Control structures allow to change the flow of execution sequence of a program.
C++ has two types of control structures
1. Decision or branching control structures
2. Looping or iterative control structures
Decision
or branching control structures
Conditional branching statements help to jump
from one part of the program to another depending on whether a particular
condition is satisfied or not..
In C++ we have the following Decision Control
Statements (or) Conditional Branching Statements
1. If statement.
2. If – else statement.
3. If—else – if statement.
4. Switch case statement.
1. IF statement:
If statement is the simplest form of
decision control statement. It is used frequently in decision making
Syntax:
If( Test
Expression)
{
Body of
the if;
}
Statement
x;
If the test expression is true the “body of
the if” will be executed, if it false control goes to the statements just below
the if block.
Example
program:
#include<iostream.h>
#include<conio.h>
{
Void main()
{
clrscr();
int age;
cout<<”enter your age \n”;
cin>>age;
if(age>=18)
Cout<<”you are eligible to vote”;
cout<<”not eligible to vote”;
getch();
}
2. IF-ELSE statement:
The If-Else statement is an extension of simple if Statement. It has additional block that is else-block (or) false block.
Example Program: To find the Biggest of Two numbers
#include<iostream.h>
#include<conio.h>
Void main()
{
clrscr();
int a=0,b=0;
cout<<”Enter a,b values…\n”;
cin>>a>>b;
if(a>b)
cout<<a<<” is big”;
else
cout<<b<<” is big”;
getch();
}
3. IF – Else- IF statement (Nested if) :
When a series of decisions are involved we may have to use more than one if else statement in nested form.
Syntax:
If (condition-1)
{
Statement block
1;
}
else if (
condition-2)
{
Statement block
2;
}
lse if( condition-n)
{
Statement
block-n;
}
Statement x;
4. Switch Case Statement: A switch in C++ checks for equating multiple values to the variable (or) expression given in the switch header.
If case result is true, the set of the statements written in that case are executed. The keyword “break” should be placed at the end of the statement block otherwise the control passes to the statements of next case and goes on executing till a break is encountered or the statements in the switch case or over.
Syntax:
switch(expression)
{
case value1 :
body1
break;
case value2 :
body2
break;
case value3 :
body3
break;
default :
default-body
break;
}
next-statement;
Example Program:
#include<iostream.h>
#include<conio.h>
void main()
{
clrscr();
char o;
float num1,num2;
cout<<"Select
an operator either + or - or * or / \n";
cin>>o;
cout<<"Enter
two values: ";
cin>>num1>>num2;
switch(o) {
case '+':
cout<<num1<<"
+ "<<num2<<" = "<<num1+num2;
break;
case '-':
cout<<num1<<"
- "<<num2<<" = "<<num1-num2; break;
case '*':
cout<<num1<<"
* "<<num2<<" = "<<num1*num2;
break;
case '/':
cout<<num1<<"
/ "<<num2<<" = "<<num1/num2;
break;
default:
/* If operator
is other than +, -, * or /, error message is shown */
cout<<"Error!
operator is not correct";
break;
}
getch();
}
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