Notes-for-CAIE

1.5 System software

1.5.1 Operating system

• describe why a computer system requires an operating system
• explain the key management tasks carried out by the operating system

File management

w18 12 Q1 [3]

• Spaces allocated to particular files
• Maintains directory structures
• Provides file naming conversions
• Control access

Printer management

w18 12 Q1 [3]

• Installs printer driver
• Sends data to the printer
• Sends command to the printer
• Receives error messages from the printer

Memory management

w18 11 s18 11 Q3 [3]

• Allocates RAM to programs
• Keep track of allocated and free memory locations
• Swaps data to and from the hardware
• Handles virtual memory
• Paging

Security management

w18 11 s18 11 Q3 [3]

• Set up user accounts
• Authentication
• Implements access rights
• Automatic backup
• System roll back

Process management

w19 11 [3]

• Manage the scheduling of the processes,
• … allows multi-tasking
• Manage the resources needed by the processes
• Enable processes to share information
• Prevents interference between processes

Provision of a UI

• Allows a user to communicate with the hardware
• Provides facility for user inputting data
• Provides facility for outputting to the user
• By example: GUI, CLI

1.5.2 Utility programs

• show an understanding of the need for typical utility software used by a PC computer system:
  • disk formatter
  • virus checker
  • defragmenter software
  • disk contents analysis/disk repair software
  • file compression
  • backup software

Virus checker [2]

• Set up a schedule for virus-checking
• Isolate viruses
• Scans files stored on a computer system

Backup software [2]

• Create a copy of the contents of a disk automatically or manually
• Allow users to decide what is backed up.
• May encrypt the backup files
• Restores data if necessary

Disk repair software [3]

• Checks [1] and resolves [1] for any errors on the disk
• Marks bad sectors on the disk
• Retrieves files from a damaged disk

Firewall

File compression

Defragmentation

1.5.3 Library programs

• show an understanding that software under development is often constructed using existing code from program libraries
• describe the benefits to the developer of software constructed using library files, including Dynamic Link Library (DLL) files
• draw on experience of the writing of programs which include library routines

DLL

w16 11 Q2 [2]

• A DLL file is a shared library file
• Code is saved separately from the main .EXE files
• Code is only loaded into main memory when required at run-time
• The DLL file can be made available to several applications (at the same time)

Benefits of using libraries [4]

• Saves time
• … as he don’t have to write some routines
• Program library routines should already be test
• … so he can use without testing
• Program library routines may provide complex tasks
• … he won’t have to work out how to code them

1.5.4 Language translations

• show an understanding of the need for:
  • assembler software for the translation of an assembly language program
  • a compiler for the translation of a high-level language program
  • an interpreter for execution of a high-level language program
• explain the benefits and drawbacks of using either a compiler or interpreter
• show awareness that high-level language programs may be partially compiled and partially interpreted, such as Java