AS · Practice questions · Why a computer needs an operating system

Manage the resources.

Six original Cambridge-style questions on the need for an operating system and its key management tasks, with mark-scheme solutions.

Original questions All questions on this page are original work, written in the Cambridge AS & A Level style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Keep these straight

Name the task, then the detail.

Why an OS: hides hardware complexity, provides an interface, a platform for applications, and shares resources.
Memory and process: RAM allocation and protection; scheduling processor time.
File and security: directory structure and file operations; accounts, passwords, access rights, firewall.
Hardware: device drivers, interrupts, buffers and queues for input/output.

Explain

[3 marks]

Explain why a computer system requires an operating system.

It provides a user interface so the user can communicate with the computer. ✓
It hides the complexity of the hardware: applications use OS services instead of controlling hardware directly. ✓
It manages resources (processor, memory, storage, devices) and shares them between programs and users. ✓

Recall

[4 marks]

Identify four key management tasks carried out by an operating system.

Memory management. ✓
File management. ✓
Security management. ✓
Hardware (input/output/peripheral) management. (Also accept process management; one mark each, up to four.) ✓

Explain

[3 marks]

Describe how an operating system carries out memory management.

It allocates memory (RAM) to a process when it is loaded and de-allocates it when the process ends. ✓
It keeps track of which areas of memory are free and which are in use. ✓
It protects each process's memory so that one process cannot access or overwrite another's (and uses virtual memory if RAM is full). ✓

Explain

[3 marks]

Describe three ways the operating system carries out security management.

User accounts with a username and password, so only authorised users can log in. ✓
Access rights (permissions) that control which users can read, write or delete each file or folder. ✓
A firewall and automatic security updates to block unauthorised access and fix vulnerabilities. ✓

Apply

[4 marks]

A user is downloading a large file while editing a video and printing a document. For each, identify the OS management task: (a) the printer receives the document a block at a time from a buffer (b) the video editor and the download both get processor time (c) the downloaded data is saved into the Downloads folder (d) the video editor is given extra RAM.

(a) Hardware (input/output, peripheral) management. ✓
(b) Process management. ✓
(c) File management. ✓
(d) Memory management. ✓

Analysis

[2 marks]

A student says: "Process management and memory management are the same thing because both are about running programs." Explain why the student is wrong.

Process management schedules the processor: it decides which process runs on the CPU and for how long. ✓
Memory management allocates and protects RAM for each process: it decides where each process is stored in memory. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.