Evolution of operating systems

Early computer were capable of performing only one job or task at a time.this from of computer opertaion is often called single-user batch processing.the computer runs a single program at a time while processing data in group or batches.In these early system,users generally submitted their jobs to the computer center on desk of punched cards.Users often had to wait hours or even days before printouts were returned to their desks.software system called oprating system were devloped to help make it convenient to use computer.Early operating systems managed the smooth transition between jobs.This minimized the time it look for computer operator to switch between jobs,and hence increased the amount of work,or throughtput,computer could process.As computer became more powerful,it became evident that single-user batch processing rarely utilized the comuter's rwsourcess efficiently.Instead,it was thought that many jobs or task could be made to share the resources of the computer to achieve better utilization.This is called multiprogramming.Multiprogramming involves the "simultaneous" operation of many jobs on the computer-the computer share its resources among the jobs competing for its attention.With early multiprogramming operating system,users still submitted jobs on decks of punched cards and waited hours or days for results.In the 1960s,several groups in industry and the universities pinoeered timesharing operating systems.Timesharing is a special case of multiprogramming in which users access the computer though terminals,typically devices with keyboards and screens.In a typical timesharing computer system,they may be dozens or even hundredsnof users sharing the computer at once.The computer does not actually run all the users simultaneously.Rather,it runs a small portion of one user's jobs and then moves on to service the next user.The computer does this so quickly that it may provide service to each user several times per second.Thus the user's programs appears to be running simultaneously.An advantage of timesharing is that the user receives almost immediated responses to requests rather than having to wait long periods for results as with previous modes of computing.