Type Casting in C | My CS Tutorial

C - Type Casting | Type casting in c | Implicit, explicit | Type conversions in c | Example | Usual arithmetic conversion | Integer promotion | My CS Tutorial

Type casting in c | My CS Tutorial

In programming languages, if the expression contains two or more different datatypes values then they must be converted to the single data type of destination datatype. Here the destination is the location where the final result of that expression is stored.

For example, the multiplication of an integer data value with the float data value and storing the result into a float variable. In this case, the integer value must be converted to float value so that the final result is a float datatype value.

Type casting in C

Type casting is a way to convert a variable from one data type to another data type. For example, if you want to store a ‘long’ value into a simple integer, then you can type cast ‘long’ to ‘int’. You can convert the values from one type to another explicitly using the cast operator as follows:-

(type_name) expression

Consider the following example where the cast operator causes the division of
one integer variable by another to be performed as a floating-point operation:-

#include <stdio.h>
main()
{
 int sum = 27, count = 5;
 double mean;
 mean = (double) sum / count;
 printf("Value of mean : %f\n", mean );
}

When the above code is compiled and executed, it produces the following result:-

Value of mean : 5.400000

It should be noted here that the cast operator has precedence over division, so the value of sum is first converted to type double and finally it gets divided by count yielding a double value.

Type conversions

Type conversions can be implicit which is performed by the compiler
automatically, or it can be specified explicitly through the use of the cast
operator. It is considered good programming practice to use the cast operator whenever type conversions are necessary.

Integer Promotion

Integer promotion is the process by which values of integer type "smaller"
than int or unsigned int are converted either to int or unsigned int. Consider
an example of adding a character with an integer:-

#include <stdio.h>
main()
{
 int i = 17;
 char c = 'c'; /* ascii value is 99 */
 int sum;
 sum = i + c;
 printf("Value of sum : %d\n", sum );
}

When the above code is compiled and executed, it produces the following result:
Value of sum : 116

Here, the value of sum is 116 because the compiler is doing integer promotion
and converting the value of 'c' to ASCII before performing the actual addition
operation.

Usual Arithmetic Conversion

The usual arithmetic conversions are implicitly performed to cast their values
to a common type. The compiler first performs integer promotion; if the
operands still have different types, then they are converted to the type that
appears highest order. Datatypes converted from low data types to high datatypes like:

 int datatype in float datatype
 float datatype in double datatype

The usual arithmetic conversions are not performed for the assignment
operators, nor for the logical operators && and ||. Let us take the following
example to understand the concept:-

#include <stdio.h>
main()
{
 int i = 17;
 char c = 'c'; /* ascii value is 99 */
 float sum;
 sum = i + c;
 printf("Value of sum : %f\n", sum );
}

When the above code is compiled and executed, it produces the following result:
Value of sum : 116.000000

Here, it is simple to understand that first c gets converted to integer, but as the final value is double, usual arithmetic conversion applies and the compiler converts i and c into ‘float’ and adds them yielding a ‘float’ result.


C - Type Casting | Type casting in c | Implicit, explicit | Type conversions in c | Example | Usual arithmetic conversion | Integer promotion | My CS Tutorial

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