System software and operating systems
System software runs and manages the computer itself; the operating system sits between the user, the applications and the hardware.
Layers of a computer system
The operating system is the middle-man. Applications never talk to the hardware directly.
Functions of an operating system
- Starts the computer (booting) and loads itself into memory.
- Manages the processor: decides which program runs, allowing multitasking.
- Manages memory: gives RAM to programs and frees it afterwards.
- Manages files and folders on storage: create, copy, delete, organise.
- Controls input and output devices through device drivers.
- Provides the user interface: graphical (icons, windows) or command line.
- Provides security: user accounts, passwords and access rights.
Other system software
| Type | Purpose | Examples |
|---|---|---|
| Utility programs | Maintain, protect and tidy the computer | Antivirus, backup, disk clean-up, file compression (ZIP) |
| Device drivers | Let the operating system work with one particular device | Printer driver, graphics card driver |
| Language translators | Turn program code written by people into machine code | Compiler, interpreter, assembler |
Compiler vs interpreter
An assembler translates assembly language (short codes such as ADD) into machine code.
Where operating systems are used
| Kind | Examples |
|---|---|
| Desktop and laptop | Windows, macOS, Linux |
| Mobile | Android, iOS |
| Server | Windows Server, Linux |
| Embedded | Built into machines such as ATMs, POS terminals and smart TVs |
Many Sri Lankan offices run Windows on their desktops while staff use Android or iOS phones for company apps. IT staff keep antivirus utilities updated so that one infected pen drive cannot spread malware across the office network.
Short answer: “What is a device driver?” A small system program that lets the operating system communicate with and control a particular device, such as a printer.
Structured question: “Distinguish between a compiler and an interpreter.” A compiler translates the whole program before running and makes an executable. An interpreter translates and runs one line at a time.
Essay: “Explain the functions of an operating system.” Define the OS, draw the layers, then explain booting, processor, memory, file and device management, user interface and security.
The OS is the manager: it manages the processor, memory, files and devices, protects users (security) and gives you the interface.