There is a vast collections of function .Some of them are grouped together and listed below.
String Function:
strcpy: -copies one string into another.
strcat :-appends one string to another.
strcmp: -compare one string to another.
strcmpi: -compare one string to another without case sensitive.
strlen :-calculates the length of a string.
strrev :-reserve a string.
Mathematical Function:
abs: -returns absolute value of an integer.
sin :-calculate the sine.
cos: -calculate the arc cos.
tan :-calculate the arc tangent.
acos :-calculate the arc cosine.
asin :-calculate the arc sine.
atan :-calculate the arc tangent.
ceil :-rounds up.
floor :-rounds down.
log :-calculate the natural logarithm of x.
pow :-calculate x to the power of y.
sqrt :-calculate the positive square root of input value.
Date & Time Function:
asctime() :-converts date and time to ASCII.
clock() :-determine process time.
getdate() :-gets system date
gettime() :-gets system time.
setdate(): -sets DOS date
settime ():-sets system time.
time ():-gets time of day.
Utility Function:
abort() :-abnormally terminates a process.
bsearch()- binary search of an array.
tolower(): -translate character to lower case.
toupper()- translate character to upper case.
qsort() :-sorting using the quick sort algorithm.
exit() :-terminate execution of a program.
free() :frees allocated block.
Character Class Test Functions:
isupper() :-check and returns non-zero if c is an upper case letter (A-Z).
islower() :-check and returns non-zero if c is a lower case letter (a-z).
isspace(() :-check and returns non-zero if c is a space tab, carriage return, newline, vertical tab, form feed etc.
isascii() :-tests whether a character is an ASCII (0 to 127) character.
isalpha() :-check and returns non-zero if c is a letter (A-Z or a-z).
iscntrl() :-tests whether a character is a control character.
toascii() ;-translate character to ASCII format.
tolower() :-translate character to upper case.
There Are some more artical see:
processing data file
creating data file
Opening and closing data file
File-operation
Data file handling (introduction)
Dynamic data structure link list
