Introduction to C language function

Classification function, where the function library is ctype.h

int isalpha (int ch) If CH is a letter (' A '-' Z ', ' a '-' Z ') returns a value other than 0, otherwise returns 0

int isalnum (int ch) returns 0 if CH is a letter (' A '-' Z ', ' a '-' z ') or a number (' 0 '-' 9 ') returns a value other than 0

int isascii (int ch) If Ch is a character (0-127 in ASCII) returns a value other than 0, otherwise it returns 0

int Iscntrl (int ch) If CH is a voided character (0x7F) or a normal control character (0x00-0x1f) returns a value other than 0, otherwise returns 0

int isdigit (int ch) If CH is a number (' 0 '-' 9 ') returns a value other than 0, otherwise returns 0

int isgraph (int ch) If CH is a printable character (excluding spaces) (0x21-0x7e) returns a value other than 0, or 0

int islower (int ch) returns a value other than 0 if CH is a lowercase letter (' A '-' z '), or 0

int isprint (int ch) If CH is a printable character (with spaces) (0x20-0x7e) returns a value other than 0, otherwise returns 0

int ispunct (int ch) If Ch is a punctuation character (0x00-0x1f) returns a value other than 0, otherwise returns 0

int isspace (int ch) If CH is a space ("), horizontal tab (' \ t '), carriage return (' \ R '), paper wrap (' \f '), Vertical tab (' \v '), line feed (' \ n ') returns a value other than 0, or 0.

int isupper (int ch) If CH is uppercase (' A '-' Z ') returns a value other than 0, otherwise returns 0

int isxdigit (int ch) If CH is a 16 number (' 0 '-' 9 ', ' a '-' f ', ' a '-' F ') returns a non-0 value, otherwise returns 0

int tolower (int ch) If CH is uppercase (' a '-' Z ') returns the corresponding lowercase letter (' A '-' Z ')

int toupper (int ch) returns the corresponding capital letter (' a '-' z ') if CH is a lowercase letter (' A '-' Z ')

Mathematical functions, where the function library is math.h, stdlib.h, String.h, float.h

int abs (int i) returns the absolute value of integral parameter I

Double cabs (struct complex znum) returns the absolute value of the plural znum

Double fabs (double x) returns the absolute value of the double precision parameter x

Long Labs (long N) returns the absolute value of an integer parameter n

Double exp (double x) returns the value of the exponent function ex

Double Frexp (double value,int *eptr) returns the value of x in Value=x*2n, and N is stored in eptr

Double Ldexp (double value,int exp); Returns the value of the Value*2exp

Double log (double x) returns the value of the Logex

Double log10 (double x) returns the value of log10x

Double pow (double x,double y) returns the value of XY