Where is the GNU Pascal Compiler?

It appears that gpc was removed from Debian (and subsequently Ubuntu) in February 2011 due to the project being unmaintained/discontinued.

PPA versions of the GNU Pascal Compiler for Ubuntu can be downloaded from https://launchpad.net/~ueter/+archive/ubuntu/gpc-3.4

Not exactly gpc, but if you don't mind an alternative, you could use Free Pascal. This will install the IDE and compiler:

sudo apt-get install fp-ide

Note that the IDE is terminal based. To start it from the prompt:

fp

For reference, see http://fusharblog.com/installing-free-pascal-in-ubuntu/