Centralized Computing

Centralized Computing

The earliest computers were large, expensive, and difficult to manage. Originally, these large mainframe computers were not networked in the sense you are familiar with today. Jobs were entered into the system by reading commands from card decks. The computer would execute one job at a time and generate a printout when the job was complete. Terminals, which came later, enabled users to interact with the centralized computer, but terminals were merely input/output devices that had no independent processing power. All processing still took place on the mainframe, hence the name centralized computing. Networks, therefore, served little purpose other than to deliver commands to and results from the powerful centralized processing device. Large IBM and Digital (DEC) networks often still operate on this model, but Microsoft has largely ignored it.

In summary, the centralized computing model involves the following:

All processing takes place in the central, mainframe computer.
Terminals are connected to the central computer and function only as input/output devices.
Networks may be employed to interconnect two or more mainframe computers. Terminals connect only to the mainframe, never to each other.

This early computing model worked well in large organizations, but was not flexible and did not scale down to meet the needs of smaller organizations. As such, new ways of sharing information were needed to allow computing power to be shared efficiently on smaller networks.