Operating systems and utility software
Computer Science · GCSE · The School
An operating system manages everything else
An OPERATING SYSTEM manages a computer's hardware and software so applications do not each have to control the hardware directly. It provides a user interface, manages files, allocates memory, schedules which program the CPU works on next, and manages the peripherals connected to the machine.
Memory management: sharing limited RAM
Several programs run at once, but RAM is limited, so the operating system allocates each program the memory it needs and keeps one program's memory separate from another's, so a fault in one does not corrupt another. When RAM genuinely runs short, it can use part of the hard disk as VIRTUAL MEMORY, at a real cost in speed.
Multitasking: one CPU, many programs
With one CPU core, only one instruction genuinely executes at any instant. The operating system creates the APPEARANCE of running several programs at once by switching between them very rapidly, giving each a short slice of CPU time in turn. The switching is too fast for a person to notice, though heavy demand can still slow every program down.
A worked example: opening too many programs
A laptop with 8 GB of RAM has several browser tabs, a video editor and a game open together. Each program has been allocated its own share of RAM by the operating system. Once total demand exceeds 8 GB, the operating system starts swapping some data out to virtual memory on the disk — noticeably slower than RAM, which is exactly why the whole machine can feel sluggish under heavy load.
Utility software: maintaining, not creating
UTILITY SOFTWARE keeps a system running well rather than doing the user's actual work. Anti-virus scans for and removes malicious software. Defragmentation reorganises fragmented file data on a mechanical hard disk to speed up access. Compression software reduces file size for storage or transfer. Backup software copies data to protect against loss.
Choosing the right utility for the right risk
Anti-virus protects against a program actively attacking the system. Backup protects against loss from hardware failure, theft or ransomware — a problem anti-virus alone cannot solve, since it cannot undo damage already done. Firewall software controls what network traffic is allowed in or out, a different risk again from either. Naming which specific risk a utility addresses, not just "it keeps the computer safe", is what a full answer does. A system running several of these together is protected against different failures, not the same one repeated.