If-else Operator

if-else

The if-else statement is a staple in programming. It enables you to direct the flow of your program based on certain conditions.

Note

Just a heads-up! Code blocks { } were introduced in Section 1, Chapter 2.

The if-else structure is pretty straightforward:


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if (condition) 
{
    // Execute this block of code if condition is true
}
else
{
    // Execute this block of code if condition is false
}

Take, for instance, the temperature variable that receives data from a temperature sensor.

Suppose we want a program that alerts us when the temperature gets too high:

Main.c

#include <stdio.h>

int main()

{

int temperature = 200; // in celsius

if (temperature > 80)

{

printf("Temperature is so high: %d degrees Celsius\n", temperature);

}

else

{

printf("Temperature is normal: %d degrees Celsius\n", temperature);

}

return 0;

}


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#include <stdio.h>

int main()
{
	int temperature = 200; // in celsius

	if (temperature > 80) 
	{
		printf("Temperature is so high: %d degrees Celsius\n", temperature);
	}

	else
	{
		printf("Temperature is normal: %d degrees Celsius\n", temperature);
	}

	return 0;
}

You can incorporate multiple if statements in a program, especially when you need to evaluate various conditions.

Note

Conditions can also include logical operators.

Else If

The if-else statement can be further expanded with else-if:

Main.c

#include <stdio.h>

int main()

{

int tempereture = 50; // in celsius

if (tempereture > 50) // condition 1

{

printf("Temperature is high: %d degrees Celsius\n", tempereture); // instruction_1

}

else if (tempereture > 100)// condition 2

{

printf("Temperature is so high: %d degrees Celsius\n", tempereture);// instruction_2

}

else if (tempereture > 150)// condition 3

{

printf("Temperature is critically high: %d degrees Celsius\n", tempereture);// instruction_3

}

else

{

printf("Temperature is normal: %d degrees Celsius\n", tempereture); // instruction_4

}

return 0;

}


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#include <stdio.h>

int main()
{
	int tempereture = 50; // in celsius

	if (tempereture > 50) // condition 1
	{
		printf("Temperature is high: %d degrees Celsius\n", tempereture); // instruction_1
	}

	else if (tempereture > 100)// condition 2
	{
		printf("Temperature is so high: %d degrees Celsius\n", tempereture);// instruction_2
	}

	else if (tempereture > 150)// condition 3
	{
		printf("Temperature is critically high: %d degrees Celsius\n", tempereture);// instruction_3
	}

	else
	{
		printf("Temperature is normal: %d degrees Celsius\n", tempereture); // instruction_4
	}

	return 0;
}

1. What is the purpose of an if-else statement in programming?

2. What is a basic structure of an if-else statement in C, including the syntax for code blocks.

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