Do a search on "bash script" a bit. I think this is the thing that you need. But if you just want to run processes one after another, just separating the program with ";":
xxx -s ddd; ddd -f lll mmm; kkk -v lll;
in the terminal will do. The programs will run after the previous one finished its job.
If you want to run specific program at specific time, "at" command is fine.