The document summarizes common C functions for character, string, and mathematical operations. It lists functions from the ctype.h, string.h, and math.h header files that check character properties, manipulate strings, and perform basic math.

1. CHARACTER FUNCTIONS Header file: ctype.h int isalpha (int ch): returns non zero if ch is alphabet else returns 0 int isalnum (int ch): returns non zero if ch is alphabet or digit else returns 0 int isdigit (int ch): returns non zero if ch is a digit ( 0 – 9) else returns 0 int islower (int ch): returns non zero id ch is a lower case letter else returns 0.

2. int isupper ( int ch ): returns non zero if ch is in uppercase letter else 0. int toupper ( int ch ): returns uppercase equivalent of ch if ch is a letter otherwise ch is returned unchanged. int tolower ( int ch): returns lowercase equivalent of ch if ch is a letter else ch is returned unchanged.

3. STRING FUNCTIONS HEADER FILE : string.h int strlen ( str ) returns the length of the string int strcmp ( str1, str2 ) & int stricmp (str1, str2) returns 0 id str1 = str2 >0 if str1 > str2 <0 if str1 < str2 Note : stricmp ignores case of the character char strcpy ( dstr, sstr) copies contents of sstr to dstr int strcat ( str1, str2 ) copies contents of str2 to str1 without overwriting

4. MATHEMATICAL FUNCTIONS header file: math.h fabs (num) returns absolute value of floating point num. e.g. fabs( 1.0 ) : 1.0 fabs ( - 1.0 ) : 1.0 fmod ( x, y ) returns remainder of division x/y e.g. fmod(10.0, 4.0 ) : 2.0 log10 (num) returns base 10 logarithm for the num e.g. log10( 1.0 ) gives base 10 logarithm for 1.0. pow (x, n) returns the power of no. x to the power n.e.g. pow(4.0, 2.0) : 16 sqrt (num) returns the square root of a no. e.g. sqrt(18): 9.0

5. sin (num): returns the sine value of the no. cos (num): returns the cosine value of the number abs (num): returns the absolute value of an integer.