It is hoped that the student has built a couple of registers to store numbers and a adder so that the process can be seen. I think every student should build a register and adder. It could be done in science class. Relays could be used so that the simple process of storing numbers as electrical voltage could be observed more directly. If you have computers why not use them and study the most basic mode in which they will operate.
Students love it.
They can write simple programs. I found that there was much more interest than in the little trainer. The knowledge transfers to higher level programming. Computers that many school districts are dumping are fine for this purpose. I used a couple of the oldest IBMs for a while.