Mainframe Systems

• The earliest computers, developed in the 1940s, were programmed in machine language and they used front panel switches for input. The programmer was also the operator interacting with the computer directly from the system console.
• First commercial systems: Enormous, expensive and slow. I/O: Punch cards and line printers.
• The term probably had originated from the early mainframes, as they were housed in enormous, room-sized metal boxes or frames (See Fig. 1). Later the term was used to distinguish high-end commercial machines from less powerful units.

  Figure 1: An IBM 704 mainframe.

  
• Single operator/programmer/user runs and debugs interactively:
  • Standard library with no resource coordination.Monitor that is always resident
    • initial control in monitor,
    • control transfers to job,
    • when job completes control transfers back to monitor.
• Poor throughput (like amount of useful work done per hour) and poor utilization (keeping all devices busy). Inefficient use of hardware.