Printing And Plotting

One of the most use full and popular forms of output is called hard copy, which
Is simple output paper from a printer. Printer with different speed, feature and capabilities are available. Some can be set up to accommodate different paper forms such as blank check forms, invoice forms and so forth. Newer printers allow businesses to create customized printing output for each customer from standard paper and data input using full color.
The speed of the printer is typically majored by the number of pages printed per minute (PPM). Like a display screen, the quality, or resolution, of a printer’s output depend on the number of dots printed per inch. A 600-dpi (dots per inch) printer print more clearly and a 300-dpi printer. A recurring cost of using a printer is the ink-jet or laser cartridge that must be replaced every few thousand of pages of output.
Plotters are a type of hard copy output devices are used for general design work.
Businesses typically use these devices to generate paper or acetate blueprints,
Schematics, and drawings or new products onto paper or transparencies. Standard plot widths are 
24 inches and 36 inches, and the length can be as per the need-from a few inches to feet. 

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.