Notation

NOTATIONS

FLOW CHART

Flow chart is defined as graphical representation of the logic for problem solving.

The purpose of flowchart is making the logic of the program clear in a visual representation.

Rules for drawing a flowchart

1.              The flowchart should be clear, neat and easy to follow.

2.              The flowchart must have a logical start and finish.

3.              Only one flow line should come out from a process symbol.

4. Only one flow line should enter a decision symbol. However, two or three flow lines may leave the decision symbol.

5. Only one flow line is used with a terminal symbol.

6. Within standard symbols, write briefly and precisely.

7. Intersection of flow lines should be avoided.

Advantages of flowchart:

1.              Communication: - Flowcharts are better way of communicating the logic of a system to all concerned.

2.              Effective analysis: - With the help of flowchart, problem can be analyzed in more effective way.

3.              Proper documentation: - Program flowcharts serve as a good program documentation, which is needed for various purposes.

4.              Efficient Coding: - The flowcharts act as a guide or blueprint during the systems analysis and program development phase.

5.              Proper Debugging: - The flowchart helps in debugging process.

6.              Efficient Program Maintenance: - The maintenance of operating program becomes easy with the help of flowchart. It helps the programmer to put efforts more efficiently on that part.

Disadvantages of flow chart:

1.              Complex logic: - Sometimes, the program logic is quite complicated. In that case, flowchart becomes complex and clumsy.

2.              Alterations and Modifications: - If alterations are required the flowchart may require re-drawing completely.

3.              Reproduction: - As the flowchart symbols cannot be typed, reproduction of flowchart becomes a problem.

4.              Cost: For large application the time and cost of flowchart drawing becomes costly.

PSEUDO CODE:

v   Pseudo code consists of short, readable and formally styled English languages used for explain an algorithm.

v   It does not include details like variable declaration, subroutines.

v   It is easier to understand for the programmer or non programmer to understand the general working of the program, because it is not based on any programming language.

v   It gives us the sketch of the program before actual coding.

v   It is not a machine readable

v   Pseudo code can’t be compiled and executed.

v   There is no standard syntax for pseudo code.

Guidelines for writing pseudo code:

v   Write one statement per line

v   Capitalize initial keyword

v   Indent to hierarchy

v   End multiline structure

v   Keep statements language independent

Common keywords used in pseudocode

The following gives common keywords used in pseudocodes.

1. //: This keyword used to represent a comment.

2. BEGIN,END: Begin is the first statement and end is the last statement.

3. INPUT, GET, READ: The keyword is used to inputting data.

4. COMPUTE, CALCULATE: used for calculation of the result of the given expression. 5. ADD, SUBTRACT, INITIALIZE used for addition, subtraction and initialization.

6. OUTPUT, PRINT, DISPLAY: It is used to display the output of the program.

7. IF, ELSE, ENDIF: used to make decision.

8. WHILE, ENDWHILE: used for iterative statements.

9. FOR, ENDFOR: Another iterative incremented/decremented tested automatically.

Syntax for if else:

IF (condition)THEN       

statement   

...                    

ELSE       

statement   

...                    

ENDIF    

Example: Greates of two numbers          

BEGIN

READ a,b

IF (a>b) THEN

DISPLAY a is greater

ELSE

DISPLAY b is greater

END IF

END

Syntax for For:

FOR( start-value to end-value) DO   

statement   

...                    

ENDFOR     

Example: Print n natural numbers

BEGIN

GET n

INITIALIZE i=1

FOR (i<=n) DO

PRINT i

i=i+1

ENDFOR

END

Syntax for While:

WHILE (condition) DO  

statement   

...                    

ENDWHILE           

Example: Print n natural numbers

BEGIN

GET n

INITIALIZE i=1

WHILE(i<=n) DO

PRINT i

i=i+1

ENDWHILE

END

Advantages:

v   Pseudo is independent of any language; it can be used by most programmers.

v   It is easy to translate pseudo code into a programming language.

v   It can be easily modified as compared to flowchart.

v   Converting a pseudo code to programming language is very easy as compared with converting a flowchart to programming language.

Disadvantages:

v   It does not provide visual representation of the program’s logic.

v   There are no accepted standards for writing pseudo codes.

v   It cannot be compiled nor executed.

v   For a beginner, It is more difficult to follow the logic or write pseudo code as compared to flowchart.

Example:

Addition of two numbers:

BEGIN

GET a,b

ADD c=a+b

PRINT c

END

PROGRAMMING LANGUAGE

A programming language is a set of symbols and rules for instructing a computer to perform specific tasks. The programmers have to follow all the specified rules before writing program using programming language. The user has to communicate with the computer using language which it can understand.

Types of programming language

1.              Machine language

2.              Assembly language

3.              High level language

Machine language:

The computer can understand only machine language which uses 0’s and 1’s. In machine language the different instructions are formed by taking different combinations of 0’s and 1’s.

Advantages:

Translation free:

Machine language is the only language which the computer understands. For executing any program written in any programming language, the conversion to machine language is necessary. The program written in machine language can be executed directly on computer. In this case any conversion process is not required.

High speed

The machine language program is translation free. Since the conversion time is saved, the execution of machine language program is extremely fast.

Disadvantage:

Ø   It is hard to find errors in a program written in the machine language.

Ø   Writhing program in machine language is a time consuming process.

Machine dependent: According to architecture used, the computer differs from each other. So machine language differs from computer to computer. So a program developed for a particular type of computer may not run on other type of computer.

Assembly language:

To overcome the issues in programming language and make the programming process easier, an assembly language is developed which is logically equivalent to machine language but it is easier for people to read, write and understand.

Ø   Assembly language is symbolic representation of machine language. Assembly languages are symbolic programming language that uses symbolic notation to represent machine language instructions. They are called low level language because they are so closely related to the machines.

Assembler

Assembler is the program which translates assembly language instruction in to a machine language.

Ø   Easy to understand and use.

Ø   It is easy to locate and correct errors.

Disadvantage

Machine dependent

The assembly language program which can be executed on the machine depends on the architecture of that computer.

Hard to learn

It is machine dependent, so the programmer should have the hardware knowledge to create applications using assembly language.

Less efficient

Ø   Execution time of assembly language program is more than machine language program.

Ø   Because assembler is needed to convert from assembly language to machine language.

High level language

High level language contains English words and symbols. The specified rules are to be followed while writing program in high level language. The interpreter or compilers are used for converting these programs in to machine readable form.

Translating high level language to machine language

The programs that translate high level language in to machine language are called interpreter or compiler.

Compiler:

A compiler is a program which translates the source code written in a high level language in to object code which is in machine language program. Compiler reads the whole program written in high level language and translates it to machine language. If any error is found it display error message on the screen.

Interpreter

Interpreter translates the high level language program in line by line manner. The interpreter translates a high level language statement in a source program to a machine code and executes it immediately before translating the next statement. When an error is found the execution of the program is halted and error message is displayed on the screen.

Advantages

Readability

High level language is closer to natural language so they are easier to learn and understand

Machine independent

High level language program have the advantage of being portable between machines.

Easy debugging

Easy to find and correct error in high level language

Disadvantages

Less efficient

The translation process increases the execution time of the program. Programs in high level language require more memory and take more execution time to execute.

They are divided into following categories:

1.              Interpreted programming languages

2.              Functional programming languages

3.              Compiled programming languages

4.              Procedural programming languages

5.              Scripting programming language

6.              Markup programming language

7.              Concurrent programming language

8.              Object oriented programming language

Interpreted programming languages:

An interpreted language is a programming language for which most of its implementation executes instructions directly, without previously compiling a program into machine language instructions. The interpreter executes the program directly translating each statement into a sequence of one or more subroutines already compiled into machine code.

Examples:

Pascal

Python

Functional programming language:

Functional programming language defines every computation as a mathematical evaluation. They focus on the programming languages are bound to mathematical calculations

Examples:

Clean

Haskell

Compiled Programming language:

A compiled programming is a programming language whose implementation are typically compilers and not interpreters.

It will produce a machine code from source code.

Examples:

C

C++

C#

JAVA

Procedural programming language:

Procedural (imperative) programming implies specifying the steps that the programs should take to reach to an intended state.

A procedure is a group of statements that can be referred through a procedure call. Procedures help in the reuse of code. Procedural programming makes the programs structured and easily traceable for program flow.

Examples:

Hyper talk

MATLAB

Scripting language:

Scripting language are programming languages that control an application. Scripts can execute independent of any other application. They are mostly embedded in the application that they control and are used to automate frequently executed tasks like communicating with external program.

Examples:

Apple script

VB script

Markup languages:

A markup language is an artificial language that uses annotations to text that define hoe the text is to be displayed.

Examples:

HTML

XML

Concurrent programming language:

Concurrent programming is a computer programming technique that provides for the execution of operation concurrently, either with in a single computer or across a number of systems.

Examples:

Joule

Limbo

Object oriented programming language:

Object oriented programming is a programming paradigm based on the concept of objects which may contain data in the form of procedures often known as methods.

Examples:

Lava

Moto