Multiplication, Division and Modulo

Multiplication Operator

The multiplication operator * yields the product of its operands. For instance, if you're trying to determine the amount of water required to fill a pool:

Main


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#include <stdio.h>

int main()
{
	int height = 2; // in meters
	int width = 7; // in meters
	int length = 10; // in meters
	
	// A cubic meter contains one thousand liters

	int liters = (height * width * length) * 1000;

	printf("Size of pool: %d liters", liters);

	return 0;
}

Division Operator

The division operator / divides the left operand by the right one.

Suppose you want to calculate a car's speed:

Main


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#include <stdio.h>

int main()
{
	int s = 200; // in meters
	double t = 3; // three hours
	double v = s / t;

	printf("Velocity =  %f m/h", v);

	return 0;
}

Using double variables ensures our result can be a decimal value, providing a more accurate answer. If we only worked with integer types, the result would also be an integer:

Main


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#include <stdio.h>

int main()
{
	int s = 200; // in meters
	int t = 3;   // three hours
	// without `double v` variable

	printf("Velocity =  %d m/h", s/t); 

	return 0;
}

It's important to note that merely changing the format specifier won't fix an incorrect integer division:

Main


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#include <stdio.h>

int main()
{
	int s = 200; // in meters
	int t = 3; // three hours

	printf("Velocity =  %f m/h", s/t); // changed specifier

	return 0;
}

However, there's a way to get a correct division without introducing another variable:

Main


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#include <stdio.h>

int main()
{
	int s = 200; // in meters
	double t = 3; // three hours

	printf("Velocity =  %f m/h", s/t); // changed specificator

	return 0;
}

Note
For a division to yield a decimal result, at least one of the operands should be of a decimal type like double.

Modulo Operator

The % operator returns the remainder of a division. For instance:

Main


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#include <stdio.h>

int main()
{
	printf("Modulo 8 %% 5 = %d\n", 8 % 5); 
	printf("Modulo 10 %% 3 = %d\n", 10 % 3);
	printf("Modulo 7 %% 5 = %d\n", 7 % 5);
	printf("Modulo 20 %% 5 = %d\n", 20 % 5);

	return 0;
}

Note
If you're trying to display the % character in a string (e.g., in a printf statement), you'd use %% to represent a single %. This tells the compiler you want to print the % character and not use it as a format specifier.

Everything was clear?

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Section 3. Chapter 3