Introduction to Programming
Algorithm Development with Flowchart
Steps in Problem Solving Process
(From our previous class)
 Understanding and analysis of the problem
 Development of algorithm i.e. devising a plan
 Coding and implementation
 Deployment and Maintenance
Note: At each stage there should be testing and proper
documentation.
ALGORITHM DEVELOPMENT PHASE
 Simply put, an algorithm is a set of instructions that describe
a method or a plan for solving a problem.
 An algorithm is a set of instructions for solving a problem or
sub problem in a finite amount of time using a finite amount
of data.
 These set of instructions must be unambiguous. This means
we aim to make what is ambiguous i.e. implicit in human
solution unambiguous i.e. explicit.
 Example of an ambiguous statement is: “stay away from the
bank”, the bank have different meanings e.g. bank of river, or
bank where money is kept, thus the statement “stay away
from bank” is ambiguous and such instruction should be
made explicit enough so that the computer can execute it.
Algorithm
Algorithm:
 a precisely specified procedure for
solving a problem or
a step-by-step method to solve a
problem or complete a task
Important Properties of Algorithms
 A good algorithm must be:
 Correct
 always returns the desired output for all legal instances of the
problem.
 Unambiguous
 Precise
 Efficient
 Can be measured in terms of
 Time
 Space
 Time tends to be more important i.e. tradeoff
Algorithm contd
 A good algorithm should have the following attributes:
 Definiteness; it should be well defined, that is every
steps should be definite
 Finiteness; it should terminate after finite number of
times
 Input; it may or may not have inputs
 Output; it must produce some result
 Efficiency ; an efficient algorithm should execute
faster, and take less memory space
CORRECTNESS OF ALGORITHM (start 02/06)
Goal of solving a mathematical problem is to produce
an answer to a problem, thus if the answer is correct
then the process or steps are correct. On the contrary
the goal of a computer problem solving is process
correctness.
This means if a process produces a correct result on a
certain data set, other data set will be used on the
same process in order to validate and test that the
process is correct.
Algorithm
 In writing algorithm we make use of symbols and action
keywords.
Algorithmic Symbols
 Symbol used in algorithm
=
Equal to
#
Not equal to
>
Greater than
<
Less than
 >=
greater than or equal to
 <=
Less than or equal to
 ↑ or ^ exponentiation
Algorithmic Action words
 Common Action Keywords
 Several keywords are often used to indicate
common input, output, and processing
operations in algorithm
 Input: READ,OBTAIN, GET, INPUT
 Output: PRINT, DISPLAY, SHOW, PUT
 Compute: COMPUTE, CALCULATE,
DETERMINE
 Initialise: SET, INIT
Examples of Algorithms
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Algorithm 1: Add two numbers entered by the user
Step 1: Start
Step 2: Declare variables num1, num2 and sum.
Step 3: Read values num1 and num2.
Step 4: Add num1 and num2 and assign the result to sum.
sum←num1+num2
 Step 5: Display sum
 Step 6: Stop
Examples of Algorithms
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Algorithm 2: Area of a rectangle
Step 1: Start
Step 2: Declare variables length, breadth and area.
Step 3: Read values length and breadth.
Step 4: Multiply length and breadth and assign the result to area.
area← length*breadth
 Step 5: Display area
 Step 6: Stop
Examples of Algorithms
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Algorithm 3: Find the largest number among two numbers
Step 1: Start
Step 2: Declare variables a and b.
Step 3: Read variables a and b.
Step 4: If a > b
Display a is the largest number.
Else
Display b is the largest number.
 Step 5: Stop
Lab I
 Write an algorithm to calculate the average of 3 integer numbers
 Write an algorithm to calculate simple interest using the expression
SI= (SRT/100)
Discussion
 Why do we study or write algorithm?
Algorithm Contd.
 Aim of programming methodology is:
 To develop a good algorithm programming methodology must be
followed.
Programming Methodology
 Programming methodology is an organized, documented set of procedures and guidelines for
one or more phases of the software life cycle. such as analysis or design.
 Programming methodology is about good software engineering principles.
 This are the principles to understand in order to develop a good software system.
 Thus we have programming methodology which deals with how an algorithm is developed.
 In this course we want to learn programming language in line with program methodologies
that make you a good programmer.
Types of Programming Methodology
 We have two types of programming methodologies,
they are:
1. Top down design
2. Object oriented design (OOD)
 Top-down approach uses divide and conquer technique where the
problem is broken down into sub problems, such that each sub
problems or modules can be solved (i.e. conquered) independently of
the other. This methodology is used by procedural languages like C.
Each sub-problem forms a procedure.
 An object oriented design is used majorly by object oriented
programming languages like Java, and C++. This breaks problems
down into objects.
PROGRAMMING METHODOLOGY
 Each of these methodologies can be expressed in any of these
forms:
 Diagramming notation for documenting the results of the
procedure (flowchart, UML design etc);
 step-by-step “cookbook” approach for carrying out the
procedure (pseudo code);
 and an objective set of criteria for determining whether the
results of the procedure are of acceptable quality e.g.
computational cost, time and space complexity etc.
Developing an algorithm
 As said earlier an
algorithm
can
be
represented as either a
flowchart or a pseudo
code.
Flowchart
Flowchart
A flow chart is a pictorial
representation of an algorithm in
which symbols are used to show the
various operations and decisions to be
followed in solving a problem.
In summary steps that must be
followed.
Flowchart Symbols
Flowchart symbol
Explanation
Terminal symbol; indicate start/stop/End
Parallelogram indicate input to and output
From computer memory. An input/output block has one entrance and only one
exit
Rectangle indicate Processing and data manipulation: define the calculation
require (e.g. computation of tax, gross pay, etc in above example)
The diamond indicates a decision. It has one entrance and two and only two exits.
One exit is the action when the resultants is True and the other exit is the action
when the resultant is False
Connector : this is used for the purpose of junction. Some rimes the flow chart
can’t be completed on a single page and it require 2 or more pages, these
connector symbols is used.
flow lines ; used to connect the various
symbols. It define the logic of the
algorithm
Rectangle with lines down each side indicates the process of modules. They have
one entrance and only one exit.
This is called predefined process..
Flowchart
Start
 This flowchart shows the
steps that may be taken in
solving the lamp problem.
End
Flowchart Steps
 Start from the first stage of problem solving process
 Draw the start symbol
 Draw the input symbol and indicates if the inputs (this step is optional)--- input is based on the identified input in problem solving process
 Based on processing requirement you may need the following symbols:
 Processing symbol for computation
 Decision symbol for making decisions
 Remember to use the arrows to show direction of flow of the steps
 The output will be the expected result
 Indicate the end symbol and use the necessary arrows to show how
each symbol moves to the end.
Group Work
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Design a flowchart for the followings:
admission process
hall registration process
student registration process
daily activities of Babcock student
Lab II
 Draw the flowchart for examples 1 and 2.
 The volume of a cylinder is given by
 V = π r2h
 Write the algorithm and draw the flowchart
 The area of a circle is given by the formula
Area = πr2
write the algorithm and draw the flowchart.
Lab II Assignment
 Following the problem solving process find the sum,
product, difference, and quotient of any two numbers.
 Design the flowchart
Self Assessment
 Why do we study programming methodology?
 What is the relationship between programming methodology and
algorithm development?
Assignment
 Draw a flowchart to authenticate student before having access to
Babcock webpage.
 Draw a flowchart to add any two numbers
 Draw a flowchart to add any two numbers while each number must not
be greater than 10.
 Draw a flowchart to detect whether a number is even or odd.
QUIZ 18/9
 What is an algorithm?
 Specify the type of data to use the followings algorithm keywords for
 INPUT
 INIT
 SET
PSUEDOCODE
 pseudocode is the way of expressing a program or code so that it could
be easily understood by programmers of every programming languages
out there.
 Pseudocode is an informal high-level description of the operating principle
of a computer program or an algorithm
Following are the basic rules before writing pseudocode :
 Write only one statement per line.
 Write what you mean, not how to program it
 Give proper indentation to show hierarchy and make code
understandable.
 Make the program as simple as possible.
 Conditions and loops must be specified well ie. begun and
ended explicity
 WRITE A PSEUDOCODE TO FIND THE SUM OF TWO NUMBERS.
begin
numeric nNum1,nNum2,nSum
display "ENTER THE FIRST NUMBER : "
accept nNum1
display "ENTER THE SECOND NUMBER : "
accept nNum2
compute nSum=nNum1+nNum2
display "SUM OF THESE NUMBER : " nSum
end
BEGIN
NUMBER s1, s2, sum
OUTPUT("Input number1:")
INPUT s1
OUTPUT("Input number2:")
INPUT s2
sum=s1+s2
OUTPUT sum
END
 WRITE A PSEUDOCODE TO FIND THE AREA OF RECTANGLE.
begin
numeric nLen,nBrd,nAre
display "ENTER THE LENGTH OF RECTANGLE : "
accept nLen
display "ENTER THE BREADTH OF RECTANGLE : "
accept nBrd
nAre=nLen*nBrd
display "AREA OF RECTANGLE : " nAre
end
BEGIN
NUMBER len,brt,area,perimeter
INPUT len
INPUT brt
area=len*brt
perimeter=2*(len+brt)
OUTPUT area
OUTPUT perimeter
END
 WRITE A PSEUDOCODE TO FIND THE GREATEST OF TWO NUMBERS.
begin
numeric nNum1, nNum2
display "ENTER THE FIRST NUMBER : "
accept nNum1
display "ENTER THE SECOND NUMBER : "
accept nNum2
if(nNum1>nNum2)
begin
display "GREATEST ONE : " nNum1
end
else
begin
display "GREATEST ONE : " nNum2
end
end
 WRITE A PSEUDOCODE TO FIND THE GREATEST OF THREE NUMBERS.
BEGIN
NUMBER num1,num2,num3
INPUT num1
INPUT num2
INPUT num3
IF num1>num2 AND num1>num3 THEN
OUTPUT num1+ "is higher"
ELSE IF num2 > num3 THEN
OUTPUT num2 + "is higher"
ELSE
OUTPUT num3+ "is higher"
ENDIF
END
 WRITE A PSEUDOCODE TO CHECK WHETHER THE ENTERED NUMBER IS
EVEN OR ODD.
begin
numeric nNum
display "ENTER A NUMBER : "
accept nNum
if(nNum%2==0)
begin
display "EVEN"
end
else
begin
display "ODD"
end
end
 WRITE A PSEUDOCODE TO CHECK EQUIVALENCE OF TWO NUMBERS.
USE IF STATEMENT.
begin
numeric nNum1, nNum2
display "ENTER THE FIRST NUMBER : "
accept nNum1
display "ENTER THE SECOND NUMBER : "
accept nNum2
if(nNum1==nNum2)
begin
display "THESE ARE EQUAL"
end
else
begin
display "THESE ARE NOT EQUAL"
end
end