C Num Type Conversion

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Type Conversion

Sometimes, you have to convert the value of one data type to another type. This is known as C Type Conversion.

For example, if you try to divide two integers, 5 by 2, you would expect the result to be 2.5. But since we are working with integers (and not floating-point values), the following example will just output 2:

Example:

int x = 5;  
int y = 2;  
int sum = 5 / 2;  
  
printf("%d", sum); // 

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There are two types of conversion in C:

• Implicit Conversion (automatically)

• Explicit Conversion (manually)

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Implicit Conversion

Implicit conversion is done automatically by the compiler when you assign a value of one type to another.

For example, if you assign an int value to a float type:

Example:

// Automatic conversion: int to float  
float myFloat = 9;  
  
printf("%f", myFloat); // 9.000000

As you can see, the compiler automatically converts the int value 9 to a float value of 9.000000.

Warning

Especially if it was the other way around - the following example automatically converts the float value 9.99 to an int value of 9:x

// Automatic conversion: float to int  
int myInt = 9.99;  
printf("%d", myInt); // 9

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Strange Case:

As another example, if you divide two integers: 5 by 2, you know that the sum is 2.5. And as you know from the beginning of this page, if you store the sum as an integer, the result will only display the number 2. Therefore, it would be better to store the sum as a float or a double, right?

Example:

float sum = 5 / 2;  
  
printf("%f", sum); // 2.000000
 

Why is the result 2.00000 and not 2.5? Well, it is because 5 and 2 are still integers in the division. In this case, you need to manually convert the integer values to floating-point values. (see below).

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Explicit Conversion (casting)

Explicit conversion is done manually by placing the type in parentheses () in front of the value.

Considering our problem from the example above, we can now get the right result:

// Manual conversion: int to float  
float sum = (float) 5 / 2;  
  
printf("%f", sum); // 2.500000

You can also place the type in front of a variable:

int num1 = 5;  
int num2 = 2;  
float sum = (float) num1 / num2;  
  
printf("%f", sum); // 2.500000