| Function | Header File | Description |
| strlwr | string.h | Converts any uppercase letters in a string to lowercase. |
| strupr | string.h | Converts any lowercase letters in a string to uppercase. |
| _toascii | ctype.h | Converts a value to its ASCII character equivalent. |
| tolower | ctype.h | Converts a character to lowercase. |
| _tolower | ctype.h | Converts an uppercase ASCII character to lowercase. |
| toupper | ctype.h | Converts a character to uppercase. |
| _toupper | ctype.h | Converts a lowercase ASCII character to uppercase. |
| towctrans | wctype.h | Performs wide-character mapping using wctrans.** |
| towlower | wctype.h | Converts an uppercase wide character to a lowercase. |
| towupper | wctype.h | Converts a lowercase wide character to uppercase. |
| wctrans | wctype.h | Describes a wide-character mapping.** |
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Alphabetical Listing of IBM C and C++
Compilers Functions and Macros