Academy Computer Science Systems software

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Paper 1 · J277/01 · unit 1.5

Systems software

Operating system jobs (UI, memory, multitasking, peripherals, users, files) and utilities (encryption, defrag, compression). Open practice and quiz.

Everything on this course is open. Skip, jump, retry. Nothing is locked and there is no required order.

The software you did not install for fun: the operating system, and utilities that tidy, encrypt, and compress. Short unit — still a favourite for “describe the purpose of…” questions.

1.5.1 Operating systems

An OS manages hardware and provides a platform for applications. OCR’s list of jobs:

User interface

GUI (windows, icons, pointers) or CLI (typed commands). The OS presents this so you are not flipping CPU flags by hand.

Memory management

Decides which process gets which RAM, protects processes from overwriting each other, works with virtual memory (see 1.2.1).

Multitasking

Gives the illusion of many programs at once by scheduling slices of CPU time. One core still does one thing at a time; switching is fast.

Peripheral management and drivers

Printers, keyboards, GPUs — the OS talks to them through device drivers (translator software for that model of hardware).

User management

Accounts, passwords, access rights. Different users can have different files and privileges.

File management

Creating, naming, copying, moving, deleting files; directories; knowing which sectors on disk belong to which file.

Without an OS you would boot a single dedicated program (see embedded systems) or toggle switches on a front panel. General-purpose machines need this layer.

1.5.2 Utility software

Utilities do extra jobs the OS may not do (or not do in a way you invoke day to day). OCR names three:

Utility Purpose
Encryption software Scramble files/disks so stolen media is unreadable without the key
Defragmentation On magnetic HDDs, files get split into fragments; a defragger puts blocks back together so the head moves less. Do not defrag an SSD as an exam answer — it does not help and wears flash
Compression Make copies smaller for storage or email (see 1.2.5)

The spec also wants you to know utility software is needed for additional tasks the OS may not carry out. Backup tools, disk checkers, and anti-malware are the same idea if a question is broader, but learn the three named ones cold.

Exercises are “purpose in one sentence” drills — that is how Paper 1 marks these.

Practice · optional · answers on this page

Exercises

Do as many or as few as you like, in any order. Hints and a model answer sit under each task.

1.5.1 · e1 paper

Name the OS job

Which OS function? 1. Two applications appear to run at once on one core. 2. A new graphics card needs extra software before games will see it. 3. Lewis and Dad have separate accounts and cannot see each other’s files. 4. RAM is shared between Chrome and Python without them overwriting each other. 5. You rename a folder of revision notes.
Hint
Multitasking, drivers/peripherals, user management, memory, file management.
Show a model answer
1. Multitasking / scheduling 2. Peripheral management (device driver) 3. User management 4. Memory management 5. File management
1.5.1 · e2 paper

GUI vs CLI — two each

Two advantages of a GUI for a new user, two advantages of a CLI for a technician.
Hint
Learning curve vs speed, scripting, resources.
Show a model answer
GUI: easier to learn; discoverable (you can see icons); fewer typing errors. CLI: faster for experts; easy to automate with scripts; uses fewer resources; works when graphics are broken.
1.5.2 · e3 paper

Which utility?

1. A stolen USB stick should be unreadable. 2. An old HDD has become slow; files are in pieces. 3. Emailing a 40 MB folder of text logs through a 10 MB limit. For each: the utility, and one sentence of purpose.
Hint
Encryption, defragmentation, compression.
Show a model answer
1. Encryption software — ciphertext without the key 2. Defragmentation — contiguous blocks, less head travel (HDD only) 3. Compression — smaller file to send
1.5.2 · e4 think

Why not defrag the SSD?

In two sentences, why defragmentation is for HDDs and a bad idea as “maintenance” on an SSD.
Hint
Moving parts vs random-access flash; write wear.
Show a model answer
HDDs have a moving head, so scattered blocks cost time; SSDs can access any cell equally quickly, so “putting the file together” does not speed it up. Extra writes from defrag wear flash and shorten SSD life.

Check yourself · not a gateway

Quiz

Mark it, reveal it, or skip it. A low score does not close anything. Try again as often as you want.

1 1.5.1 Device drivers are used so that…
2 1.5.1 Which of these are functions of an operating system? (Select all that apply)
3 1.5.1 Multitasking on a single core works by…
4 1.5.2 Defragmentation is used on a magnetic HDD to…
5 1.5.2 Encryption utility software is used to…
6 1.5.1 An operating system is application software like a browser or a game.