toupper - transliterate lowercase characters to uppercase
int toupper(int c);
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.
The toupper() function has as a domain a type int, the value of which is representable as an unsigned char or the value of EOF. If the argument has any other value, the behavior is undefined. If the argument of toupper() represents a lowercase letter, and there exists a corresponding uppercase letter [CX] (as defined by character type information in the program locale category LC_CTYPE ), the result shall be the corresponding uppercase letter. All other arguments in the domain are returned unchanged.
Upon successful completion, toupper() shall return the uppercase letter corresponding to the argument passed.
No errors are defined.
setlocale(), the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 7, Locale, <ctype.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
Extensions beyond the ISO C standard are marked.