Flashcards
8: System Software
Cards in this deck (47)
- 1Operating SystemA software platform that provides facilities for programs to be run which are of benefit to a user.
-software to control hardware and interact with application software
-example of a system software
ie OS, utility ptrograms - 2Application softwareperform specific task for computer user - for user benefit
- 3What are some operating system activities? 8User-system interface
Program-hardware interface
Resource management
Memory Management
Device Management
File management
Security management
Error detection and recovery
(manages hardware and applications, creates UI, layer of security) - 4User-system interfaceallow user to get software and hardware to do something useful should provide: command-line interface
GUI - 5Program-hardware InterfaceOperating system ensure hardware does what software wants. Programmer doesn't need to know how hardware works
- 6Resource ManagementWhen program started to run described as a process - not able to run without interruption. Many process running at once - needs access to resources on computer system.
- 7ProcessA program that has begun execution
- 8Resource management aim: Achieve best possible efficiency 2 most important aspects are:- scheduling of processes
Resolution of conflicts when 2 processes requires same resource - 9Memory Management 3 important aspects:-Memory protection ensure 1 program doesn't try to use same memory location as another
-memory organisation scheme is chosen to achieve best usage of limited memory size ie virtual memory involving paging or segmentation
-memory usage optimisation involves about which processes should be in main memory and where stored in memory - 10Device management includes: 2-Installation of appropriate device driver software
-Control of usage by processes - 11File Management 3 main features are provision of:-File naming conventions
-Directory (folder) structures
-Access control mechanisms - 12Security Management aspects include: 3-Provision for recovery when data is lost
-Prevention of intrusion
-Ensuring data privacy - 13Error detection and recoveryErrors can arise in execution of a program either because it was badly written or has been supplied with inappropriate data. Other errors associated with devices not working correctly. OS should have capability to interrupt running process and provide error diagnostics. In extreme cases: shut down system without loss of data
- 14Utility ProgramCan be provided by os or installed separately. It is a program that is not executed as part of the normal running of the operating system. Instead it's a program that the user or the os can decide to run when needed. ie some utility programs manage hard disks.
- 15Utility Softwareanalyzes, configures, optimisms or maintains a system
- 16Hard disk formater and checker: a disk formatter will typically carry out: 3-Removing existing data from a disk that has been used previously
-Setting up the file system on the disk, based on a table of contents that allows a file recognized by the os to be associated with a specific physical part of the disk
-Partitioning the disk into logical drives if this is required - 17Another utility program, which can be a component of a disk formatter, performs disk contents analysis and if possible, disk repair when needed. Program first checks for errors on the disk. What are errors from?-Physical defect resulting in what called a 'bad sector'. Usually arise during manufacture or from mishandling of the system ie moving computer without ensuring the disk heads are secured away from disk surface.
-event ie loss of power or error causing sudden system shutdown. As a result some of the files stored on the disk may no longer be useable. - 18What can a disk repair utility program do?A disk repair utility program can mark bad sectors and ensure file system no longer tries to use them. When integrity of files has been affected, utility may be able to recover some of the data but otherwise has to delete files
- 19Hard disk defragmenter (can also be part of disk repair but not primarily concerned with errors) Disk will become less efficient due to constant creation, editing and deletion of files leaves them in fragmented state. What does defragmenter up do?A defragmenter utility program recognises file storage to return to a state where all files stored in one block across a sequence of sectors. For large disk - take time. Will be impossible if disk is too full due to lack of working space for rearrangement.
- 20Backup Software - what does a backup utility program do? 2Establish a schedule for backups
Only create a new backup file when there has been a change. - 21File Compression Utility programMinimizes hard disk storage requirements (compression is most important when transmitting data)
- 22Virus Checking programShould be installed as permanent facility to protect a computer system. There is a delay before a virus is recognised and further delay before virus checker been updated to deal with it - virus checker must be regularly updated and scan all files on a computer system as a matter of routine.
- 23'Programs' in a program library Advantages 3Usually subroutines to carryout particular tasks - can use these within own programs. Saves time and errors and trouble
- 24examples of library routinesexamples of library routines: built-in functions in programming languages, statistics processing availabe from Numerical Algorithms group (NAG) library
- 25Translation of source code simple overview with compilerIf compiler used for translation and no errors found, compiler produces object code (machine code). Code cannot be executed by itself. Instead has to be linked with code for any subroutines used by it. It possible to carry out the linking before loading hte full code into memory and running it
- 26Why is it a dis to linking library routines into the executable code?Every program using a routine has to have own copy - this increases storage space requirement for executable file. Also increases memory usage when more than one process uses the routine
- 27What is alternative instead of linking library routines to executable code?Use a routine from a dynamic linked library (DLL). What DLL routine available the executable code just requires a small piece of code to be included. Allows link to the routine, stored separately in memory, when execution of the program needs it. Many processes can be linked to the same routine.
- 28What are the advantages of using a dynamic linked library? 3Adv - less storage space for executable files for all programs.
Memory requirement also minimised.
If new version of routine available it can be loaded into memory so any program using it is automatically upgraded. - 29What are the disadvantages of using a DLLThe program is relying on the routine being available and performing expected function. If DLL becomes corrupted or a new version has bugs not yet discovered the program will fail or produce an erroneous result. The user running the program will find it difficult to establish what needs to be done to get the program to run without error.
- 30Compiler vs interpreter 3Compiler: produces object code, doesn't need data, executes all
Interpreter: executes line by line, needs data present, no object code - 31A file containing source code written in a high-level language what are the 8 steps for an interpreter?1. Interpreter program, the source code file and the data to be used by the source code program are all made available
2. Interpreter program begins execution
3. First line of the source code is read
4. Line is anaylsed
5. If error is found, reported and interpreter program halts execution
6. If no error found, line of source code is converted to an intermediate code
7. Interpreter program sues this intermediate code to execute required action
8. Next line of source code is read and steps 4-8 repeated - 32What are the 8 steps for a compiler?1. Compiler program and source code file are made available but no data needed
2. Compiler program begins execution
3. First line of source code read
4. Line is analysed
5. If error round this is recorder
6. If no error found line of source code is converted to an intermediate code
7. Next line of source code is read and steps 4-7 repeated
8. When whole of source code been dealt with one of the following happens:
- if no error found in whole source code the complete intermediate code is converted into object code
- if errors found a list of these is output and no object code produced - 33The advantages 1 and disadvantages 2 to programmer creating interpreted programs-Adv When a program is being developed as errors can be identified as occur and corrected immediately without having to wait for the whole of the source code to be read and analysed
-Dis During a particular execution of the program, pars of the code containing sintax errors may not be accessed so if errors are still present, not discovered until later
-Dis When a program error free and distributed to users because the source code has to be sent to each user - 34The advantages 1 to programmer creating compiler programsAdv - Executable file can be distributed to users so the users have no access to the source code
- 35The disadvantages 1 to user of interpreted programsInterpreter and source code have to be available each time an error-free program is run
- 36The advantages and disadvantages to user of interpreted programs 3Adv: Compiled object code will provide faster execution than is possible for an interpreted program
- only object code has to be available each time an error-free program is run
Dis: Compiled object code is less secure as it could contain a virus - 37note - where can a program be run with interpreter or compilerWhether an interpreter or a compiler is used, a program can only be run on a particular computer with a particular processor if the interpreter or compiler program has been written for that processor
- 38If option, interpreter justified when program being developed because: 3-one error in a program can lead to several other errors occurring
-An interpreter can detect and correct an early error so limiting subsequent ones
-debugging facilities provided in association with the interpreter speed this process - 39Choice of compiler justified when programmer is confident that the program is an near error-free as possible because: 3-Executable file can be created
-this can be distributed for general use
-Execution of the program will be faster than if an interpreter were used - 40Using programming language JavaEvery type of computer has to have java virtual machine created for it. When programmer writes a java program this is compiled first of all to create Java Byte Code. When program is run, this code is interpreted by the Java Virtual Machine. Java Byte Code can be transferred to any computer that has a java virtual machine installed.
- 41What are features found in atypical integrate development environment (IDE)? 5Prettyprinting
Context-sensitive prompts
Dynamic Syntax checks
Expanding and collapsing code blocks
Debugging - 42DebuggingFinding and correcting errors, often called 'bugs', in a program
- 43PrettyprintingPresentation of the program code typed into an editor ie pytonIDE automatically color-codes keywords, built-in functions calls, comments, strings... indentation is automatic
- 44Context-sensitive PromptsDisplays hints and available identifiers that may be appropriate at current intersection point of program code (ie type f comes up with for)
- 45Dynamic Syntax checksWhen a line been typed some editors perform syntax checks and alert programmer of errors ie squiggly line underneath
- 46Expanding and collapsing code blocksSaves excessive scrolling if can collapse blocks of statements(arrow)
- 47DebuggingIDE often comes with features to help with debugging. Possible to set a break point on a turned on debugger feature. Program will stop at breakpoint. Can then be stepped through, one instruction at a time
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- A Level AS Computer Science (Unit 1: Theory Fundamentals) Flashcards on 8: System Software, created by HRYN red on 02/01/2023.
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