cs Flashcards
What is Compression in Utility Software
Compression reduces the size of a file so that it takes up less space and downloads faster over the internet
What needs to happen before a compressed file can be read
needs to be extracted first
What happens when a file is compressed
the data may be lost or quality is reduced (e.g image or audio file)
it may be presented in a different way using binary, it will retain the original data but compressed in a different format
What is disk fragmentation in Utility software
a program that reorganises files on a hard disk, putting fragments of files and free space back together
What is the advantage of disk defragmentation
reading and writing times are quicker which speeds up the access of files as they are not stored in different parts of memory because of fragmentation when a hard disk become full
Why shouldn’t a solid-state drives not be fragmentation
They have no moving parts. it is unnecessary and also reduces the drives’s lifespan .
Example of anti-malware in utility software and what it does
Antivirus checker checks hard drive as its responsible for detecting potential threats to the computer by comparing files to know virus definitions alerting the user and removing these threats
What is anti-malware in utility software
software helps keep your computer and files safe from different types of malware.
what does thea utomatic updating in Utility software do
This utility ensures the operating system is kept up to date, with any updates being automatically installed when the computer is restarted.
What does automatic updating tackle
Updates tackle bugs or security flaws so this ensures the system is less vulnerable to malware and hacking threats.
What does backup in utility software do
The backup utility automatically creates routine copies of specific files selected by the user
What type of routines could backup be specified by the user?
When: the user wants the files to be backed up, they may specify by requesting automatic or selecting a desired schedule
Where: the destination in which they are stored
what : it wants to back up
Why are back ups beneficial in software utility
In the event of a power failure, malicious attack or other accident files can be recovered
Why is updating important in utility software
new viruses and threats are constantly being devised and discovered
Why is application software needed to be updated in utility software
improvement and bug fixes may be provided
types of malware
viruses
trojans
worms
spyware
Note about back up software
it comes with operating system but can also be purchased separately (e.g apps )
what are utility softwares designed for
keep computer safe
keep it running efficiently
provide with useful tools to manage files and applications
What does open/ closed source softwares mean?
this refers wether or not the source code is accessible to the public
What is a source code ?
source code is Witten by a programmer and refers to object code before it has been compiled.
Define open source software
Open source code can be used by anyone without a license and is distributed with the source code.
define close source software
Closed source code requires the user to hold an appropriate license to use it. Users cannot access the source code as the company owns the copyright license.
Advantages of open source software
Can be modified and improved by anyone
Technical support from online community
Can be modified and sold on
Disadvantage of open source
Support available online may be insufficient or incorrect. No user manuals.
Lower security as may not be developed in a controlled environment
Disadvantages of closed source software
restrictions on how the software can be used
Users cannot modify and improve software themselves
License restricts how many people can use the software at once
Advantages of closed source software
High levels of security as developed professionally.
Company owning software provides expert support and user manuals
Thorough, regular and well-tested updates
How may a user choose wether to used open source or closed software?
depends on the sustainability of the software to the task they will be using it for
costs: implementation, maintenance, training of staff , licence
Functionality: feature available, ease of use
How may a user choose wether to used open source or closed software?
depends on the sustainability of the software to the task they will be using it for
costs: implementation, maintenance, training of staff , licence
Functionality: feature available, ease of use
How may a user choose an application?
Functionality: if it does what the user wants
hardware: does it run on the available hardware
Availability:is it available off the shelf or does it need to be bespoke (specially written)
cost: how much will it cost
Reliability: has it been tested, well used and are there any bugs.
define freeware software
Software that is free and anyone can use but the source code is not available
advantages to users of using open source software
- software is free
wide community modification
users can modify software to suit their needs
Disadvantage to users of open source software
can be poorly supported
some feature might not be well tested
Advantages to creators of open source software
gets their software out there to a wide community
-improvements: anyone can help find security holes
Disadvantage to creators of open source software
-little-to-no financial gain
users may cause malware on system
advantage to users of closed source software
well supported, tested and professional built product
reduces risk of other users stealing their work
Advantage to user of using closed Source software
- cost or ongoing subscription fee
Advantages to creators of closed source software
they receive an income for their product
Disadvantage to creators of closed source software
constant demand from community for more features and improvements
privacy issues
Who protects closed source software
copyright design and patents act
example of open source software
Linux and open office
3 types of translators
interpreters
compilers
assemblers
what is a translator ?
program that converts high-level source code into low level object code, which Is then ready to be executed by a computer
define high-level code
code that is written and understood by the programmer but not the computers e.g Python, java
what is low level code / language
languages that sit close to the computer’s instruction set . An instruction set is the set of instructions that the processor understands
very close to writing actual machine instructions
object code is the same as ….
machine cose
what is compiler
translates high-level code into machine code all at once, after carrying out a number of checks and reporting back any errors.
define machine code
executable binary code produced by a compiler, interpreter or assembler
example of machine code
1001000100010001000
this type of code is what the cpu understand and will execute its corresponding instruction
what is assembly code translated by
assembler
2 types of low level language
assembly language
machine code
what happens if changes need to be made in during compiling process
the whole program must be recompiled
Important thing about compiler
once code has been compiled to produce machine code, it can only be executed on certain devices.
a compiled code is specific to a particular processor type and operating system
in compilers do translators need to be present
code can run without a translator being present
what is an interpreter
translates and execute code line by line (from high level language to machine code )if there are no syntax errors
differences between interpreter and compiler
Initially interpreter appear faster than compilers as code is instantly executed, but slower than running compiled code as code must be translated each time it is executed within an interpreter
is an interpreter platform dependent?
it is platform independent however it must have the correct interpreter required to run on different platforms
what are interpreter useful for
testing code and pinpointing errors as time is not wasted compiling the entire program, before it has been fully debugged.
what does interpreted code require
requires an interpreter to tun on different devices. However the code ca be executed on a range of platforms as long as the right interpreter is available which makes the interpreted code more portable
who translates assembly code
assembler
what are interpreters useful for
coding ad debugging process as the program,mer does not have to wait for the entire program to compile: the interpreter will atop at a line if it fits an error
How does is assembly code translated
translated by the assembler which takes the nemonic of assembly code an stranslates them in a one to one relationship directly to machine code which can be executed on a specific processor architecture.
how can high level language be translated
compiler
or interpreter
define assembly code
a low level language that uses mnemonic to or single words represent to represent instructions
define assembler
program that converts assembly code in to machine code
what are assembly codes equivalent to
Each line of assembly code is equivalent to almost one line of machine code so code is translated on almost a one-to-one basis.
describe the process in which source code is translating using a compiler as a translator
- it takes the source code in its entirety
2.translates it and if successful it produces the machine code output
3.linker program provides any additional libraires needed
4a or 4b (one of the 2 could happen)
4a. the translated machine code will be immediately executed
4b. additional intermediate state could be created (called intermediate code) and may be further interpreted to tu turn into and run final machine code
describe the process in which source code is translating using an interpreter as a translator
an interpreter takes on line of source code translates it and executes it (becomes binary code) however stopping and produce error (syntax error) is a line of code contains an error
when there are errors in the code what does the compiler do
error is presented and won’t run unless all the errors in the code are corrected first
when there is an error in code what does the interpreter do
program partially executes, but error must be corrected on the line/lines told where the error are and run the program again
difference between machine code and binary code
they are the same binary code is suggests the numbers it comes with machine code e.g 100010001111010101
list the stages of compilation
s1.lexical analysis
s2.syntax analysis
s3.code genration
s4. code optimisation
Advantages of Assembler
programs written in machine language can bebe replaced by mnemonics which are easier to remember
memory efficient
speed of execute is faster
hardware oriented
requires fewer instruction to accomplish the same result
object code produced by a compiler can be distributed or executed without having a compiler present
Disadvantage of assembler
long programs written in such languages cannot be executed on small computers
takes along time to code or wirier the program (has more complex nature)
Advantages og compiler
object code produced by a compiler can be distributed or executed without having a compiler present (i.e no need for translation at run time )
speed of execute is faster than compiler
object code is more secure as it cannot be read without a great deal of reverse engineering
original source code is kept secret
Advantages of interpreters
1, platform independence - the source code can be run. on any machine which has the appropriate interpreter available
2, useful for program development as there is no need for lengthy recompilation each time a error is discovered
3, easy to write source code as the programs will always run stopping when it fid a syntax error
no recompiling when code is changed
Disadvantage of interpreters
program may run slower because each statement has to be translated to line by line
so if 10 statement is performed 20 times, all 10 and interpreted 20 times
code is not optimised
source code is required
when should compilers be used
on programs with occasional change
what happes in the lexical analysis stage
dont look a level
whitespace and comments are removed from the code.
functions of lexical analysis
dont look a level
- remove superfluous spaces
2,all comments, identified (eg hashtag or //) are removed - performs some simple error checking via lexical analyser
4.tokens are used to replace keywords, constant, identifiers ,e.g variable, found in source code
what are tokens
dont look a level
unique symbols (), {},+,=,A,B
what is a symbol table
dont look a level
where information about the token associated with each keyboard are stored
list the different software development methodology
waterfall lifecycle
agile methodology
extreme programming
spiral model
rapid application development
what is software development lifecycle
the number of district phases a programmer goes through when developing a solution for a computer system
stages of the software life cycle
feasibility : is the problem solvable
requirements: working out what the solution needs to do
analysis and design: working out how the solution needs to do it
Implementation: coding the solution
testing:checking it actually works
deployment: installing it in the target environment
evolution : checking I with the user- is the solution complete
maintenance: ensuring it continues to function properly
describe the waterfall model
software development methodology that is based on series of stages which are completed in sequence (once must be completed before the next is begun), from start to finish.
stages of the waterfall model
- Analysis (may also include feasibility using TELOS)
- design
- Implementation
- Evaluation
5.maintenance
Disadvantages of waterfall model
- inflexible: of changes are required within the process of development then programmers must revisit all levels again
unsuitable for projects with changing requirements
clients: little input after the specific document is agrees, client only involved at the beginning (analysis ) and at the end (evaluation ) of cycle= risk of dissatisfaction and small feedback , may be too late to Make changes
what’s TELOS
factors that should be evaluated in analysis stage before project is begun
List TELOS meaning
- Technical: is the project possible considering the technology available and accessible
- Economic: can the project be financed in the short-term and the long-term?
- Legal: can the project be solved within the law?
- Operational: can the project be successfully implemented and maintained?
- Scheduling: can the project be completed given the time available?
when to use waterfall model
- the requirements are very clear and fixed
no ambiguity in requirements
Technology is well understood
the project is short
what is a spiral model
a risk-driven methodology which allows its 4 stages to be passed repeatedly in the software project
aim of agile methodology
aim to improve the flexibility of software development and adapt to changes in user requirements faster
what happens in the loops in agile model
each successesive loop around the spiral generates a new more refined prototype until the software meets all the requirements.
stages of the spiral model
- analysis (system requirements)
design
implements (testing and development)
Evaluate (feedback to inform next iteration)
advantages of spiral model
- sofware produced at an early stage so problems and issues can be identifies early
- th user gives feedback and each prototype and any required changes can be ,Ade early in the process
the end result is more likely to be what the user wants
well define steps to are the project easy to. manage
Disadvantage of spiral model
time consuming: the process of developing prototypes, getting feedback and refining the prototypes takes time which may take the finished product longer to develop
- more costly because of the time involved (keep making improvements )
- not suitable for smaller projects
when to use the spiral model
medium to high risk projects
when users are unsure of their needs and what the possibilities are
when requirements are complex
large projects where a long time is requirement is needed and new technology may develop and significant changes occur
high budget
what is the agile model
a collection of methodologies which aim to improve the flexibility of software development and adapt to changes in user requirements faster.
note about agile / spiral model
less of a focus on documentation and more priority is given to user satisfaction.
Advantages of agile model
advantage of agile model
- customer satisfaction (continues feedbacks, input )
software easily dappled to changing circumstances
Flexible to changing: even late changed can be implemented
Produces high quality code
disadvantage of agile model
Poor documentation: lack of emphasis on design and documentation
project can fail to deliver if the customer is not clear about the final outcome
not suitable for noice programmer (new): experienced are better are making better decisions
- Requires consistent interaction
between user and programme
when to use agile model
when new changes need to be implemented:small incremental changes can be made frequently and for little cost
business expansion: business where users needs are constant changing an developing
what is extreme programming in software development
t utilises the Agile Software Development Methodology. XP is intended to improve the software quality and mainly the responsiveness to changing client requirements.
aim of extreme programming in software development
he aim of paired programming is to produce high-quality code, as the code is written by one person and critiqued by the other so is improved as it is written. Programmers work no longer than forty hours a week with the aim that quality is not compromised
how is the model built
using ‘user stories
Advantages of extreme programming
- Produces high quality code
- Constant user involvement means high usability
disadvantage
High cost of two people working on one project
- Teamwork is essential
- End-user may not be able to be present
uses of extreme programming
Small to medium projects with unclear initial requirements requiring excellent usability.
what is a rapid application development
an interactive methodology which uses partially functioning prototypes which are continually built -upon.
in RAD how are user requirements gathered
initially gathered using focus groups and used to develop an incomplete version of the solution which is given to the users to trial
in RAD how is the softare improved
user feedback is used generate the next, improved prototype until the prototypematches the requirements of the end -users at which point it becomes the final products
uses of RAD (rapid application development)
commonly used where user requirements are incomplete or unclear at the Start
Small to medium, low-budget projects with short time-frames.
advantages of RAD
Caters to changing user requirements
- Highly usable finished product
- Focus on core features, reducing development time
Disadvantage of RAD
Poorer quality documentation
- Fast pace may
reduce code quality (inefficient)t: continuos changes
types of testing in software development
advantages of waterfall model
Straightforward to manage
- Clearly documented
simplicity
easy to see if a project is running to schedule
different types of test strategies
- black box
- white box
-beta testing
alpha
what is black box testing
This is a form of testing where the software is tested without the testers being aware of the internal structure it aims to tests whether an input produces the expected output within the software
what is white box testing
This is a form of testing carried out by software development teams in which the test plan is based on the internal structure of the program( code logic).it involves testing the algorithms in the code an d making sure all parts of this algorithms function as intended
one thing to note about white box testing
All of the possible routes of execution through the program are tested.(and compared with other runs)
what is alpha testing
Alpha testing is carried out in-house by the software development teams within the company.reveal errors and bugs a re pinpointed and fixed
what is beta testing
used in commercial software development (MS. windows,MS word), it is carried out by end-users after alpha testing has been completed. Feedback from users is used to inform the next stage of development.
in a SDLC what are things to consider in analysis stage
Stakeholders state what they require from the finished product
Considering types of data involved including inputs, outputs, stored data and amount of data
(use interviews, questions, observation, documentation)
create system specification (user requirements)
what is a system specification document
document defines what the system will do but not how it will do it
used to create design and evaluate finished product
in a SDLC what are things to consider in design stage
Inputs: volume, methods, frequency
- Outputs: volume, methods, frequency
- Security features: level required, access levels
- Hardware set-up: compatibility
- User interface: menus, accessibility, navigation
test plan may also be designed at this stage.
in a SDLC what are things to consider in implementation stage
coding and testing software
making the software
writing technical documentation ()how it works
installed onto the users’ systems.
in a SDLC what are things to consider in evaluation stage
effectiveness of the software is evaluated against the system requirements defined at the analysis stage to evaluate its suitability in solving the problem. Different criteria are considered, including robustness, reliability, portability and maintainability.
Maintenance stage in a SDLC what are things to consider
Any errors or improvements that could be made to the software are flagged up by the end-users
Programmers will regularly send out software updates to fix any bugs, security issues or make any needed improvements.
