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