5.1 Operating Systems

2026 Syllabus Objectives

By the end of this topic, you should be able to:

  • explain why a computer system needs an Operating System (OS)

  • explain the main management tasks carried out by the OS:

    • memory management
    • file management
    • security management
    • hardware management, including input, output, and peripherals
    • process management

  • explain why utility software provided with an OS is needed, including:

    • disk formatter
    • virus checker
    • defragmentation software
    • disk contents analysis / disk repair software
    • file compression
    • back-up software

  • explain what program libraries are

  • explain why software developers use code from program libraries

  • explain the benefits of using library files, including Dynamic Link Library (DLL) files

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What is an Operating System?

An Operating System, usually called an OS, is the main system software that allows a computer to work properly. It acts as a bridge between the user, the application software, and the hardware.

The hardware is the physical part of the computer, such as the processor, memory, storage devices, keyboard, mouse, printer, and screen. The user normally does not control this hardware directly. Instead, the OS manages it and makes it easier to use.

Without an OS, a computer would be very difficult to use. A user would need to know exactly how to control hardware devices and where data is stored. The OS hides this complexity. For example, when you save a file, you do not need to know the exact place on the disk where each piece of data goes. The OS does that for you.

So, a computer system needs an OS because it:

  • provides a way for the user to interact with the computer
  • manages hardware resources
  • manages files and storage
  • manages running programs
  • provides security features
  • makes application software able to run

In simple words, the OS is the manager of the whole computer system.

Why a computer system requires an OS

A computer system requires an OS because modern computers do many jobs at once and have many parts that need to be controlled carefully. The OS makes sure everything works together in an organised way.

1. It provides a user interface

A user interface is the way a person communicates with the computer system. The OS provides this interface.

There are different types of interface:

  • Command Line Interface (CLI) The user types text commands. This is often used by advanced users because commands must be entered correctly.

  • Graphical User Interface (GUI) The user interacts with windows, icons, menus, and pointers. This is more visual and easier for many users.

  • Menu interface The user chooses from a series of menus or options. This is common in machines like ticket machines or vending machines.

  • Natural Language Interface (NLI) The user speaks or types normal language, and the system responds. Voice assistants are examples of this.

The syllabus focus is not on learning every interface type in detail, but it is important to understand that the OS gives the user a practical way to control the computer.

2. It manages the computer’s resources

A computer has limited resources such as CPU time, RAM, and storage space. The OS decides how these resources are shared. This is very important when many programs are open at the same time.

3. It allows programs to run

Application software, such as word processors, browsers, and games, depends on the OS. The OS provides the basic services these programs need, such as opening files, sending data to a printer, or using memory.

4. It keeps the system organised and secure

The OS controls access to files, allows user accounts to be set up, and helps protect the system from misuse or damage.

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