The document defines algorithms and different representations of algorithms such as normal English, flow charts, pseudo code, and programs. It provides examples of different control structures like sequence, selection, and repetition. Key points include: algorithms must be unambiguous, terminate in a finite number of steps, and time, memory, accuracy and generality are qualities of a good algorithm. Pseudo code uses keywords and indentation to represent program logic clearly. Flow charts use standard symbols and avoid intersecting lines to depict a process visually. Control structures determine the order of execution through sequencing, conditional checks, or repeated execution.

1. ALGORITHM

2. Definition:
• Algorithm is a finite sequence of
instructions required for producing the
desired result.
• It is also defined as “any problem whose
solution can be expressed in a list of
executable instruction.”

3. Characteristics:
• The steps in the algorithm must be
unambiguous .
• It should be written in sequence.
• Ensure that the algorithm will terminate.
• It should conclude after a finite number of
steps.

4. Quality of good algorithm:
• Time
• Memory
• Accuracy
• Sequence
• Generality

5. Representation of algorithm:
• Normal English -The algorithm is
represented in step by step sequential
order in normal English.
• Flow chart- It is a pictorial representation
of an algorithm.
• Pseudo code –it is a formal design tool
and utilized very well with the rules of
structure design and programming.

6. Contd..
• Decision table- it is used to helps a lot in
designing a specific segment of a design.
• Program - it is represented as a program
using any high level language.

7. Example
• Addition of two numbers
Step1: Start
Step2: Read a, b
Step3: Add the value of a with b and
store the result in c.
Step4: Display the value of c
Step5: Stop

8. PSEUDO CODE

9. Definition:
• Pseudo means imitates and code
means instruction.
• It is formal design tool.
• It is also called Program Design
Language.

10. Keywords
• READ,GET
• PRINT,DISPLAY
• COMPUTE,CALCULATE

11. Guidelines for writing Pseudo code
• Steps should be understandable
• Capitalize the keyword.
• Indent to show hierarchy.
• End multiple line structure etc,.

12. Example
READ a,b
C=a+b
WRITE C
stop

13. Example
READ a,b
IF a>b
PRINT a is greater
ELSE
PRINT b is greater
ENDIF
stop

14. Advantage & Disadvantage
• It can be easily modified
• It can be understood easily
• Compare to flowchart it is difficult to
understand the program logic.

15. Flowcharts
• It is the pictorial representation of the
algorithm.
• A flow chart, or flow diagram, is a
graphical representation of a process or
system that details the sequencing of
steps required to create output.
• A flowchart is a picture of the separate
steps of a process in sequential order.

16. Flowchart Symbols
• Terminal symbol
– It is used to represent the start, end of the
program logic.
• Input/Output
– It is used for input or output.
• Process Symbol
– It is used to represent the calculations,
data movements, initialization operations
etc,.

17. • Decision Symbol
– It is used to denote a decision to be made
at that point
• Flow lines
– It is used to connect the symbols
• Connectors
– It is used to connect the flow lines.

18. Rules for preparing
flowcharts
• It should be simple.
• Standard symbols should be used.
• The flow lines should not intersect each
others.
• In case of complex flowcharts use the
connectors symbols.

19. • Only one flow line should enter the
process symbol and only one flow line
should come out from a process symbol.
• Only one flow line used with the terminal
symbol.
START
STOP

20. • Only one flow line should enter the
decision symbol and two or three
flowlines may leave from the decision
symbol.

21. Benefits of Flowcharts
• Makes Logic Clear
• Communication
• Effective Analysis
• Useful in coding
• Useful in Testing etc,.

22. Limits of Flowcharts
• It is difficult to use flowcharts for large
program
• Difficult to modify
• Cost etc,.

23. Program control structures:
• Program control structure are defined as
the program statements that specifies the
order in which statements are executed.
• Types:
– Sequence control structure
– Selection control structure
– Repetition control structure

24. • The instructions are computed in
sequence i.e. it performs
instruction one after another.
• It uses top-down approach.
Sequence control
structure

25. Sequence control structure
Flow chart Pseudo code
Process 1
Process 2
Process nProcess 2
Process n
Process 1

26. Example
START
C=a+b
Print c
Read a,b
STOP

27. SELECTION CONTROL
STRUCTURE
• It is used for making decisions.
• It allows the program to make a choice
from alternative paths.
• IF …THEN
• IF …THEN… ELSE
• CASE etc.,

28. IF…THEN
Pseudo code Flow
chart
IF condition THEN
process 1
.
.
END IF
.
.
If
condition
NO
YES
Process 1

29. Example
Start
Read a
If a>0
Print a is Positive
Stop
no
yes

30. IF…THEN…ELSE
Pseudo code Flowchart
IF condition THEN
process 1
.
.
ELSE
process 2
.
.
END IF
.
.
If
condition
YES NO
Process 1 Process 2

31. Example
Start
Read a,b
If a>b
Print a is Greater
Print b is Greater
Stop
no
yes

32. CASE structure
Pseudo code Flow chart
.
.
CASE Type
Case Type-1:
Process 1
Case Type-2:
Process 2
.
.
Case Type-n:
Process n
.
.
END CASE
Type 1
Type 2
Type 3
Process 1
Process 2
Process 3
no
no
no
yes
yes
yes

33. start
stop
Read m1,m2,m3
Avg=(m1+m2+m3)/3
If
Avg>=60
If
Avg>=50
If
Avg>=35
Fail
Print
First Class
Print
Second Class
Print
Third Class
Example: Finding the Grade

34. Repetition control structure(looping)
• It is used to execute some instructions
several time based on some condition.
• WHILE loop
• Do…WHILE loop etc.,

35. WHILE Loop
Pseudo code Flow chart
WHILE condition
.
.
Body of the loop
.
.
END WHILE
Body of The loop
condition
no
yes

36. Example
Start
Num=0
Num=Num+1
Print Num
while
Num<5
stop
no
yes

37. DO…WHILE Loop
Pseudocode Flow chart
DO
.
.
Body of the loop
.
.
WHILE condition
.
.
END WHILE
Body of The loop
condition
no
yes

38. Example
Start
Num=0
Num=Num+1
Print Num
while
Num<5
stop
no
yes

39. Example: Finding the area of a
circle
Algorithm
Step1: Start
Step2: Read the value of r
Step3: Calculate area = 3.14*r*r
Step4: Print area
Step5: Stop