Memory protection in the old days: There are three memory mapped input/output areas and these are named FRED, JIM and SHEILA. SHEILA contains all the machine's

Memory protection in the old days: There are three memory mapped input/output areas and these are named FRED, JIM and SHEILA. SHEILA contains all the machine's internal memory mapped devices, such as the analogue to digital converter, and should be treated with considerable respect.