Control structure of c

Control Structure in C
Made By: Komal Kotak
C.K.Pithawala College of Engineering and Technology

C Programming Definition
C is a high-level and general-
purpose programming language that is ideal for developing
firmware or portable applications. Originally intended for
writing system software, C was developed at Bell Labs by
Dennis Ritchie for the Unix Operating System (OS) in the
early 1970s

Conditions in C Programming
o C executes program sequentially.
o Sometimes a program requires checking of certain
conditions in program execution.
o C provides various key condition statements to check
conditions and execute statements according conditional
criteria.
o This statements are called decision making statements and
control statements.

Control Structure in C
Decision making structures require that the
programmer specifies one or more conditions to be
evaluated or tested by the program, along with a
statement or statements to be executed if the
condition is determined to be true, and optionally,
other statements to be executed if the condition is
determined to be false.
Show here is the general form of a typical decision
making structure found in most of the
programming languages −

if-else statement (1)
The if-else statement can exist in two
forms: with or without the else. The two
forms are:
if(expression)
statement
or
if(expression)
statement1
else
statement2
int a, b;
// ...
if(a < b) a = 0;
else b = 0;

Example: Odd Or Even No. Program
#include <stdio.h>
int main()
{
int number;
printf("Enter an integer: ");
scanf("%d",&number);
if( number%2 == 0 )
printf("%d is an even integer.",number);
else
printf("%d is an odd integer.",number);
return 0;
}
if-else statement (2)
Output
Enter an integer: 7
7 is an odd integer.

Nested if-else statement (1)
o The if...else statement
executes two different codes
depending upon whether the
test expression is true or false.
Sometimes, a choice has to be
made from more than 2
possibilities.
o The nested if-else statement
allows you to check for
multiple test expressions and
execute different codes for
more than two conditions.

Nested if-else statement (2)
Example: Program to relate two integers using =, > or <
#include <stdio.h>
int main()
{
int number1, number2;
printf("Enter two integers: ");
scanf("%d %d", &number1, &number2);
if(number1 == number2)
{
printf("Result: %d = %d",number1,number2); }
else if (number1 > number2)
{
printf("Result: %d > %d", number1, number2) }
else
{
printf("Result: %d < %d",number1, number2); }
return 0; }
Output
Enter two integers: 12
23
Result: 12 < 23

C Programming for Loop
Loops are used in programming to repeat a specific block until some
end condition is met.There are three loops in C programming:
1. for loop
2. while loop
3. do...while loop

For Loop (1)
o The initialization statement is executed only
once.
o Then, the test expression is evaluated. If the test
expression is false (0), for loop is terminated. But
if the test expression is true (nonzero), codes
inside the body of for loop is executed and the
update expression is updated.
o This process repeats until the test expression is
false.
o The for loop is commonly used when the number
of iterations is known.

For Loop (2)
Example: Program to calculate the sum of first n natural numbers
#include <stdio.h>
int main()
{
int num, i, sum = 0;
printf("Enter a positive integer: ");
scanf("%d", &num);
for(i = 1; i <= num; i++)
{
sum += i;
}
printf("Sum = %d", sum);
return 0;
}
Output
Enter a positive integer: 10
Sum = 55

while Loop (1)
o The while loop evaluates the test expression.
o If the test expression is true (nonzero), codes inside the body
of while loop is evaluated. The test expression is evaluated
again.The process goes on until the test expression is false.
o When the test expression is false, the while loop is
terminated.
o The syntax of a while loop is:
while (testExpression)
{
//codes
}
o where, testExpression checks the condition is true or false
before each loop.

while Loop (2)
Example: Program to find factorial of a number
#include <stdio.h>
int main()
{
int number;
int factorial;
printf("Enter an integer: ");
scanf("%d",&number);
factorial = 1;
while (number > 0)
{
factorial *= number;
--number;
}
printf("Factorial= %d", factorial);
return 0; }
Output
Enter an integer: 5
Factorial = 120

do-while Loop (1)
o The do..while loop is similar to the while loop with one important
difference.The body of do...while loop is executed once, before
checking the test expression. Hence, the do...while loop is executed at
least once.
o do...while loop Syntax
do
{
// codes
}
while (testExpression);
o The code block (loop body) inside the braces is executed once.
o Then, the test expression is evaluated. If the test expression is true,
the loop body is executed again.This process goes on until the test
expression is evaluated to 0 (false).
o When the test expression is false (nonzero), the do...while loop is
terminated.

do-while Loop (2)
Example: Program to add numbers until user enters zero
#include <stdio.h>
int main()
{
float number, sum = 0;
do
{
printf("Enter a number: ");
scanf("%f", &number);
sum += number;
}
while(number != 0.0);
printf("Sum = %f",sum);
return 0;
}
Output
Enter a number: 1.5
Enter a number: 2.4
Enter a number: -3.4
Enter a number: 4.2
Enter a number: 0
Sum = 4.70

break Statement (1)
o It is sometimes desirable to skip some statements inside the loop or terminate
the loop immediately without checking the test expression.
o In such cases, break and continue statements are used.
o The break statement terminates the loop (for, while and do...while loop)
immediately when it is encountered.The break statement is used with decision
making statement such as if...else.
o Syntax of break statement
break;

continue Statement
o The continue statement skips
some statements inside the loop.
The continue statement is used
with decision making statement
such as if...else.
o Syntax of continue Statement
continue;

Switch case Statement (1)
o The switch case statement evaluates the value of an
expression and a block of code is selected on the basis
of that evaluated expression.
o Each case refers back to the original expression.
o The data type that can be used in switch expression is
integer type only.
o Each case has a break statement.
o The switch case takes decision on the basis of
equality.

int main() {
char op;
int num1,num2;
printf("Enter an operator (+,-,*,/):");
scanf("%c", &op);
printf("Enter two operands: ");
scanf("%d %d",&num1, &num2);
switch(op)
{
case '+':
printf("%d + %d =
%d",num1, num2, num1+num2);
break;
case '-':
printf("%d - %d = %d",num1,
num2, num1-num2);
break;
case '*':
printf("%d * %d = %d",num1,
num2, num1*num2);
break;
case '/':
printf("%d / %d = %d",num1,
num2, num1/num2);
break;
default:
printf("Error! op is not
correct");
}
return 0;
}

Output
Enter an operator (+, -, *,): -
Enter two operands: 32
12
32 - 12 = 20

goto Statement (1)
o The goto statement is used to alter the normal sequence of a C program.
o Syntax of goto statement
goto label;
... .. ...
... .. ...
... .. ...
label:
statement;
o The label is an identifier. When goto statement is encountered, control of the
program jumps to label: and starts executing the code.

goto Statement (2)
Example: To check whether you can
vote or not
int main()
{
int age;
Vote:
printf("you are eligible for
voting");
NoVote:
printf("you are not eligible to
vote");
printf("Enter your age:");
scanf("%d", &age);
if(age>=18)
goto Vote;
else
goto NoVote;
return 0;
}
Output
Enter your age:15
You are not eligible to vote

Reason to avoid goto Statement
o The use of goto statement may lead to code that is buggy and hard to follow. For example:
one:
for (i = 0; i < number; ++i)
{
test += i;
goto two;
}
two:
if (test > 5) {
goto three;
}
... .. ...
Also, goto statement allows you to do bad stuff such as jump out of scope.
o That being said, goto statement can be useful sometimes. For example: to break from nested loops.

Control structure of c

More Related Content

What's hot (20)

Similar to Control structure of c (20)

More from Komal Kotak (6)

Recently uploaded (20)

Control structure of c