The assumption is that your isem program is caught in an infinite loop and you want to stop execution of ISEM.
The following will let you kill the ISEM process and thus terminate your program.
See if you can suspend the job with
Control-Z
find the background job number for ISEM with:
% jobs
This will print out a list of background jobs, usually:
[1] + Suspended isem
Find the line that contains ISEM and issue the kill command with the corresponding ID number. For example with the output above, the kill command would be:
kill %1
Otherwise find the process ID number for isem by typing in another terminal window or by putting ISEM in the background with CTRL-Z:
% ps -a | grep isem
28007 pts/94 0:09 isem
issue the kill command with the process ID number: