Historical Background

 Historical Background The history of electronic computers is not very old
. It came into existence in the early 1950,s and during the first two decades of its existence it remained as a centralized system housed in a single large room
. In those days the computers were large in size and were operated by trained personnel
. To the users it was a remote and mysterious object having no direct communication with the users
. Jobs were submitted in the form of punched cards or paper tape and outputs were collected in the form of computer printouts
. The submitted jobs were executed by the computer one after the other, which is referred to as batch mode of data processing
. In this scenario, there was long delay between the submission of jobs and receipt of the results
. In the 1960,s computer systems were still centralize, but users provided with direct access through interactive terminals connected by point-to-point low-speed data links with the computer
. In this situation, a large number of users, some of them located in remote locations could simultaneously access the centralized computer in time-division multiplexed mode
. The users could now get immediate interactive feedback from the computer and correct errors immediately
. Following the introduction of on-line terminals and time-sharing operating systems, remote terminals were used to use the central computer.