Program Implementation ITnotes

8/13/2019 Program Implementation ITnotes

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Where are we?We looked at problem solving

Writing algorithms

Drawing flowchartsTrace table

Now

Use of a programming language to introduce theprocess of writing short programs.


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Ms. Douglas and Mr. L:ucas


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ProgrammingProgramming is the art of writing the solution to a

problem using a language that a computer canunderstand.

A programmer instructs the computer how to solve aproblem since it cannot come up with a solution all by

itself. (The person that write programs)


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Computer ProgramA computer program is a set of instructions that tells a

computer what to do and how to do it.

These instructions are converted into a sequence of

numeric codes called machine codewhich is storedin memory.

CPU interprets the code in order to carry out the

instructions of the program


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Types of Programming languageLow-level language

High-level language


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Low-level LanguageLanguage is machine dependent. Other words, codes

written can only be understood by the particularcomputer or processor used to write the code.

Types of low-level language:

First generation language

Second generation language


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First generationlanguage

Second generationlanguage

It is called machine language. It usedthe digits 0 and 1 to make up binarycode.

It is called assembly language. It hasthe same structure and commands asmachine language but instead ofusing binary to write codes it usedequivalent assembly language code.E.g. 10110000 01100001 : add A, B

Advantage:Code runs very fast and efficientlybecause it is directly executed by theCPU

Advantage:Can be easily converted to machinecode by a program called anassembler

Disadvantage:Programmer may become confused

with the massive amount of 0s and 1sin the program.It is machine dependent.

Disadvantage:Still difficult to understand comparedto the high-level language.It is machine dependent.


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High-Level LanguagesHigh level language are notmachine dependent.

Therefore programs written on one computer can beused on another similar computer.

Keywords used are similar to English and easier towrite

Types of high-level language

Third generation languages (3GLs)Fourth generation languages (4GLs)

Fifth generation language (5GLs)


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3GLs 4GLs 5GLsThese languages areconverted to machine

code. E.g. FORTRAN,BASIC, C

Non-procedural: programssuch as COBOL are written

to provide easy ways ofdesigning screens andreports and using databases.They contain commands toread and process the dataand place the results in

report-form on the page

Very high level languages.5GLs are non-procedural

languages meaning that theprogrammer states the goalto be achieved but not thesteps required in order toachieve the goal. E.g. Prolog

Advantage:Can use English-typewords to write programcode, making it easier tocreate.

Advantage:Useful for generating reports

Advantage:Computers will be able tocommunicate in naturalspoken language with theirusers

Disadvantage:Programsalso have to be convertedto machine language(binary).

Disadvantage:Can become very wordy.

Disadvantage:Very complex to design,programmer must be highlytrained.


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Third Generation Language FORTRAN (Formula Translation) - First high-level language, used to

express mathematical formulae, Scientific problem and engineerproblem.

BASIC (Beginners All-purpose Symbolic Instruction Code) - Very easyto learn language that was creating teach programming.

COBOL (Common Business Oriented Language) A language used incommercialsand business.

PASCAL ( named after the 17thcentury Mathematician Blaise Pascal) use for teachingand alternative to BASIC


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Third Generation Language C A language used mostly to write Operating

Systems,Database Management Software andScientificApplication.

C++ - An Object Oriented Programming Languagethat was originally an extension of C.

PROLOG (Programming Logic) A language used todevelop artificial intelligence.


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Review Questions1) Explain difference between low-level languages and

high level languages.

2) State the generations of computer languages.3) State the programming language that is associatedwith:

a. Artificial intelligence applications

b. Business applicationsc. Operating systems

d. Scientific Problems


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Answers1. Low-level languages are machine dependent and not

easy to understand by humans whereas, high levellanguages must be converted to machine languageand are easier to understand by humans

2. First, second, third, fourth, fifth

3. Prolog; COBOL; C or C++; Fortran


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The sequence of steps associated with

implementing a program Computer program is developed through the following

steps:1) Defining the problem

2) Analyzing the problem

3) Developing an algorithm or method

4) Write the computer program which implements thealgorithm

5) Testing and debugging the program6) Documenting the program

7) Maintain the program


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Defining the Problem Problem must be well defined so that there is no doubt

as to what is the solution

Must be clearly written so that it can be interpreted tohave only one meaning.

Eg. - calculate the sum of two numbers

- compute the average of a class- grade the scores of students in a class


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Analyzing the problem The process of finding out the operation is analyzing

Analyzing the problem involves:

Interpreting and understanding the problemDetermine:

input needs

processing required

output requiredcommands and programming

constructs required


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Developing AlgorithmAlgorithm: set of steps which when followed can lead

to the solution of a problem

Can be written using pseudo code

Pseudo code is a language consisting of English like

statement used to represent the steps in an algorithm.

Flow Chart: a pictorial representation of an algorithm.


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Programming Terms and Concept

Source Code: original text of a program written in highlevel language

The actual programming language statements is calledthe source code.

Object Code: output from a compiler or assembler.

The source code must be translated to machinelanguage.

Machine language is the object code


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Programming Terms and Concept

Compile or interpret: mean to change a program ortranslate a program from high level language to machinecode. (translators)

Two type of translator:

Interpreter- translates or converts programmingcodes line by line

Compliertranslates or converts all theprogramming codes at one time


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Programming Terms Dry Run: manually checking through the steps in a

program. Testing the program.

Debugging: correcting errors in the source codes of aprogram.

Logics: sequential order and comparison within the

program.

Logic Error: results that come from sequence instructions,faulty comparison and selection


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Programming Terms

Syntax is the very precise way in which the statement in aprogram must be written in order to be understand. Therefore , The language of the programming language is the syntax

of the language.

Syntax Error: results from not adhering to the rules of aprogramming language.

Run Time Error: errors occur while the program compilesor runs.


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Variable DeclarationVariable hold areas or spaces for data which a

program might use or manipulate.Variables are givennames, which can assign values such asnumber andtext. For example, age: integer.

Variable store values of a given type. Some data typeare:

Integer to store integer or whole number. Real to store real or functional numbers.

Character a single character such as a letter.

String collection of character such as a word.


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Variable DeclarationThis is how you declare variables in pseudo CodeInput Age, Cost, GradeAge= 23Cost 56.50Grade = A

This is how you declare variables in PascalVarAge :=integer;Cost := real;Grade:=char; Age

Assign Initial Values: Cost

Age:= 23; GradeCost:=56.50;Grade:=A;

56.50

A

23


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Variable Declaration

To declare a variable means to create the variable bygiving it a name and give it a data type (integer, realetc.

This is how you declare constants in pseudo Code

Input Price = 50, ItemName = cake

This is how you declare variables in Pascal and assigninginitial values:

Const

Price :=50;

Cost := Cake;


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control structures Conditional branching:

if-then if-then-else,

Program grade; Var grade :integer;

Begin Writeln(Enter your information technology grade); Read(grade); If (grade >= 50)

Then Writeln(Pass accepted for cxc)

Else Writeln( failed, try harder next time)

End


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control structures Loops: While

ProgramwhileLoop;

Var a:integer;

Begin a:= 40;

While a 0 DO a=a-5;

Writeln( The value of variable a is: , a);

End


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control structures Loops: Repeat

ProgramrepeatLoop;

Var a:integer;

Begin a:= 40;

Repeat a=a-5;


Until a=0;


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control structures Loops: For

ProgramforLoop;

Var a:integer;

Begin a:= 40;

For m=1 to 8 a=a-5;


End;


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Array Idimensional array

Is a set of data of the same type grouped together andreferred to by a single name.

23 33 56 41 79 38

Position1

Position2

Position3

P

osition4

Position5

Position6

AGE[6]

VARAGE: ARRAY[1..6] OF INTERGER;


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Reading from Array Reading from Array Program WriteArray;

Var i: integer; day: array[1..7] of real;

Begin Day[1]:= Sunday; Day[2]:= monday; Day[3]:= tuesday; Day[4]:= wednesday; Day[5]:= thursday; Day[6]:= friday; Day[7]:= saturday;

Begin

writeln(which day of theweek is you favorite day);

Read(i) skipLine(3);

writeln(Your favorite dayis, day[1]);

End;

This line reads data to variable

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Program Implementation ITnotes