tolower, toupper

Converts alphabetical characters to lowercase or uppercase.

  #include <ctype.h>
  
  int tolower(int c);
  
   int toupper(int c);

Parameter

c

A character value to convert.

Remarks

The tolower() function converts an uppercase alphabetic character to its equivalent lowercase character. It returns all other characters unchanged. The toupper() function converts a lowercase alphabetic character to its uppercase equivalent. It returns all other characters unchanged.

Listing: Character Conversion Example


#include <stdio.h>

#include <ctype.h>

int main(void)

{

char s[] ="** DELICIOUS! lovely? delightful **";

int i;

for (i = 0; s[i]; i++)

putchar(tolower(s[i]));

putchar('\n');

for (i = 0; s[i]; i++)

putchar(toupper(s[i]));

putchar('\n');

return 0;

}

Output:

** delicious! lovely? delightful **

** DELICIOUS! LOVELY? DELIGHTFUL **