OS Functions · Process Management · Memory Management · User Interfaces
CSZoneEdexcel GCSE Computer Science 1CP2
What Does an OS Do?
The Bridge Between Software and Hardware
The operating system (OS) is system software that manages hardware resources and provides services for application software. Without an OS, user programs cannot run — examples: Windows, macOS, Linux, iOS, Android.
Process management — controls which programs run, in what order, and for how long
Memory management — allocates RAM to programs; prevents one program accessing another's memory
File management — organises storage; creates/renames/deletes files and folders
Device management — communicates with peripherals via device drivers
Process Management
Multitasking and Scheduling
Multitasking: the OS rapidly switches between processes, giving the illusion that multiple programs run simultaneously. The CPU can only run one process at a time, but switches so fast users don't notice.
Scheduling algorithm — decides which process gets CPU time next. Methods: round robin, priority scheduling
Context switching — saving the state of one process before loading another; allows resumption later
User Interfaces
How Users Interact with the OS
GUI (Graphical User Interface): windows, icons, menus, pointer (WIMP). Intuitive for beginners; requires more system resources. e.g. Windows desktop.
CLI (Command Line Interface): text commands typed by user. Faster for experts; requires knowledge of commands; uses fewer resources. e.g. Linux terminal.
Security:OS manages user accounts and permissions — controls who can access what files and run what programs
Exam Practice
Have a go at this question
Edexcel-style question
Describe two functions of an operating system.
4 marks
Memory management: the OS allocates RAM to running programs [1] and ensures that one program cannot access or overwrite the memory used by another, preventing crashes [1]. Process management: the OS controls which processes run on the CPU [1] and schedules them to give each program CPU time, enabling multitasking [1].
Key Takeaways
What to Remember
OS functions: process management, memory management, file management, device management
Multitasking: CPU rapidly switches between processes — appears simultaneous
GUI: windows/icons/mouse — easy to use; CLI: text commands — powerful for experts
OS also manages security: user accounts, permissions, access control