The toupper function is used to convert lowercase alphabet to uppercase. If the character passed is a lowercase alphabet then the toupper function converts a lowercase alphabet to an uppercase alphabet. Return value. Lowercase version of ch or unmodified ch if no lowercase version is listed in the current C locale. NoteLike all other functions from, the behavior of std::tolower is undefined if the argument's value is neither representable as unsigned char nor equal to EOF.To use these functions safely with plain char s (or signed char s), the argument should first be converted to.
Name
toupper, tolower - convert letter to upper or lower case
Synopsis
Description
toupper() converts the letter c to upper case, if possible.
tolower() converts the letter c to lower case, if possible.
If c is not an unsigned char value, or EOF, the behavior of these functions is undefined.
Return Value
The value returned is that of the converted letter, or c if the conversion was not possible.
Conforming to
C89, C99, 4.3BSD.
Bugs
The details of what constitutes an uppercase or lowercase letter depend on the current locale. For example, thedefault 'C'' locale does not know about umlauts, so no conversion is done for them.
In some non-English locales, there are lowercase letters with no corresponding uppercase equivalent; the German sharp s is one example.
The C library function int tolower(int c) converts a given letter to lowercase.
Declaration
Following is the declaration for tolower() function.
Parameters
c − This is the letter to be converted to lowercase.
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Return Value
This function returns lowercase equivalent to c, if such value exists, else c remains unchanged. The value is returned as an int value that can be implicitly casted to char.