a character in a string

strspn

returns the length of a substring of characters of a string

strstr

finds the first occurance of a substring of characters

strtod

converts a string to a double

strtok

finds the next token in a string

strtol

converts a string to a long

strtoul

converts a string to an unsigned long

strxfrm

converts a substring so that it can be used by string comparison functions

system

perform a system call

tan

tangent

tanh

hyperbolic tangent

time

returns the current calendar time of the system

tmpfile

return a pointer to a temporary file

tmpnam

return a unique filename

tolower

converts a character to lowercase

toupper

converts a character to uppercase

ungetc

puts a character back into a stream

va_arg

use variable length parameter lists

vprintf, vfprintf, and vsprintf

write formatted output with variable argument lists

vscanf, vfscanf, vsscanf

gets formatted input from stdin with variable argument lists


The reference site for this content is http://www.cppreference.com/wiki/c/all

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