I'm guessing the compiler is not in your path. Your "execution path" is a list of directories which is searched for executables when you attempt to enter a command.
What shell are you using, tcsh or bash? To find out, do:
grep user_name /etc/passwd
For tcsh, do the following:
The output will be a list of directories. If /usr/bin is not in your 'execution path', it will not be found. You could fix it by putting a line like this in your shell startup config file (.tcshrc or .cshrc):
set path = ($path /usr/bin
You can do the equivalent things in bash, but the specific syntax is different, so I'll leave that to someone more familiar with bash.
Oh, to find out if you have the gcc compiler,
ls -l /usr/bin/gcc
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