4.3 The permanent memory
Passing to the right of the RAM memory and entering inside the computer, you will find the control unit, which has the role of reading and executing machine instructions. Continuing to the left, on the floor you see the magnetic drum memory unit. This is a permanent memory, whose content persists between one power-on and another, and can hold 72 kB, double the computer's temporary memory. The cables coming out of it were originally connected to the calculator via bus.