Expressions

Automatic type conversion

If the operands are of different types the lower type is automatically converted to the higher type before the operation proceeds

The result is of the higher type

Given below is the sequence of rules that are applied by evaluating expressions.

Operator 1 Operator 2 Result Long Double any Long Double Double any Double Float any Float Unsigned Long Int any Unsigned Long In Long Int any Long Int Unsigned Int any Unsigned Int

Final result of an expression to the type of the variable on the left of the assignment signed before assigning the value to it.

However, the following changes are introduced during the final assignment:

1. Float to Int causes truncation of the fractional part.

2. Double to float causes rounding of digits.

3. Long int to int causes dropping of the excess higher order bits

Type Casting:

Casting a value is a forcing a type conversion in a way that is different from the automatic conversion and this process is called type cast.

This should be clear from the following examples:

An example of automatic conversion:

Output of automatic conversion:

The answer turns out to be 1.000000 and not 1.5 this is because, 6 and 4 are both integers, and hence 6/4 yields an integer, 1.

This 1 when stored in a is converted to 1.000000. But what if you don't want the question to be truncated. One solution is to make either x or y as a float.

The general form of casting is:

(type_desired) expression;

where type_desired : standard C data types and

expression: constant, variables or an expression.

An example of type casting:

Output of type casting example:

Type Definition using typedef

C allows us to create data types via the typedef statement.

The format of typedef statement is:

typedef data type new_type_name;

Example:

typedef int units;

units bat1,bat2; /*this statement is equivalent to int bat1,bat2*/