An if statement can be followed by an optional else statement, which executes when the booleanexpression is false.
Syntax:
The syntax of an if...else statement in C++ is:
if(boolean_expression) { // statement(s) will execute if the boolean expression is true } else { // statement(s) will execute if the boolean expression is false }
If the boolean expression evaluates to true, then the if block of code will be executed, otherwise else block of code will be executed.
Flow Diagram:
Example:
#include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a < 20 ) { // if condition is true then print the following cout << "a is less than 20;" << endl; } else { // if condition is false then print the following cout << "a is not less than 20;" << endl; } cout << "value of a is : " << a << endl; return 0; }
When the above code is compiled and executed, it produces the following result:
a is not less than 20; value of a is : 100
The if...else if...else Statement:
An if statement can be followed by an optional else if...else statement, which is very usefull to testvarious conditions using single if...else if statement.
When using if , else if , else statements there are few points to keep in mind.
- An if can have zero or one else's and it must come after any else if's.
- An if can have zero to many else if's and they must come before the else.
- Once an else if succeeds, none of he remaining else if's or else's will be tested.
Syntax:
The syntax of an if...else if...else statement in C++ is:
if(boolean_expression 1) { // Executes when the boolean expression 1 is true } else if( boolean_expression 2) { // Executes when the boolean expression 2 is true } else if( boolean_expression 3) { // Executes when the boolean expression 3 is true } else { // executes when the none of the above condition is true. }
Example:
#include <iostream> using namespace std; int main () { // local variable declaration: int a = 100; // check the boolean condition if( a == 10 ) { // if condition is true then print the following cout << "Value of a is 10" << endl; } else if( a == 20 ) { // if else if condition is true cout << "Value of a is 20" << endl; } else if( a == 30 ) { // if else if condition is true cout << "Value of a is 30" << endl; } else { // if none of the conditions is true cout << "Value of a is not matching" << endl; } cout << "Exact value of a is : " << a << endl; return 0; }
When the above code is compiled and executed, it produces the following result:
Value of a is not matching Exact value of a is : 100
0 comments:
Post a Comment