U5 System Software

Question 1

Why is the OS needed?

Answer 1

• Programs to run on background of computer system
• Controls operation of computer system
• Provides a user interface
• Controls hardware communication
• Provides environment where application software can be executed

Question 2

What does memory management involve?

Answer 2

• memory protection to ensure 2 programs do not try to use same memory space
• Paging
• Use of virtual memory

Question 3

What does file management involve?

Answer 3

→ Provides file naming conventions
→ Maintains a directory structure
→ Allocates space to particular files

Question 4

What does security management involve?

Answer 4

→ Proves usernames and passwords
→ Ensures data privacy
→ Prevents unauthorised access
→ Carries out automatic backup

Question 5

What does hardware management involve?

Answer 5

→ Installation of appropriate driver software
→ Controls access to data sent to and from peripheral devices
→ Receives and handles interrupts from hardware devices

Question 6

What does process management involve?

Answer 6

→ Enables multiprogramming and multitasking
→ Manages scheduling of processes
→ Manages which resources processes require such as allocating memory
→ Handles process queue

Question 7

What does a disk formatter do?

Answer 7

→ Prepares a hard disk to allow data to be stored on it
→ Deletes any existing data on disk
→ Performs formatting process where computer ‘draws lines’ on disk surface to split it into small areas

Question 8

What does a virus checker do?

Answer 8

→ Anti-virus checks all files before they are run or loaded on your computer
→ It compares possible viruses to a database of known viruses
→ Also does heuristic checking that checks for suspicious behavior that could indicate a virus - this could be useful as it could be a virus which is not yet on the database
→ It will put a suspected virus on a quarantine and a signature will be sent to the anti-virus company to inspect
→ Computers will then get a software update with the new virus database

Question 9

What does defragmentation software do?

Answer 9

Files get written onto disk surface in scattered locations and take long time for read head to access them.
Defrag software used to place them in contiguous location so they can be accessed by read head quickly
Also frees contiguous space for new files

Question 10

What does disk content analysis/disk repair software do?

Answer 10

• Allows visualisation of disk space usage
• Gets sizes of folder and files
• Allows disk to report errors
• Software attempts to offer solution

Question 11

What does file compression software do?

Answer 11

• Reduces file size by removing redundant data in files
• Makes files take up less storage
• Faster transfer of data - quicker download/upload times

Question 12

What does backup software do?

Answer 12

• Makes copy of files on another storage medium
• Allows scheduling backups
• Gives ability to give restore point

Question 13

What are program libraries?

Answer 13

Pre-written subroutines that can be called in other programs by installing the library

Question 14

Different between static and dynamic libraries

Answer 14

Static libraries compiled into executable file at compile time
Dynamic libraries loaded at runtime, enabling resource sharing among multiple programs

Question 15

What are benefits of program libraries?

Answer 15

• Saves time: Less code needs to be written
• Smaller testing time: Pre-tested and used by others
• Library file is a complex algorithm which user doesn’t need to understand to use

Question 16

What are DLL files?

Answer 16

• Shared library file that contains code and data

Question 17

Benefits of DLL files

Answer 17

• Code only loaded once which reduces memory requirements
• DLL made available to several applications simultaneously, reducing strain on memory
• DLL files act as modules in more complex programs, easier to install and run updates
• Maintenance doesn’t have to be done by programmer because DLL separate from program

Question 18

What is an assembler?

Answer 18

Software than translates assembly language statements into machine code for execution

Question 19

Features of a compiler

Answer 19

• Translates a full high-level program to machine code
• Creates .EXE file
• Faster execution time
• Reports errors at end of compilation. Difficult to locate errors.
• Only produced when all errors fixed
• Used when development completed

Question 20

Features of a interpreter

Answer 20

• Translates and executes high level languages one line at a time
• No file produced
• Slow execution time as each line translated and run
• Debugging easier and in real-time because program stops when error reached
• Program can be run anytime, even code not finished
• Used while developing

Question 21

Two-step translation

Answer 21

• Partially compiled, partially interpreted
• Java code first translated to bytecode by Java Compiler
• Bytecode finally interpreted by Java virtual machine to produce machine code

Question 22

What are context-sensitive prompts?

Answer 22

Displays choice of keywords and identifiers appropriate and allows user to select

Question 23

What are dynamic syntax checks?

Answer 23

Automatic checking and highlighting of syntax errors, as line it typed

Question 24

What is PrettyPrint?

Answer 24

Automatic indentation and colour-coding of keywords

Question 25

What are expand and collapse code blocks?

Answer 25

Saves excessive scrolling and easy to see global variable declarations and main program body

Question 26

What is single-stepping?

Answer 26

Executes program line-by-line so values can be checked

Question 27

What are breakpoints?

Answer 27

Stops program at a specific line to ensure program operates correctly up to a line