C LANGUAGE-FLOWCHARTS,PSEUDOCODE,ALGORITHMS APPROCHES

Unit 1
 Flowchart: Elements, Identifying and understanding
input/ output, Branching and iteration in flowchart
 Algorithm design: Problem solving approach(top
down/bottom up approach)
 Pseudo Code : Representation of different construct,
writing pseudo-code from algorithm and flowchart

Programming:
A typical programming task can be divided into two phases:
a) Problem solving phase: produce an ordered sequence of steps that
describe solution of problem. This sequence of steps is called an algorithm.
b) Implementation phase: Implement the program in some programming
language.

• A computer performs many tasks exactly in the same manner as it is told to do.
• This places responsibility on the user to instruct the computer in a correct and precise
manner, so that the machine is able to perform the required job in a proper way.
• A wrong or ambiguous instruction may sometimes prove disastrous. In order to instruct a
computer correctly, the user must have clear understanding of the problem to be solved.
• A part from this he should be able to develop a method, in the form of series of
sequential steps, to solve it.
• Once the problem is well-defined and a method of solving it is developed, then
instructing he computer to solve the problem becomes relatively easier task.

Problem Solving
• A computer cannot solve a problem on its own. One has to provide step by step solutions of the
problem to the computer. In fact, the task of problem solving is not that of the computer.
• It is the programmer who has to write down the solution to the problem in terms of simple
operations which the computer can understand and execute.
• In order to solve a problem by the computer, one has to pass though certain stages or steps.
They are :
1. Understanding the problem
2. Analyzing the problem
3. Outline problem requirements
4. Developing the solution/algorithm
5. Coding and implementation

1. Understanding the problem: Here we try to understand the problem to be solved in totally. Before
with the next stage or step, we should be absolutely sure about the objectives of the given problem.
2. Analyzing the problem: After understanding thoroughly the problem to be solved, we look different
ways of solving the problem and evaluate each of these methods. The idea here is to search an
appropriate solution to the problem under consideration. The end result of this stage is a broad
overview of the sequence of operations that are to be carries out to solve the given problem.
3. Outline problem requirements: identify requirements of the problem in terms of number of
variables required, formula etc
4. Developing the solution/algorithm: Here the overview of the sequence of operations that was the
result of analysis stage is expanded to form a detailed step by step solution to the problem under
consideration.
5. Coding and implementation: The last stage of the problem solving is the conversion of the detailed
sequence of operations in to a language that the computer can understand. Here each step is
converted to its equivalent instruction or instructions in the computer language that has been chosen
for the implantation.

Analyze the problem
1) Thoroughly understand the problem
2) Understand problem requirements
 does the program require interaction?
 does program manipulate data?
what will be the output?
3) If the problem is complex, divide it into subproblems
analyse each sub problem as above

Algorithm
Definition: A set of sequential steps that define how a task is to be performed.
• Solves a well specified problem in a general way.
• Algorithm remains the same independent of:
Which kind of hardware it is running on
Which programming language it is written in
• It may be possible to solve to problem in more than one ways, resulting in more than one
algorithm.
• The choice of various algorithms depends on the factors like reliability, accuracy and easy to modify.
• The most important factor in the choice of algorithm is the time requirement to execute it, after
writing code in High-level language with the help of a computer.
• The algorithm which will need the least time when executed is considered the best.

Algorithm Properties/characteristics
1. Input/output: Each algorithm must take zero, one or more quantities as input data
produce one or more output values.
2. Finiteness: An algorithm must terminate in a finite number of steps
3. Definiteness: Each step of the algorithm must be precisely and unambiguously stated
4. Effectiveness: Each step must be effective, in the sense that it should be primitive easily
(convert able into program statement) can be performed exactly in a finite amount of time.
5. Generality: The algorithm must be complete in itself so that it can be used to solve
problems of a specific type for any input data.
An algorithm can be written in English like sentences or in any standard representation
sometimes, algorithm written in English like languages are called Pseudo Code

Steps involved in algorithm development
• An algorithm can be defined as “a complete, unambiguous, finite number of logical
steps for solving a specific problem “
• Step1. Identify input: For an algorithm, there are quantities to be supplied called
input and these are fed externally. The input is to be identified first for any specified
problem.
• Step2: Identify output: From an algorithm, at least one quantity is produced, called
for any specified problem.
• Step3 : Identify processing operations : All the calculations to be performed in order
to lead to output from the input are to be identified in an orderly manner.
• Step4: Processing Finiteness : If we go through the algorithm, then for all cases, the
algorithm should terminate after a finite number of steps.

Algorithm constructs
1) Sequence
a number of instructions are processed one after another.
statement 1;
statement 1;
statement 1;
2) Decision /selection
The next instruction to be executed depends on a 'condition’ :
if (condition is true) then
statement 1;
else
statement 2;
else
statement 3;
end if

3) Iteration
if want to perform a number of steps again and again
a) …. A fixed number of times
for 20 times do
statement 1;
statement 2;
……………
end do
b) ….. Until a condition is met

Example 1 : write algorithm to find the average of three numbers
• Step 1 start
• Step 2 Read the numbers a, b, c
• Step 3 Compute the sum of a, b and c
• Step 4 Divide the sum by 3
• Step 5 Store the result in variable d
• Step 6 Print the value of d
• Step 7 End

Example 2 : Write an algorithm to calculate the simple interest using the formula.
Simple interest = P*N* R/100.
Where P is principle Amount, N is the number of years and R is the rate of interest.
Step 1: start
Step 2 : Read the three input quantities’ P, N and R.
Step 3 : Calculate simple interest as Simple interest = P* N* R/100
Step 4: Print simple interest.
Step 5: Stop.

Example: Write an algorithm to calculate the perimeter and area of
rectangle. Given its length and width.
Step 1: start
Step 2: Read length of the rectangle.
Step 3: Read width of the rectangle.
Step 4: Calculate perimeter of the rectangle using the formula
perimeter = 2* (length + width)
Step 5: Calculate area of the rectangle using the formula
area = length *width.
Step 6: Print perimeter.
Step 7: Print area.
Step 8: Stop.

Questions : write algorithm and program
1) The distance between two cities(in km) is input through the keyboard. Write an algorithm and
program to convert and print this distance in meters, feet, inches and centimeters
2) Two numbers are input through the keyboard into locations C and D. write an algorithm and
program to interchange the contents of C and D
3) Write an algorithm to find whether the number is even or odd.
4) Write an algorithm to print whether the
5) Write an algorithm to print sum, mult, sub, div of two numbers
6) Write an algorithm to calculate simple interest.
7) Write an algorithm to read 3 numbers from the user. Print their sum and average.
8) Write an algorithm to read basic salary from the user and compute HRA – 12% of basic, DA- 64%
of basic, allowance -15% of basic. Also display total salary.
9) Write an algorithm to find area and perimeter of square
10) Write an algorithm to find area and perimeter of circle
11) Write an algorithm to find area of triangle using hero’s formula

Algorithm design:
Problem solving approach
(top down/bottom up approach)

• A programming approach is nothing but way of solving the computational
problem.
• Two approaches:
a) Top down
b) Bottom up

Top down approach
• “top down” approach is nothing but resolving the problem from high level to low level.
Basically you start from the whole problem.
• Top down :
1) Take the whole problem and split it into two or more parts.
2) Find solution to these parts.
3) If these parts turn out to be too big to be solved as a whole, split them further and find
find solutions to those sub-parts.
4) Merge solutions according to the sub-problem hierarchy thus created after all parts have
been successfully solved.

Bottom up approach
• In "bottom up" approach, you identify lower-level tools that you can compose to become a
bigger program. Basically you focus on parts of the problem to solve it.
• Bottom up :
1) Breaking the problem into smallest possible(and practical) parts.
2) Finding solutions to these small sub-problems.
3) Merging the solutions you get iteratively(again and again) till you have merged all of them
to get the final solution to the "big"
problem.
The main difference in approach is splitting versus merging. You either start big and split
"down" as required or start with the smallest and merge your way "up" to the final solution.

Program structure in top down Vs bottom up approach

C LANGUAGE-FLOWCHARTS,PSEUDOCODE,ALGORITHMS APPROCHES

Role of sub algorithm
• Algorithms are often broken down into smaller chunks, called Subalgorithm. This is both so that they are easier to
read, and also because then parts of the algorithm can be reused.
• A sub-algorithm is an algorithmic module which is complete in itself and has independent existence.
• It can be used or called by some main algorithm or by some other sub-algorithm.
• It may or may not receive values from a calling algorithm. These values are called arguments or
parameters.
• The sub-algorithm performs its task and then sends back the result to the calling algorithm. It can be
called by many different algorithms or called at different places in the same algorithm.
• The relationship between an algorithm and a sub-algorithm is similar to the relationship between a
main program (function) and a sub-program (sub-function) in a programming language.

Usefulness
• When the problem is very complex, it is divided into several independent
sub-problems. Each sub-problem is called sub-algorithm and can be
developed independently. These sub-problems can be combined together to
form the solution for the entire problem. Thus by using sub-algorithms the
complex problems can be solved easily.

Questions
1) C follows top down or bottom up approach? Why?
2) Give names of programming language which follows top down and
bottom up approach.
3) What is the role of subalgorithm? What is relationship between main
algorithm and sub algorithm?

Assignment: write algorithm
1) The current year and the year in which the employee joined the organization are entered through the keyboard.
If the number of years for which the employee has served the organization is greater than 3 then a bonus of
Rs. 2500/- is given to the employee. If the years of service are not greater than 3, then the program should do
nothing.
2) In a company an employee is paid as under:
If his basic salary is less than Rs. 1500, then HRA = 10% of basic salary and DA = 90% of basic salary. If his
salary is either equal to or above Rs. 1500, then HRA = Rs. 500 and DA = 98% of basic salary. If the employee's
salary is input through the keyboard write a program to find his gross salary.
3) The marks obtained by a student in 5 different subjects are input through the keyboard. The student gets a
division as per the following rules:
Percentage above or equal to 60 - First division
Percentage between 50 and 59 - Second division
Percentage between 40 and 49 - Third division Percentage less than 40 - Fail
calculate the division obtained by the student.

4) Calculate salary
5) If the ages of Ram, Shyam and Ajay are input through the keyboard. determine the youngest of the three.
6) Two numbers are input through the keyboard into locations C and D. write an algorithm and program to interchange the
contents of C and D
7)Write an algorithm to find whether the number is even or odd.
8) Write algorithm to check whether a triangle is valid or not, when the three angles of the triangle are entered through
the keyboard. A triangle is valid if the sum of all the three angles is equal to 180 degrees.

7) A company insures its drivers in the following cases: −
- If the driver is married.
- If the driver is unmarried, male & above 30 years of age.
- If the driver is unmarried, female & above 25 years of age.
8) Any integer is input through the keyboard. find out whether it is an odd
number or even number.
9) Any year is input through the keyboard. Determine whether the year is a
leap year or not. (Hint: Use the % (modulus) operator)

Unit 1
 Flowchart: Elements, Identifying and understanding
input/ output, Branching and iteration in flowchart
 Algorithm design: Problem solving approach(top
down/bottom up approach)
 Pseudo Code : Representation of different
construct, writing pseudo-code from algorithm and
flowchart

Like flowcharting, there are many elements to pseudocode design, only the
most
rudimentary are described here.
Get used to get information from the user
Display used to display information for the user
Compute perform an arithmetic operation
+
-
* Standard arithmetic operators
/
=
( )
Store Store a piece of information for later use

C LANGUAGE-FLOWCHARTS,PSEUDOCODE,ALGORITHMS APPROCHES

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