Notation

Notation

AU : Jan.-18, May-19, Dec.-19, Marks 8

The algorithmic specification is given by,

1. Pseudo Code

2. Flow Chart

3. Programming Languages Let us discuss them in detail

1. Pseudocode

Pseudocode is an artificial and informal language that helps programmers develop algorithms. Pseudocode is a "text-based" detail (algorithmic) design tool.

• The rules of Pseudocode are reasonably straightforward. All statements showing "dependency" are to be indented. These include while, do, for, if, switch.

For example

Example (1)

If student's age > 18

Print "Adult"

else

Print "Not an Adult"

Example (2)

Set sum:=0 Set

counter:= 1

While counter < = 10

Input the num sum:= sum+num

increment counter by 1 print the sum of 10 numbers

2. Flow Chart

• Flowcharts are the graphical representation of the algorithms.

• The algorithms and flowcharts are the final steps in organizing the solutions.

• Using the algorithms and flowcharts the programmers can find out the bugs in the programming logic and then can go for coding.

• Flowcharts can show errors in the logic and set of data can be easily tested using flowcharts.

Symbols used in Flowchart

Flow lines are used to indicate the flow of data. The arrow heads are important for flowlines. The flowlines are also used to connect the different blocks in the flowchart.

These are termination symbols. The start of the flowchart is represented by the name of the module in the ellipse and the end of the flowchart is represented by the keywords End or Stop or Exit

The rectangle indicates the processing. It includes calculations, opening and closing files and so on.

The parallelogram indicates input and output.

The diamond indicates the decision. It has one entrance and two exits. One exit indicates the true and other indicates the false,

The process module has only one entrance and one exit.

This polygon indicates the loop A indicates the starting of the counter S indicates the step by which the counter is incremented or decremented B indicates the ending value of the counter Using the counter the number of times the looping instruction gets executed.

The on-page connector connects the two different sections on the same page. A letter is written inside the circle. The off-page connector connects the two different sections on the different pages. The page numbers are used in off-page connector. These two symbols should be used as little as possible because then the readability of the flowchart may get affected.

 

Example 1.5.1 Draw the flowchart for sum of elements in an array.

Solution :

Fig. 1.5.1 Flowchart for sum of elements in array

 

Example 1.5.2 Convert the algorithm for computing factorial of given number.

Solution :

The algorithm for computing factorial of given number is

Read N

Set i and F to 1

While i < = N

F = F*i

Increase the value of i by 1

Display F

End

Fig. 1.5.2 Flowchart for factorial

 

Example 1.5.3 Draw a flow chart to accept three distinct numbers, find the greatest and print the result.

AU : Jan.-18, Marks 8

Solution :

Fig. 1.5.3

 

Example 1.5.4 Draw flow chart to find the sum of series 1 + 2 + 3 + 4 + 5 ...... + 100.

AU : Jan.-18, Marks 8

Solution : See Fig. 1.5.4 on next page.

3. Programming Languages

Definition : Programming languages are formal languages that have been designed to express computations.

There are various programming paradigm,

1. Imperative or procedural programming

2. Object oriented programming

3. Functional programming

4. Logic programming.

Fig. 1.5.4

Examples of various programming languages based on the above mentioned paradigm is as shown by following table

1. Imperative Programming Languages

• The imperative programming is also called as procedural programming language.

• A program consists of sequence of statements. After execution of each statement the values are stored in the memory.

• The central features of this language are variables, assignment statements, and iterations.

• Examples of imperative programming are - C, Pascal, Ada, Fortran and so on.

2. Object Oriented Programming Languages

• In this language everything is modeled as object. Hence is the name.

• This language has a modular programming approach in which data and functions are bound in one entity called class.

• This programming paradigm has gained a great popularity in recent years because of its characteristic features such as data abstraction, encapsulation, inheritance, polymorphism and so on.

• Examples of object oriented programming languages are - Smalltalk, C++, Java,

3. Functional Programming

• Computations of functional languages are performed largely through applying functions to values, i.e., (+ 10 20). This expression is interpreted as 10 + 20. The result 30 will be returned.

• For building more complex functions the previously developed functions are used. Thus program development proceeds by developing simple function development to complex function development.

• Examples of function programming are LISP, Haskell, ML

4. Logic Programming

• In this paradigm we express computation in terms of mathematical logic only. It is also called as rule based programming approach.

• Rules are specified in no special order.

• The logic paradigm focuses on predicate logic, in which the basic concept is a relation.

• Example of Logic programming is Prolog.

Review Questions

1. List the symbols used in drawing the flowchart.

AU : May-19, Marks 2

2. What is the use of algorithm, flowchart and pseudo code in the perspective of problem solving ?

AU : Dec.-19, Marks 2