Type Conversion & Type Casting

Sometimes we have a value of one data type but need to use it as another data type.

For example, we may have an int but want to use it as a float.

C provides two ways to handle this:

1. Type Conversion

2. Type Casting

Type Conversion

Type conversion is the process of converting one data type into another automatically by the compiler.

For example:

int a = 10;
float b = a;

Here, a is an int, but it is automatically converted to float.

int 10
  ↓
float 10.0

This is called implicit type conversion.

Example

int a = 10;
float b = 3.5;

float result = a + b;

C automatically converts a from int to float before performing the addition.

Type Casting

Type casting is the process of manually converting a value from one data type to another using the programmer's instruction.

We use the following syntax:

(data_type) value

For example:

int a = 10;
float result = (float)a;

Here, (float) tells the compiler to treat a as a float.

Example with Division

Consider:

int a = 5;
int b = 2;

float result = a / b;

You might expect 2.5, but the result is 2.0 because both operands are integers, so integer division happens first.

To get 2.5, we can use type casting:

float result = (float)a / b;

Now a is converted to float, so floating-point division is performed.

5 / 2
 ↓
2.5

Type Conversion vs Type Casting

Simple Example

#include <stdio.h>

int main()
{
    int a = 5;
    int b = 2;

    printf("%d\n", a / b);
    printf("%f\n", (float)a / b);

    return 0;
}

Output:

2
2.500000

The first calculation uses integer division, while the second uses type casting to perform floating-point division.

One Important Point

When converting from a type with a larger range or precision to a smaller one, data may be lost.

For example:

float price = 99.99;
int value = (int)price;

Now value becomes:

99

The decimal part is discarded.

In Simple Words

Type conversion happens automatically, while type casting is done explicitly by the programmer.

A simple way to remember:

Conversion → Compiler does it

Casting → Programmer does it