Difference between revisions of "C-and-Cpp/C2/If-And-Else-If-statement/English-USA"

To execute a single statement.

To execute group of statements.

We will do this through examples.

We will also see some common errors and their solutions.

Ubuntu Operating system version 11.10.

gcc and g++ Compiler version 4.6.1

A statement in a program controls the flow of program execution.

It helps to make decision on, what code is to be executed.

We can check the conditions, whether true or false.

We can execute a single statement or a group of statements.

Here, if the condition is true,then statement1 will be executed.

If the condition is false then statement2 will be executed.

Here, if condition1 is true then statement1 will be executed.

If condition1 is false then it will check for another condition that is condition2.

If condition2 is true, then statement3 will be executed.

If condition2 is false, then statement2 will be executed

I have already typed the code on the editor.

So let me open it.

Note that our filename is ifstmt.c

In this program we will calculate the sum of two numbers and will check a few conditions.

#include <stdio.h>

This is our header file.

int main()

{

int a, b, sum;

a, b and sum.

printf("Enter the value of a and b is \n");

scanf("%d%d",&a,&b);

User will enter the values of a and b.

The values will be stored in variable a and variable b.

scanf("%d%d",&a,&b);

It then stores the result in the given variable.

The format specifier in the scanf() helps to know the type of data.

Like here we have %d it denotes that we are dealing with integer data type.

sum=a+b;

We will store the result in sum.

printf("Sum of a and b is %d\n", c);

if(sum > 20)

{

printf("Sum is greater than20 \n");

}

Here, we check the condition whether sum is greater than 20.

If the condition is true,

then we print Sum is greater than 20.

/*

*/

return 0;

First we will see the execution of if statement.

Ctrl, Alt and T keys simultaneously on your keyboard.

gcc ifstmt.c -o if

gcc space ifstmt.c space -o space if And Press Enter

./if

./if Press Enter

Enter the value of a and b.

I will give the values as 10 and 12.

The output is displayed as

Sum of a and b is 22.

Sum is greater than 20.

Let me remove the comment from here.

I will give the comment here.

Now click on Save.

Here, we check another condition whether Sum is greater than 10.

If the condition is true.

Then we print Sum is greater than 10 and less than 20.

Let us compile as before.

Let us execute as before.

Enter the value of a and b.

I will give the values as 10 and 2.

The output is displayed as:

Sum of a and b is 12.

Sum is greater than 10 and less than 20.

Let me clear the prompt.

Now click on Save.

if(c > 20)

{

printf("Sum is greater than20 \n");

}

else if(c > 10)

{

printf("Sum is greater than 10 \n");

}

Highlight

else

{

printf("Sum is less than 10 \n");

}

This is our else statement.

Now let us execute and see.

Let us compile as before.

Let us execute as before.

Enter the value of a and b.

I will give the values as 3 and 5.

The output is displayed as, Sum of a and b is 8.

Sum is less than 10.

Come back to our program.

%d

Let see what will happen.

Come back to our terminal.

Let us compile as before.

else without a previous if

Come back to our program.

It is an syntax error.

If statement will never terminate with a semicolon.

And else if statement will never work without an if.

Delete the semicolon ; here

Come back to our terminal.

Let us execute as before.

Enter the value of a and b

I will give the values as 3 and 6.

The output is displayed as

Sum of a and b is 9.

Sum is less than 10.

Come back to our program.

Now save the file with an extension .cpp

and click on Save

<iostream>

iostream

using namespace std;

scanf()

Let us replace the printf() statement with the cout << statement.

Click on Replace all

and click on Close

Now delete the closing bracket here.

Replace the scanf statement with the cin statement.

Type cin >> and two closing angle brackets

As we use cin >> function to read a line in C++.

%d

Delete the comma and &

Delete the comma here and type two closing angle brackets.

Again delete the & and the closing brackets

Now Click on Save

<<

Now delete the (backslash) \n and format specifier

Now Type two opening brackets

Again type two opening angle brackets and within the double quotes type backslash<< “\n”.

Here also we will delete the closing bracket.

Now again delete the closing bracket here and here.

Let me clear the prompt. To compile type

g++ space ifstmt.cpp space -o space if1

Here we have if1 because we don't want to overwrite the output parameter if for the file ifstmt.c

Now Press Enter

To execute type

./if1

And Press Enter

Enter the value of a and b.

I will give the values as 20 and 10.

The output is displayed as,

Sum of a and b is 30.

Sum is greater than 20.

This brings us to the end of this tutorial.

Now come back to our slides.

In this tutorial we learned,

if statement

eg. if(condition)

{…........

} And

else if statement

eg. else if(condition)

{….........

}

Assignment

Write a program to check a is greater than b or less than b.

Hint:

use if statement.

Write another program to check which value is greater a, b or c.

Hint:

use else-if statement.

About the Spoken Tutorial Project

http://spoken-tutorial.org /What\_is\_a\_Spoken\_Tutorial

It summarizes the Spoken Tutorial project.

If you do not have good bandwidth, you can download and watch it.

Spoken Tutorial Workshops

Conducts workshops using spoken tutorials.

Gives certificates to those who pass an online test.

For more details, please write to,

contact@spoken hyphen tutorial dot org.

Acknowledgement

It is supported by the National Mission on Education through ICT, MHRD, Government of India.

More information on this Mission is available at the link shown below.

(http://spoken-tutorial.org\NMEICT-Intro)

Thank You for watching.