An important task, therefore, is that of the proper scheduling of different tasks. The OS sees to it that all conflicts are resolved and each application gets a fair share of the common resources, often in accordance with a certain priority schedule. Each application needs to share the CPU, main memory and all peripheral devices. Today’s computers handle many applications at the same time: you could be downloading a file from the Internet at the same time as you update a spreadsheet that is embedded within a word-processing document (while at the same time your virus scanner is running in the background). Their complexity stems from the increasing number of functions that an operating system is required to handle. Today’s operating systems are true marvels of engineering and rate among the most complex artifacts designed by humans. At the opposite end of the market, we find that the leading operating system for the IBM compatible Personal Computers is Microsoft Windows (having all but replaced its predecessor MS-DOS) although Mac-OS and Unix variants such as Linux also have strong followings.įigure 5-4: Some operating system components Most mainframe computers have a proprietary operating system, such as IBM’s MVS or Siemen’s BS2000.

It allows the computer to run a number of different applications apparently simultaneously, and shares resources such as printers between a number of different users, while at the same time performing those functions that are critical to the correct operating of the computer system, regardless of which application is running.ĭifferent types of computers may require different operating systems. The operating system is an essential piece of software that resides on virtually every computer. But the one thing that all these machines would definitely have is an operating system (OS). It is also possible (although unlikely) that the PC of a programmer could provide development tools only, and no other commercial applications. The PC of a business end-user will quite commonly provide a number of different application programs, but no program development tools.

Differences between operating systems