If
statements in C++
The
ability to control the flow of your program, letting it make decisions on what
code to execute, is valuable to the programmer. The if statement allows you to
control if a program enters a section of code or not based on whether a given
condition is true or false. One of the important functions of the if statement
is that it allows the program to select an action based upon the user's input.
For example, by using an if statement to check a user entered password, your
program can decide whether a user is allowed access to the program.
Syntax
if ( TRUE )
Execute the next statement
if ( 5 < 10 )
cout<<"Five is now less than ten, that's a big surprise";
C++ if...else statement
An if statement can be followed by an optional else statement, which executes when the boolean expression is false.
Syntax:
if(boolean_expression)
{
// statement(s) will execute if the boolean expression is true
}
else
{
// statement(s) will execute if the boolean expression is false
}
Example:
#include<iostream>
usingnamespacestd;
int main()
{string answer;cout<<"Please enter the password: ";
cin>>answer;cin.ignore();if(answer =='wrox') {
cout<<"You have successfully logged in";
}else {
cout<<"Wrong Password";
}cin.get();}
Switch statement
A switch statement allows a variable to be tested for equality against a list of values. Each value is called a case, and the variable being switched on is checked for each case.
Syntax:
switch(expression){
case constant-expression :
statement(s);
break; //optional
case constant-expression :
statement(s);
break; //optional
// you can have any number of case statements.
default : //Optional
statement(s);
}
Example:
#include <iostream>
using namespace std;
int main ()
{
// local variable declaration:
char grade = 'D';
switch(grade)
{
case 'A' :
cout << "Excellent!" << endl;
break;
case 'B' :
case 'C' :
cout << "Well done" << endl;
break;
case 'D' :
cout << "You passed" << endl;
break;
case 'F' :
cout << "Better try again" << endl;
break;
default :
cout << "Invalid grade" << endl;
}
cout << "Your grade is " << grade << endl;
return 0;
}
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