Fundamentals of C programming - Ompal Singh Sharda University,Gr.Noida

Fundamentals of C programming

- Ompal Singh

Sharda University,Gr.Noida

Topics

• Algorithm• Pseudo code• Flow Chart


Planning of Computer Programming- In today’s world a computer is used to solve various types of problems because it takes very less time as compared to a human being. 1. Analyze the given problem2. Divide the process used to solve the problem in a series of elementary task.3. Formulate the algorithm to solve the problem. Now in other words we say that “program must be planned before they are written”.

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

• Implementation phase – implement the program in some programming language


Algorithm• The Term Algorithm refers to the logic of a

program. It is a step-by-step description of a solution to the given problem.

• When sequence of instructions are executed in the specified format and sequence the desired result are obtained.

• Definition:- A format or set of steps for solving a particular problem is called as algorithm.

• It has clear starting and stopping point. With specific step by step instructions in each line.


Characteristics of Algorithm

• Each instruction should be precise and clear.• Each instruction should be executed in a finite

time.• One or more instructions should not be

repeated Infinitely.• After executing the instructions the desired

result are obtained.• It range from Simple to the Complex.


Process of algorithm

• An algorithm must express the steps in the solution in a way that will be suitable for computer processing.

• It Read Value perform a simple procedure and output the required result.

• After algorithm a Flowchart is prepared and than it is run in the language form in the computer.

Three constructs

Algorithm• Find area of a rectangle • Step 1: Input L,B

Step 2: area=L*BStep 3: Print area

Step 4: Exit• Find the area of a circle• Step 1: Input R

Step 2: area=3.14*R*RStep 3: Print area

Step 4: Exit


• Step 1: Input SP,CP Step 2: if (SP>CP) then

p=SP-CP Print p else

l=CP-SP Print l

endif Step 3:Exit


• 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

Step 4:Exit


Step 1: Input N1, N2, N3 Step 2: if (N1>N2) then if (N1>N3) then MAX ← N1 [N1>N2, N1>N3] else MAX ← N3 [N3>N1>N2] endif else if (N2>N3) then MAX ← N2 [N2>N1, N2>N3] else MAX ← N3 [N3>N2>N1] endif endif Step 3: Print “The largest number is”, MAX


• Detailed Algorithm • Step 1: Input M1,M2,M3,M4

Step 2: GRADE (M1+M2+M3+M4)/4 Step 3: if (GRADE > 60) then

Print “Ist” elseif (GRADE > 50)and (GRADE <60) then Print “IInd” else

Print “Fail”endif

Step 4:Exit


• Step 1: Input the value of NStep 2: Set i=1Step 3: Repeat step 4 and 5 until i<=N

Step 4: Print i Step 5: Set i=i+1 end loop Step 6: Exit


Pseudo code• First produce a general algorithm (one can use pseudo

code) • Refine the algorithm successively to get step by step

detailed algorithm that is very close to a computer language.

• Pseudo code is an artificial and informal language that helps programmers develop algorithms. Pseudo code is very similar to everyday English.


Pseudocode• Pseudocode is an informal description of analgorithm• English-like statements that require less precisionthan a formal programming language.• Allows the designer to focus on the logic of thealgorithm without being distracted by details oflanguage syntax.• A good pseudocode algorithm should beindependent of, but easily translated into, any formalprogramming language.


Pseudocode Control Structures• Sequence control structures Instructions are performed linearly• Conditional control structures A choice/selection is made between multiple courses of action• Looping/iteration control structures Enables repeating instructions within the algorithm A test condition determines when the repetition ends


Pseudocode Control Structures

• Selection and conditional1. if (condition) then2. statement 13. ...4. endif• • If the (condition) is TRUE then

statements between THEN and ENDIF are executed once


• Two-way decision1. if (condition) then2. statement 13. ...4. else5. statement n+16. ...7. endif

– • If the (condition) is TRUE then statements between THEN and ELSE are executed once

– • If the (condition) is FALSE then statements between ELSE and ENDIF are executed once


LOOP– For Loop– Used to implement statements that needs to be

repeated a fixed number of times.

1. for i ←1 to n2. Statement 13. ...4. next i• i is the index or counter that starts with some value and

increases by one every time through the loop until it reaches the given maximum value


Repeat …until

– Repeat Loop– Used to implement statements that needs to be repeated until the condition becomes TRUE.

1. repeat2. Statement 13. ...4. until (condition)


While LOOP

– While Loop– Used to implement statements that needs to be repeated while the condition is TRUE.

1. while (condition)2. Statement 13. ...4. endwhile


Advantages

• Converting a pseudo code to a programming language is easier than converting a flow chart to programming language.

• It is easier to modify the pseudo code of a program logic when program modification is necessary.

• Required less time and effort than flow chart.


Limitations

• A graphical representation of program logic is not available.

• There are no standard rules to follow in using pseudo code.

• It is very difficult for beginners.


Pseudocode

• Example 1: Write an algorithm to determine a student’s final grade and indicate whether it is passing or failing. The final grade is calculated as the average of four marks.


Pseudocode

Pseudocode:• Input a set of 4 marks• Calculate their average by summing and dividing by 4• if average is below 50

Print “FAIL”else

Print “PASS”



Flowchart• A Flowchart is a pictorial representation of an

algorithm.• The First flowchart is made by John Von

Newman in 1945.• It is a symbolic diagram of operation

sequence, dataflow, control flow and processing logic in information processing.

• The symbol used are simple and easy to learn.• It is a very help full tool for programmers and

beginners.

The Flowchart• (Dictionary) A schematic representation of a sequence of operations,

as in a manufacturing process or computer program.• (Technical) A graphical representation of the sequence of operations in

an information system or program. Information system flowcharts show how data flows from source documents through the computer to final distribution to users. Program flowcharts show the sequence of instructions in a single program or subroutine. Different symbols are used to draw each type of flowchart.


The Flowchart

A Flowchart– shows logic of an algorithm– emphasizes individual steps and their

interconnections– e.g. control flow from one action to the next



Purpose of flowchart

• Provide Communication.• Provide an overview.• Show all elements and its relationship.• Quick method of showing program flow.• Check program logic.• Facilitate coding.• Provide program revision.• Provide Program documentation.


Advantages of flowchart.

• Communication.• Effective analysis.• Proper documentation.• Efficient coding.• Proper debugging.• Efficient program maintenance.• Easy and clear presentation.


Limitation of flowchart

• Complex logic.• Drawing is time consuming.• Alteration and modification.• Redrawn many times.• Difficult to draw and remember.• Reproduction ( replica ).• Technical detail.


Symbols used in flowchart

• All symbols are of different shape and size.• All have specific meaning and use.• The ANSI ( American National Standard

Institute) group categories symbols in 3 types basic, specialized and additional symbols.

• These institution and standardized these basic symbols for use.


BASIC SYMBOLSTerminal Symbol = for start and stop.

INPUT and OUTPUT = Any function of input and output data.

Processing = An arithmetic and data movement instruction. Shows mathematical calculation and logic operations.


SYMBOLSDecision = Diamond indicate decision point in the program flow. IT may have 2 way branch or 3 way also.

Flow Lines = A Straight line between two boxes shows the path of logic flow in the program. An arrow head on the top of the line shows the direction of the flow, data from top to bottom and left to right.

Connectors = 2 small circles are used to connect separated portions of a flowchart without drawing lines between the parts. One connector indicated where the flow breaks off the other where it resumes.

Flowchart Symbols

Oval

Parallelogram

Rectangle

Diamond

Hybrid

Name Symbol Use in Flowchart

Denotes the beginning or end of the program

Denotes an input operation

Denotes an output operation

Denotes a decision (or branch) to be made. The program should continue along one of two routes. (e.g. IF/THEN/ELSE)

Denotes a process to be carried oute.g. addition, subtraction, division etc.

Flow line Denotes the direction of logic flow in the program


Basic

Flowcharts for three constructs

Example


PRINT“PASS”

Step 1: Input M1,M2,M3,M4Step 2: GRADE (M1+M2+M3+M4)/4 Step 3: if (GRADE <50) then

Print “FAIL” else

Print “PASS” endif

START

InputM1,M2,M3,M4

GRADE(M1+M2+M3+M4)/4

ISGRADE<50

PRINT“FAIL”

STOP

YN

Example 2

• Write an algorithm and draw a flowchart to convert the length in feet to centimeter.

Pseudocode:• Input the length in feet (Lft)• Calculate the length in cm (Lcm) by multiplying

LFT with 30• Print length in cm (LCM)


Example 2

Algorithm • Step 1: Input Lft• Step 2: Lcm Lft x 30 • Step 3: Print Lcm


START

InputLft

Lcm Lft x 30

PrintLcm

STOP

Flowchart

Example 3

Write an algorithm and draw a flowchart that will read the two sides of a rectangle and calculate its area.

Pseudocode • Input the width (W) and Length (L) of a rectangle• Calculate the area (A) by multiplying L with W• Print A


Example 3

Algorithm • Step 1: Input W,L• Step 2: A L x W • Step 3: Print A


START

InputW, L

A L x W

PrintA

STOP

Example 4

• Write an algorithm and draw a flowchart that will calculate the roots of a quadratic equation

• Hint: d = sqrt ( ), and the roots are: x1 = (–b + d)/2a and x2 = (–b – d)/2a

2 0ax bx c 2 4b ac


Example 4

Pseudocode: • Input the coefficients (a, b, c) of the quadratic

equation• Calculate d• Calculate x1• Calculate x2• Print x1 and x2


Example 4

• Algorithm: • Step 1: Input a, b, c• Step 2: d sqrt ( )• Step 3: x1 (–b + d) / (2 x a)• Step 4: x2 (–b – d) / (2 x a)• Step 5: Print x1, x2

4b b a c


START

Inputa, b, c

d sqrt(b x b – 4 x a x c)

Printx1 ,x2

STOP

x1 (–b + d) / (2 x a)

X2 (–b – d) / (2 x a)

Example 5

Thank you

Ompal Singh



Documents

Fundamentals of C programming - Ompal Singh Sharda University,Gr.Noida