BEN10, "command line" is simply user input at a text-based terminal... before fancy windows interfaces were invented. When you just type the name of the program at a prompt. The program's parameters (or arguments) are entered in following the program name.
testprog hello 12 -Q
would execute the program "testprog" and pass it "hello", "12", and "-Q". These parameters are available in the program: number of parameters is in the variable argc and the values are in the argv array.
