Pascal wasn't case sensitive, so it was mostly a matter of style.
On Modula-2 and Oberon languages and their descendants keywords are uppercase and the languages are case sensitive.
But you could anyway write in lowercase and let the editor format the code for you, no need for banging the shift key all the time. :)
Actually I kind of like having keywords as uppercase, it means on a poor man's teletype or modern black-and-white printer without formatting, it is easier to spot the keywords versus the rest of code.
