Type Conversion in C

A type cast is basically a conversion from one type to another. There are two types of type conversion:

  1. Implicit Type Conversion Also known as ‘automatic type conversion’.
    • Done by the compiler on its own, without any external trigger from the user.
    • Generally takes place when in an expression more than one data type is present. In such condition type conversion (type promotion) takes place to avoid lose of data.
    • All the data types of the variables are upgraded to the data type of the variable with largest data type.
             bool -> char -> short int -> int -> 
             unsigned int -> long -> unsigned -> 
             long long -> float -> double -> long double
    • It is possible for implicit conversions to lose information, signs can be lost (when signed is implicitly converted to unsigned), and overflow can occur (when long long is implicitly converted to float).

    Example of Type Implicit Conversion:

    // An example of implicit conversion
    int main()
        int x = 10;    // integer x
        char y = 'a'// character c
        // y implicitly converted to int. ASCII 
        // value of 'a' is 97
        x = x + y;
        // x is implicitly converted to float
        float z = x + 1.0;
        printf("x = %d, z = %f", x, z);
        return 0;


    x = 107, z = 108.000000
  1. Explicit Type Conversion– This process is also called type casting and it is user defined. Here the user can type cast the result to make it of a particular data type.

    The syntax in C:

    (type) expression

    Type indicated the data type to which the final result is converted.

    // C program to demonstrate explicit type casting
    int main()
        double x = 1.2;
        // Explicit conversion from double to int
        int sum = (int)x + 1;
        printf("sum = %d", sum);
        return 0;


    sum = 2

    Advantages of Type Conversion

    • This is done to take advantage of certain features of type hierarchies or type representations.
    • It helps us to compute expressions containing variables of different data types.

Related articles:
Catch Block and Type Casting in C
Integer Promotion

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