This is an inbuilt function function provided by PPWIZARD.
This function takes a single parameter and returns it in upper case. The translations are performed for english characters (a-z) by default but it is possible to configure PPWIZARD for other languages.
To convert to lower case you can use the ToLowerCase() function.
To configure the case conversion see the "Upper/Lower Case Configuration" section.
Note that for more complex character translations you should have a look at the standard rexx translate() function (which this what this function uses internally).