Understand the need for, and functions of, operating systems (OS) and…

The idea

An operating system is system software that sits between the user, the application software and the hardware, so the need for it arises because raw hardware cannot be used conveniently or safely on its own. Its functions include managing memory, managing processor time (scheduling), managing input and output devices, managing files and providing a user interface. Utility programs are small, focused tools that maintain or protect the system, for example a disk defragmenter, a backup utility, an antivirus scanner or a compression tool. The key distinction is that the OS runs and coordinates the whole machine, whereas a utility performs one specific housekeeping or security job, often launched from within the OS. A question may ask why an OS is needed, what a named function does, or which item is a utility rather than an OS.

What earns the marks

• States that an operating system is system software that manages hardware and provides a platform on which application software runs.
• Identifies at least two OS functions, such as memory management, processor scheduling, device/input-output management, file management and providing a user interface.
• Explains the need for an OS: without it, users and applications could not easily or safely control hardware, share resources or store files.
• Distinguishes utility programs from the OS: a utility performs a specific maintenance, security or housekeeping task rather than coordinating the whole system.
• Gives a correct example of a utility program, such as a backup tool, antivirus, disk defragmenter or file compression tool, and says what it does.

Common mistakes and how to put them right

• Treating an application such as a word processor as an operating system.

  Put it right by classifying it as application software that runs on top of the OS.

• Confusing a utility program with the OS.

  Put it right by noting the OS coordinates the whole machine while a utility performs one focused task.

• Listing only 'provides a user interface' as the sole function.

  Put it right by adding resource management functions such as memory, processor time, devices and files.

• Assuming the OS is hardware.

  Put it right by stating it is system software.

Exam tips

• Learn the functions as a short list you can recall quickly: memory, processor time, devices, files and user interface.
• When asked for a utility, name it and add one clause saying what it does, so the example is clearly a utility.
• Read the question stem to check whether it asks for the need for an OS, a function of the OS, or an example of a utility, and answer that specific point.