OS and utility programs

Why Does a Computer Need an Operating System?

Without an operating system (OS), a computer is simply a collection of hardware components with no way to coordinate them. The CPU, RAM, storage drives, and input/output devices cannot communicate with each other directly - they need a central manager. The OS provides this management, loading first when the computer starts and remaining in control for as long as the computer is running.

The OS also acts as the platform on which all application software runs. Applications do not interact with hardware directly - they make requests to the OS, which handles the hardware on their behalf. This means application developers can write software without needing to know the exact technical details of every possible piece of hardware their program might encounter.

Hardware (CPU, RAM, storage, I/O devices) Operating System Application Software (word processors, browsers, games...)

The OS sits between hardware and applications, managing communication in both directions.

What the OS Manages

AQA specifies five key areas that the operating system is responsible for managing. Each area addresses a distinct challenge in running a computing system reliably and efficiently.

Operating System Processor(s) Memory I/O Devices Security Applications
Processor management

The OS decides which processes run on the CPU and for how long, using multitasking to rapidly switch the processor between programs. On a computer with a single core, this switching happens so quickly that all programs appear to run simultaneously. The OS also manages priority - some processes (e.g. a real-time audio driver) may be given higher priority than others.

Memory management

The OS allocates areas of RAM to each running program, tracks which addresses are in use, and prevents programs from reading or writing to each other's memory. When a program closes, the OS reclaims its allocated memory for reuse. Without this, one program could accidentally or maliciously corrupt another's data.

Input/output (I/O) device management

The OS communicates with hardware devices such as keyboards, mice, printers, monitors, and storage drives via device drivers. A device driver is a small program that translates the OS's standard instructions into the specific signals a particular device understands. This means applications can print a document without knowing anything about the printer's technical specifications.

Application management

The OS loads applications into memory, allocates resources to them, manages the switching between them, and terminates them cleanly when they close or crash. It also provides services that applications call upon - such as file access, network communication, and drawing graphics on screen - through a set of programming interfaces.

Security management

The OS enforces user accounts and access permissions, controlling who can log in and what each user is allowed to do. It restricts which programs can access sensitive system areas, logs activity, and may include a firewall to control network access. Without OS-level security, any program or user could access or modify any file or setting on the system.

Utility Programs

Utility programs are system software tools that maintain, optimise, or protect the computer. They serve the computer system rather than the end user, which is why they are classified as system software. Common examples include:

  • Antivirus software - scans for and removes malware, protecting data and system integrity.
  • Disk defragmenter - reorganises fragmented data on hard disk drives so related sectors are stored contiguously, improving read speed. Not applicable to SSDs.
  • Backup software - creates copies of files to a separate location, enabling recovery after data loss.
  • File compression - reduces file sizes for storage or transfer (e.g. ZIP format).
  • Encryption tools - scramble file contents so only authorised users with the correct key can read the data.

 Key Takeaways

  • The OS is essential: it manages all hardware resources and provides the platform on which application software runs.
  • The OS manages five key areas: processor(s), memory, I/O devices, applications, and security.
  • Device drivers allow the OS to communicate with specific hardware components without applications needing hardware-specific knowledge.
  • Utility programs (antivirus, disk defragmenter, backup tools, file compression, encryption) maintain and protect the system and are classified as system software.