1.2.

3 INTRODUCTION TO PROGRAMMING

Procedural programming uses a sequence of instructions which may be

contained within in broken down procedures-carried out sequentially

STRUCTURED PROGRAMMING-uses the three main programming

structures sequence, selection and iteration

SEQUENCEcode is executed line by line from top to bottom

SELECTIONa certain block of code is run if a certain condition is met

using an if ,else if, else statement

ITERATIONa block of code is executed a certain number of times or while

a condition is met using for, while or repeat until loops

VARIABLEnamed locations in memory where data is stored

The contents of this location can be changed while the program is being
executed

CONSTANTnamed locations in memory but the value of this cannot be

edited by the program during execution, helps prevent accidental changes

PROCEDUREnamed block of code that performs a specific task that does

not return a value

FUNCTIONnamed block of code that performs a specific task that does

return a value

2**4 exponentiation ,2 to the power 4

DIV integer division

MODremainder

stringname.substring(0,5) takes characters 0,1,2,3,4

FILE HANDLING

myFile= openRead(“filename,txt”) opens a file TO READ IT

fileContent=myFile.readLine() reads a line from a file

myFile.close()to close a file

myFile=openWrite(“nameofffile.txt”)open a file to WRITE TO IT

myFile.writeLine(“Physics and Maths Tutor”)to write this line to a file

endOfFile()the end of file is given by this it checks if the file has no more
lines to read

READING A FULL FILE PSEUDOCODE

myFile=openRead(“data.txt”)

WHILE NOT endOfFile(myFile)

line = myFile.readLine()

OUTPUT line

ENDWHILE

myFile.close()

WRITING TO A FILE FULL PSEUDOCODE

myFile = openWrite("results.txt")

myFile.writeLine("A* in Computer Science")

myFile.writeLine("Well done!")

myFile.close()

ASSEMBLY LANGUAGE

ADDAdds the value at the given memory address to the value in the
accumulator

SUBSubtracts the value at the given memory address to the value in the
accumulator

LDALoads the value at the given memory address into the accumulator

STAStores the value in the accumulator at the given memory address

BRZBranches to a given address if the value in the accumulator is zero

(conditional branch)

BRPBranches to a given address if the value in the accumulator is

positive (conditional branch)

BRABranches to a given address if the value in the accumulator is

positive (unconditional branch)

DATCreates a flag with a label at which data is stored

HLTStops the program at that line preventing the rest of the code from
executing

INPAllows the user to input a value which will be held in the accumulator

PROGRAMMING METHODOLOGIES
Most software development life cycles have some stages in
common ,these phases are known as the SDLC

ANALYSIS: Stakeholders state what they require from the finished product
to clearly define and identify the problem and system requirements. They
are defined by analysing strengths and weaknesses with the current way
this problem is being solved, considering types of data involved.

DESIGN: The different aspects of the new system are designed e.g. inputs,
outputs ,security features, hardware set up, user interface. A test plan can
also be made at this stage

DEVELOPMENT: The design is used to split the project into individual ,self-
contained modules which are allocated to teams for programming .The
solution is coded

TESTING: The program is tested against the test plan formed in the design
stage eg alpha testing(in house within the development team) ,beta
testing (carried out by end users to get feedback), white box testing
(testing based on internal structure of program testing all possible
routes),black box testing (testing without awareness of internal structure
using inputs and outputs within the software)

IMPLEMENTATION: Once the testing stage has been used to make

appropriate changes to the software, it is installed onto the users’ systems
.

EVALUATION: After the implementation stage the effectiveness of the

software is evaluated against the system requirements that was defined
during analysis. Considering
robustness ,reliability ,portability ,maintainability.

MAINTENANCE: Any errors or improvements are flagged by end

users .Programmers will regularly send out software updates to fix any
bugs/security issues. There are CORRECTIVE,ADAPTIVE AND PERFECTIVE
maintenances done

The arrangement of the above phases and how programmers move from
one phase to another is known as the software development methodology.
There are five main methodologies to be aware of.

WATERFALL LIFECYCLE

-series of stages completed in sequence from start to finish

-each phase has a well-defined start and end point

Analysisdesigndevelopmenttestingimplementationevaluation
maintenance
-the analysis stage has a feasibility study that uses TELOS (technical-with
available tech ,economic-affordable ,legal ,operational-successful to make,
scheduling-possible in time frame)

-if a change needs to be made within a project all levels between the
current one and the one being fixed has to be revisited , this makes it
inflexible and unsuitable to projects with changing requirements.

-best suited for well understood and stable requirements

-users have little inputs as they are only involved at the beginning and
end (analysis and evaluation)

RAPID APPLICATION DEVELOPMENT

-producing successive prototypes of the software until a final version is

produced and approved

-after initially approving that the program is feasible in the analysis stage
prototypes are designed, coded, tested and evaluated with the end user.

-The user then decides if they are satisfied with the system or if they need
further improvements to start a new cycle (iteration)

-Best suited for projects with rapidly changing requirements, it

emphasizes speed over full planning and may use reusable components

SPIRAL MODEL

-a risk driven development methodology ,any project has its own set of
unique risks associated with it the spiral model focuses on managing risk
at every stage

-the spiral model is more of a guide for development teams, and it

combines ideas from the waterfall model and iterative development

-it is not a fixed process followed in a specific order it is dependant on the

project and its unique risks -the risks identified guide what methodology is
best suitable

1) determine objectives ,identify alternatives and assess risks e.g. cost,

not meeting needs, wrong technology, security or performance issues

2)evaluate alternatives and reduce risks eg planning ,prototypes, research

,adjusting plans

3)develop and test following chosen methodology

4)review and plan next iteration

-the spiral repeats with each loop getting closer to the final high quality
completed product
-At the start of each iteration we analyse risks before deciding upon the
methodology and path taken

-it is a process model generator where the decisions on the development

methodology are made based on the risks identified

AGILE METHODOLOGIES

-refers to a group of methodologies

-focuses on idea that requirements will shift and change during

development -this can only be dealt with by developing software in an
iterative way

-A product is built in a series of iterations known as sprints; these are

short time boxed periods when a team has focussed goals to complete a
set amount of work

-Each sprint should ideally be a bite sized piece of focussed work in a

specified time frame no more than one to four weeks

-Each sprint has planning, designing ,developing,

testing ,deploying ,evaluate, launch

EXTREME PROGRAMMING

Not so much a methodology as a frame work

-it aims to produce VERY high-quality code and promotes developers

quality of life by encouraging them to adopt common practices e.g.
simplicity, communication feedback, courage ,respect.

-it is considered an agile framework that encourages regular small

iterative software releases

-the concepts of collective ownership and every team member being of

equal value

-some specific practice examples :pair programming(two people

developing together one writes other reviews) ,collective code
ownership(any developer can modify any part at any time), continuous
integration(integrate code changes into the main project for automatic
implementation testing) , code standards ,refactoring (reorganising and
structuring) etc

MERITS,DRAWBACKS AND USES OF PROGRAMMING

METHODOLOGIES

MERITS DRAWBACKS USES

Waterfall -straight forward -lack of flexibility -static ,low risk
to manage due to cant go back and project which
 sequential process make changes after needs little
-clearly each stage user input
documented as -no changing -eg general
each stage has requirements purpose
defined outputs -late testing software
discovering errors -clear
too late unchanging
-no risk analysis can requirements
cause problems eg embedded
-limited user system
involvement(start
and end)

Agile -produces high -poor documentation -small to

quality code -requires consistent medium
-flexible to interaction between projects with
changing user and unclear initial
requirements programmer requirements
-regular user input

Extreme -produces high -paired programming Small to

programmi quality code causes high labour medium
ng -constant user costs projects with
involvement -team work is unclear initial
means high essential requirements
usability -end user may not requiring
be able to be excellent
present usability
Spiral -thorough risk -expensive to hire -large risk
analysis and risk assessors intensive
mitigation -lack of focus on projects with
-caters to code efficiency high budget
changing user -high costs due to
needs constant prototyping
-produces
prototypes
throughout
Rapid -caters to -poorer quality Small to
Application changing user documentation medium low
Developme requirements -fast pace may budget projects
nt -highly usable reduce code quality with short time
finished product frames
-focuses on core
features reducing
development time

AGILE VS RAD
-agile focuses on incrementally building the full software through small
sprints ,each sprint can work on chunks of the project/various features

-RAD focuses on building prototypes that are not fully functional versions
of the software with key elements until user satisfaction is reached

BOTH iterative development methodologies where a cycle or phase in

which a portion of the project is worked on :developed,tested and
reviewed.