AS Computer Science 9618: File Management, User Accounts and Program Libraries

Jamal shares a family laptop with his younger sister Aisha. Each of them logs in to their own separate user account, protected by its own password. Jamal keeps his growing collection of coursework documents organised inside several folders on the laptop's hard disk, but he has never made a backup copy of this coursework anywhere else.

Jamal is also learning to write simple programs in a high-level language. For one task, he calls a ready-made routine from a graphics library to draw a circle on the screen, rather than writing his own code to do this; the library routine is supplied to him as a Dynamic Link Library (DLL) file.

(a) Explain how the operating system's file management lets Jamal organise his coursework documents into folders on the laptop's hard disk, and later locate a particular file again. [2]

(b) Explain how the operating system's management of user accounts prevents Aisha from opening or changing Jamal's coursework documents when she is logged in under her own account. [2]

(c) State a utility program Jamal should use regularly to protect against permanently losing his coursework if the laptop's hard disk were to fail, and describe what it does. [2]

(d) State what is meant by a program library, and explain one reason why Jamal calls a ready-made routine from a graphics library, supplied as a DLL, instead of writing his own code to draw a circle. [2]

Part (a): File management

The operating system’s file management allows Jamal to create folders on the laptop’s hard disk and organise his coursework documents inside them, building up a directory structure that groups related files together. For every file, the operating system keeps a record of its name and the exact location where its data is stored on the disk. When Jamal later wants to open a particular document, the operating system uses this record to find and retrieve the correct file, rather than Jamal needing to know exactly where on the physical disk its data is stored. [2 marks]: [1] for organising files into folders, [1] for keeping track of each file’s name/location so it can be found again.

Part (b): Security and user-account management

The operating system requires each person to log in using their own username and password, and it keeps track of which account is currently logged in. Access rights to files are linked to the account that owns them: files Jamal creates while logged in under his account are only accessible when Jamal is the one logged in. When Aisha logs in under her own, separate account, the operating system does not give her permission to open, edit or delete files that belong to Jamal’s account, even though both accounts are on the same shared laptop. [2 marks]: [1] for recognising that each user has a separate account with its own access rights, [1] for explaining that this is what prevents Aisha from opening/changing Jamal’s files under her own login.

Part (c): Protecting against data loss. Backup software

Backup software is the utility Jamal should use regularly. It makes a copy of his coursework files (or of the entire system) onto separate storage, such as an external hard disk, a USB drive or cloud storage, at regular intervals. If the laptop’s own hard disk later fails, or a file is accidentally deleted or corrupted, Jamal can use this separate copy to restore his coursework, rather than losing it permanently. [2 marks]: [1] for correctly identifying backup software, [1] for describing that it makes a separate copy of files that can be used to restore them if the originals are lost.

Part (d): Program libraries and DLLs

A program library is a collection of pre-written, tested subroutines (or routines/functions) that provide commonly needed functionality, such as drawing shapes on screen, which a programmer can call from within their own program instead of writing that code from scratch. Jamal calls the ready-made graphics routine, supplied as a DLL, because doing so saves him the time it would take to write and test his own circle-drawing code, and because the library routine has already been tested, so it is more likely to work correctly than new code he writes himself. A DLL specifically is a library file whose code is linked into a program only while that program is running, rather than being permanently copied into the program’s own file, and, because of this, the same DLL can potentially be shared by more than one running program at once. [2 marks]: [1] for a correct definition of a program library, [1] for a valid reason for using the ready-made routine (e.g. saves development time, or the code is already tested).

Final answers

(a) File management organises files into folders and tracks each file’s name/location so it can be found and retrieved.
(b) Access rights are linked to the specific logged-in user account, so Aisha’s account cannot open or change Jamal’s files.
(c) Backup software. Copies files to separate storage so they can be restored if the hard disk fails or files are lost.
(d) A program library is a collection of pre-written, tested routines a programmer can call instead of writing their own code; Jamal saves development time and gets already-tested code.