Lesson 1 of c programming algorithms and flowcharts.pptx

Programming For Problem
Solving (PFPS)
LECTURE 1
Introduction to Algorithms and
Flowcharts

Algorithms and Flowcharts
• Algorithm and flowchart are the powerful tools
for learning programming
• An algorithm is a step-by-step analysis of the
process, while a flowchart explains the steps of a
program in a graphical way.
• Algorithm and flowcharts helps to clarify all the
steps for solving the problem.
• For beginners, it is always recommended to
first write algorithm and draw flowchart for
solving a problem and then only write the
program.
2

Algorithms
• A typical programming task can be divided into two
phases:
• Problem solving phase
– Produce an ordered sequence of steps that describe
solution of problem
– This sequence of steps is called an algorithm
– An algorithm is a sequence of steps to solve a particular
problem
– An algorithm is defined as an ordered set of unambiguous
steps that produces a result and terminates in a finite time
• Implementation phase
– Implement the program in some programming language
3

Steps In Problem Solving
• First produce a general algorithm called
pseudocode.
• Pseudocode is an artificial and informal
language that is very similar to everyday
English. It helps programmers develop
algorithms.
• Refine the algorithm successively to get step
by step detailed algorithm that is very close to
a computer language.
4

Characteristics of an Algorithm
• Algorithm has the following characteristics
– Input: An algorithm may or may not require input
– Output: Each algorithm is expected to produce at
least one result
– Definiteness: Each instruction must be clear and
unambiguous.
– Finiteness: If the instructions of an algorithm are
executed, the algorithm should terminate after
finite number of steps
5

Control Structures Involved In
Algorithm and Flowchart
• The algorithm and flowchart include following three
types of control structures.
– Sequence: In the sequence structure, statements are
placed one after the other and the execution takes place
starting from up to down.
– Branching (Conditional): In branch control, there is a
condition and according to a condition, a decision of
either TRUE or FALSE is achieved. In the case of TRUE, one
of the two branches is explored; but in the case of
FALSE condition, the other alternative is taken. Generally,
the ‘IF-THEN’ construct is used to represent branch
control.
– Loop (Repetition): The Loop or Repetition allows a
statement(s) to be executed repeatedly based on certain
loop condition using WHILE, Do-WHILE and FOR loops.
6

Example of Pseudocode and Algorithm
• Example 1: Write the pseudocode and detailed algorithm
to determine a student’s final grade and indicate whether
the student is passing or failing. The final grade is
calculated as the average of four marks.
• Pseudocode:
– Input a set of 4 marks
– Calculate their average by adding the marks and
dividing the sum by 4
– if average is below 50
Print “FAIL”
else
Print “PASS
7

Example of Pseudocode and Algorithm
• Detailed Algorithm
– Step 1: Input M1,M2,M3,M4
– Step 2: GRADE = (M1+M2+M3+M4)/4
– Step 3: if (GRADE < 50) then
Print “FAIL”
else
Print “PASS”
endif
8

Advantages of Algorithm
• It is a step-wise representation of a solution to a
given problem, which makes it easy to
understand.
• An algorithm uses a definite procedure.
• It is not dependent on any programming
language, so it is easy to understand for anyone
even without programming knowledge.
• Every step in an algorithm has its own logical
sequence so it is easy to debug.
9

Flowchart
• Flowchart is defined as a diagrammatic /graphical
representation of sequence of steps to solve a
problem.
• By looking at a flowchart, any one can easily
understand the operations and sequence of steps
involved in the solution
• Flowchart is often considered as a blueprint of a
design used for solving a specific problem
• Different symbols are used to draw each type of
flowchart.
10

Advantages of Flowchart
• Flowchart is an excellent way of communicating the logic of a
program.
• It provides an easy and efficient way to analyze the solution to
a problem.
• During program development cycle, the flowchart plays the
role of a blueprint, which makes the program development
process easier.
• After successful development of a program, it needs
continuous timely maintenance during the course of its
operation. The flowchart makes program or system
maintenance easier.
• It is easy to convert the flowchart into any programming
language code.
11

12
Standard Symbols Used in a Flowchart

Control Structures Representation in
Flowchart
13

Symbols Used in Algorithm and
Flowchart
• Assignment Symbol (← or =) is used to assign
value to the variable. E.g., to assign value 5 to
the variable HEIGHT, statement is HEIGHT ← 5
or HEIGHT = 5
• The symbol ‘=’ is used in most of the
programming language as an assignment symbol,
the same has been used in all the algorithms and
flowcharts in the manual
• The statement C = A + B means that add the
value stored in variable A and variable B then
assign/store the value in variable C
14

17
GO TO statement is also called unconditional transfer of
control statement is used to transfer control of execution to
another step/statement. E.g. the statement GOTO n will
transfer control to step/statement n.
Note: We can use keyword INPUT or READ or GET to accept
input(s) /value(s) and keywords PRINT or WRITE or DISPLAY
to output the result(s).

Sequential: Algorithm and Flowchart
18

19
Branching (Selection): Algorithm and
Flowchart

Looping: Algorithm and Flowchart
20

Lesson 1 of c programming algorithms and flowcharts.pptx

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