Small letters as input but capital letters as output

Is it possible to define (or is there already) a macro which takes small letters as input but gives the same letters in capital as output?

Example:

\CapLet{horse} and \CapLet{fish}


wiht the output

HORSE and FISH

• \MakeUppercase? – cmhughes Jun 13 '13 at 23:39

\MakeUppercase converts the case of its argument to UPPER CASE.
\documentclass{article}

It uses the TeX primitive \uppercase internally. A comparable \MakeLowercase exists.