Chapter 5 - System Software Flashcards
CMOS
Complimentary metal-oxide semi-conductor
BIOS configuration stored here, meaning it can be altered/deleted as required
Operating system
Software that provides an environment in which applications can run and provides an interface between hardware and human operators
HCI
Human-Computer Interface
GUI
Graphical User Interface
CLI
Command Line interface
Icon
Small picture/symbol used to represent an application on a screen
WIMP
Windows, Icons, Menu and Pointing device
One of the first commonly used GUI environments
Developed for use on PCs
Post-WIMP
Interfaces that go beyond WIMP and use tough screen technology rather than a pointing device
Memory management
Part of the operating system that controls the main memory
Memory optimisation
Function of memory management that determines how memory is allocated and deallocated
Memory organisation
Function of memory management that determines how much memory is allocated to a location
Security management
Part of the operating system that ensures the integrity, confidentiality and availability of data
Virtual memory systems
Memory management (part of OS) that makes use of hardware + software to enable a computer to compensate for shortage of actual physical memory
Memory protection
Function of memory management that ensures 2 competing applications can’t use same memory locations at the same time
Process management
Part of OS that involves allocation of resources and permits the sharing and exchange of data. Thus allowing all processes to be fully synchronised
Hardware management
Part of OS that controls all input/output devices connected to a computer (made up of sub-management systems such as printer management, secondary storage management etc.)
Device driver
Software that communicates with the OS and translates data into a format understood by the device
Utility program
Parts of the OS which carry out certain functions, such as virus checking, defragmentation or hard disk formatting
Disk formatter
Utility that prepares a disk to allow data/files to be stored and retrieved
Bad sector
Faulty sector on an HDD which can be soft or hard
Anti virus software
Software that quarantines and deletes files/programs infected by malware. It can run in the background or be initiated by the user
Heuristic checking
Checking of software for behaviour that could indicate a possible virus
Quarantine
File/program identified as being infected by a virus which has been isolated by anti-virus software before it is deleted at a later stage
False positive
File/program identified by a virus checker as being infected but the user knows this cannot be correct
Disk defragmenter
Utility that reorganises the sectors on a hard disk so that files can be stored in contiguous data blocks
Disk content analysis software
Utility that checks disk drivers for empty space and disk usage by reviving files and folders
Data compression
Software that compresses data before storage on an HDD
Back-up utility
Software that makes copies of files on another portable storage device
Program library
Library on a computer where programs and routines are stored which can be freely accessed by other software developers for use in their own programs
Library program
Program stored in a library for future use by other programmers
Library routine
A tested and ready-to-use routine available in the development system of a programming language that can be incorporated into a program
DLL
Dynamic Link file
Library routine that can be linked to another program at the run time stage
Translator
Systems software used to translate a source program written in any language other than machine code
Why computers need an operating system (5)
A set of programs designed to run in the background on a computer system which:
Controls operation of computer system
Provides a user interface
Controls how computer responds to user’s requests
Controls how hardware communicate
Provides an environment in which application software can be executed
Storage of BIOS
Configuration stored in CMOS memory meaning it can be deleted or altered as required
RAM + operating system
Only part of the OS is copied into the RAM since the computer’s performance would be affected if the whole thing was loaded at once
Common OS examples (4)
Microsoft Windows
Apple Mac OS
Google Android
IOS
How HCI is achieved
Through GUI or CLI if the user wishes to directly communicate with the computer
Disadvantages of CLI (3)
Command Line Interface
Requires a user to type instructions to choose options from menus, open software etc.
User has to learn a number of commands to carry out basic operations
Takes time to key in commands every time an operation has to be carried out
Advantages of CLI (2)
The user is in direct communication with the computer
Not restricted to a number of pre-determined options
Advantage of GUI
It allows the user to interact with a computer using pictures or symbols, meaning a whole line of CLI code can be replaced by a single icon
Windows manager
Looks after interaction between windows, the application and the windowing system which handles the pointing devices and the cursor’s position
Operating system tasks (5)
Memory management
Security management
Process management
File management
Hardware management
Memory management partitions (3)
Memory protection
Memory optimisation
Memory organisation
Memory optimisation (4)
Used to determine how computer memory is allocated + de allocated when a number of applications are running simultaneously.
Determines where the applications are stored in the memory
Keeps track of all allocated + free memory available for use
Swaps data to and from HDD/SSD to maintain optimisation
Memory organisation
Determines how much memory is allocated to application and how the memory can be split up most appropriate/efficiently
How can memory organisation be done (4)
Single (contiguous) action-all memory made available to single application. Used by MS-DOS + embedded systems
Partitioned allocation- memory split up into contiguous blocks then memory management allocates a partition to applications
Paged memory - similar to partitioned, but each partitioned is a fixed size. Used by virtual memory systems
Segmented memory- memory blocks not contiguous, each segment is a logical grouping of data
Memory protection
Ensures 2 competing computers can’t use the same memory locations at the same time. Otherwise data could be lost, incorrect results produced, security issues or a computer crash.
Why must memory protection always be apart of any type of memory organisation used
To prevent 2 applications from occupying the same part of memory
How to achieve security management (7)
Carry out OS updates as they become available
Ensure anti-virus software is up to date
Communicate with firewall to check computer traffic
Maintain access rights for all users
Offer ability to recover lost/corrupted data
Prevent illegal intrusion to computer system
Functions of hardware management (3)
Communicate with all input + output systems using device drivers
Translate data from file to format the input/output device can understand using device drivers
Ensure each hardware resource has priority so it can be used and released as required
Actions of printer management (5)
Locates + loads printer driver into memory
Sends data to printer buffer ready for printing
Sends data to printer queue
Sends control commands to printer throughout printing process
Receives + handles error messages + interrupts from the printer
Main tasks of file management (6)
Defining file naming conventions
Performing specific tasks, open, close etc.
Maintaining directory structures
Ensure access control mechanisms are maintained
Specify logical file storage format
Ensuring memory allocation for a file be reading it from the HDD/SSD and loading it into memory
Utility software offered by most OS (6)
Hard disk fragmenter
Virus checker
Defragmentation software
Disk contents analysis/repair
File compression
Back up software3
Hard bad sectors (3)
(Difficult to repair)
Caused by manufacturing errors
Damage to disk surface caused by allowing read-write head to touch the disk surface
System crash could damage disk surface
Soft bad sectors (2)
Sudden loss of power leading to data corruption in some of the sectors
Effect of static electricity leading to corruption of data in some sectors in Hard disk surfaces
What back-up utility does (2)
Allow backing up schedule to be made
Only carry out backup procedure if changes have been made to a file
Versions of a file for total security (3)
Current stored on internal HDD
Locally backed up copy on portable SSD eg.
Remote back-up version
Function of a hard disk formatter (4)
New hard disk drive needs to be initialised ready for formatting
Organises storage space by assigning it to data blocks (partitions - contiguous blocks of data)
Writes files which holds directory data and tables of contents at the beginning of each partition - allows the OS to recognise a file to find it on the disk surface
Do carry out tests on each sector of the hard disk.
Carrying out full formatting using NTFS
All disk sectors are filled with zeros which are read back thus testing the sector but losing any data already stored there.
What happens when you reformat an HDD which has already been used
Data is lost during the formatting procedure
Repairing a faulty disk
If bad sectors are discovered the sectors are flagged as bad and the file tracking records are reorganised by replacing bad sectors with new, unused sectors. A Damaged file will now contain an ‘empty’ sector which allows the file to be read but it will be corrupted since the bad sector will have contained important data. It is important to delete damaged files for the rest of the HDD to be effectively repaired.
Features of antivirus software (4)
Check software/files before they are run/loaded on a computer
Compare possible viruses against a database of known viruses
Carry out heuristic checking
Put possibly infected files into quarantine to automatically delete the virus or let the user identify a false positive
Why defragmentation software is important
Without it as the HDD becomes full files become scattered all over the disk surface as they are deleted, partially deleted, extended etc. This leads to slower data access time and the HDD read-write head requiring several movements to find data.
Function of back-up utility (2)
Allows a schedule for backing up files to be made
Only carry out a back-up -to édite if there haven’t been any changes made to a file
When are program libraries used (2)
When software is under development and the programmer can utilise pre-written sub-routines in their own programs, saving considerable development time
To help a software developer who wishes to use DLL subroutines in their own programs, so they must be available at run time
Benefits of using programming libraries (5)
Removes the need to rewrite the routines every single time (saves time + cost)
Leads to modular programming which means several programmers can work on the same software simultaneously
Allows continuity with other games that form part of a range
Allows maintenance of a ‘corporate’ image in all software being developed by a particular company
Saves development time testing each routine since routines are tested and(should be)error free
Static library
Software being developed is linked to executable code in the library at the time of compilation. Library routines would be embedded directly into the new program code
Pros of using DLL files (4)
Executable code of main program is much smaller since DLL files are only loaded into memory at run time
Possible to make changes to DLL files independently of the main program and it will not be necessary to recompile the main program
Can be made available to a number of applications at the same time
Memory and execution time is saved
Cons of using DLL files (4)
Executable code is not self contained, so all DLL files need to be available at runtime time to prevent software crashes and error messages
Any DLL linking software in main program needs to be available at run time to allow links with DLL file to be made
If any DLL files have been changed it could lead to unexpected results or crashing of the main program
Malicious changes to files due to Malware could be a threat to the main program through the linking process
Translator
System software used to translate a source program written in any language other than machine code
Compiler
Computer program that translates a source written program in a HLL to machine code or p-code, object code
Interpreter
Computer program that analyses and executes a program written in HLL line by line
Pretty printing
Practice of displaying or printing well set out and formatted source code, making it easier to read and understand
IDE
Integrated Development Environment
Suite of programs used to write and test a computer program written in HLL
Syntax error
Error in the grammar of a source program
Logic error
Error in the logic of a program
Debugging
Process of finding logic errors in a program by running or tracing the program
Single stepping
Practice of running a program one line/instruction at a time
Breakpoint
Deliberate pause in the execution of a program during testing so that the contents of variables, registers etc. can be inspected to aid debugging
Translators (3)
Assemblers
Interpreters
Compilers
Assembler (4)
Source program written in assembly language
Machine dependent
Object program generated and stored on disk (needs a loader program) or in main memory
Each line of source code program generates one machine code instruction,one to one translation
Compiler (4)
Source program written in HLL
Not machine dependent
Object program generated and stored on a disk/in main memory
Each line of source program generates many machine code instructions, instruction explosion
Interpreter (4)
Source program written in HLL
Not machine dependent
No object program generated, instructions are executed under the control of the interpreter
Each line of source program generates many machine code instructions, instruction explosion
Pros of compilers (5)
End user only needs the executable code, so no need to purchase a compiler to translate
Developer keeps hold of source code so they can charge for upgrades and alterations
Compiled programs have no syntax or semantic errors
Source program can be translated on one type of computer and executed on another
Compiled programs are a hucher to execute as translation has been compiled and machine code may already have been optimised
Cons of interpreter (5)
End user needs to purchase a compiler/interpreter to translate source code before use
Developer relinquishes control of source code and can’t charge and could have intellectual property used.
Interpreted programs can’t be interpreted on one type of computer and executed on another
Interpreted programs still contain syntax/semantic errors which need to be debugged.
Interpreted program takes longer to execute since each line needs to be translated
Cons of compilers (4)
Untested programs may cause computer to crash
End users don’t have access to source code + run time libraries so are reliant on developer
During development, special routines are needed to view partial results
Finds all errors in a program, one error detected means computer finds other dependent errors. More errors found than the actual number
Pros of interpreters (4)
Untested programs should not cause computer to crash
Partial results can be viewed during development
If program is purchased, end users have all source code and libraries enabling modification
Easier to develop and debug as errors can be corrected on each line
Partial compiling and interpreting
Achieves shorted execution times by source code being checked and translated by a compiler into object code which is now a low level machine independent code called intermediate code, p-code or bytecode. To execute the program, the object code can be interpreter]d by an interpreter or compile day a compiler
Features of IDEs (4)
Source code editor
Compiler, interpreter, or both
Run-time environment with a debugger
Auto documenter
Source code editor
Allows a program to be written and edited without the need to use separate text files. It speeds up the development process as editing can be done without changing to a different piece of software each time the program needs correcting or adding to. Most offer pretty printing. Some offer time sensitive prompts with text completion and provide dynamic syntax checking
Dynamic syntax checking
Finds possible syntax errors as the program code is being typed im
Auto documenter
Explains the function and purpose of programming code
Run time environment with a debugger
Program that runs the program under development and aids the process of debugging. It allows the programmer to single step through the program one line at a time or to set a breakpoint to stop the execution at a certain point. A report window shows the contents of the variable and expressions evaluated at that point in the program allowing the programmer to see if the program works as intended
