7. Program Input Method
Because they provide immediate access, the most satisfactory program storage media are magnetic disks and drums, followed by the IBM tape. The most satisfactory cheap device for input of programs is the high-speed, punched-tape reader, but the advantages of using small "cartridge-type" magnetic tapes have recently been emphasized. Recently, card readers have appeared which are much cheaper than the older IBM models. They can read 200-300 cards per minute. They cost about $2000 plus interfacing. Examples: Soroban, General Devices, Uptime.
A simple means of restoring the basic loader program (other than toggling!) is desirable. Many computers have this feature, e.g., the IBM 360 series; the SDS Sigma 2, Sigma 5, and 910 PDP-9.
8. Memory Protection
Hardware memory protection is necessary in multiprogram systems. It is very helpful in any machine with a batch-processing resident monitor and in other special situations.
9. Parity Check
This feature is useful for purposes as detecting memory failures, but it is usually not worth its cost in computer speed and in capital investment in the case of a small system.
10. Ease and Cost of Interfacing
This is a big subject, partly because the organization of computers for input and output of data varies with the manufacturer. Some computers such as the Hewlett-Packard and the DEC models are especially easy to interface, whereas the automatic channels of the SDS Sigma computers and the ordinary IBM machines (e.g., the 360 series) are very difficult. The IBM machines require an expensive control unit. It is said that before a competent engineer could order plug boards for Sigma interfacing he would have to study the system for a month or two. However, once interfaced, these machines permit rapid input of data. Interfacing a $5000 Calcomp plotter to the automatic channel of an IBM or Sigma series machine may cost much more than the cost of the plotter.