The strxfrm function from string.h header in C programming language is used to transform a string in a locale-specific way such that it can be sorted according to the collation sequence of the current locale.

The function has the following signature:

size_t strxfrm(char *dest, const char *src, size_t n);

The function takes three arguments:

• dest: A pointer to the destination buffer where the transformed string is to be stored.
• src: A pointer to the source string that needs to be transformed.
• n: The maximum number of characters that can be written to the destination buffer, including the terminating null character.

The function returns the length of the transformed string, which can be longer than the original string. The transformed string is stored in the destination buffer pointed to by dest.

It is important to note that strxfrm function is affected by the current locale, so the results may differ depending on the system's settings.