Format
#include <ctype.h>
int tolower(int C);
int toupper(int c);Language Level: ANSI
Threadsafe: Yes.
Locale Sensitive: The behavior of these functions might be affected by the LC_CTYPE category of the current locale. For more information, see Understanding CCSIDs and Locales.
Description
The tolower() function converts the uppercase letter C to the corresponding lowercase letter.
The toupper() function converts the lowercase letter c to the corresponding uppercase letter.
Return Value
Both functions return the converted character. If the character c does not have a corresponding lowercase or uppercase character, the functions return c unchanged.
Example that uses toupper() and tolower()
This example uses the toupper() and tolower() functions to change characters between code 0 and code 7f.
#include <stdio.h>
#include <ctype.h>
int main(void)
{
int ch;
for (ch = 0; ch <= 0x7f; ch++)
{
printf("toupper=%#04x\n", toupper(ch));
printf("tolower=%#04x\n", tolower(ch));
putchar('\n');
}
}Related Information