C Tutorial - Type Conversion or Modifier

Type modifier

The basic data types may have modifier preceding them to indicate special properties of the object being declared.

These modifiers change the meaning of the basic data types to suit the specific needs.

These modifiers are unsigned, signed, long and short. It is also possible to give these modifiers in combination, e.g., unsigned long int.

eg:-

Modifier for char Data Type

main()

{

char ch=291;

printf("%d\t%c\n",ch,ch);

}

output:- 35

Here ch has been defined as a char ,and char cannot take a value bigger than +128.That is why assigned value of ch is 291 and is considered to be 35 (291-128-128).

Data type Range Bytes occupied Format signed char -128 to +127 1 %c unsigned char 0 to 255 1 %c short signed int -32768 to 32767 2 %d short unsigned int 0 to 65535 2 %u long signed int -2147483648 to +2147483647 4 %ld long unsigned int 0 to 4294967295 4 %lu float -3.4e38 to 3.4e38 4 %f double -1.7e4932 to +1.7e308 8 %lf long double -1.7e4932 to 1.7e4932 10 %lf

Evaluation of expression

An expression is a combination of variables, constants and operators arranged according to the syntax of the language.

C can handle any complex expression with ease.

It is little bit different from algebraic expression.

Algebraic Expressions C Expressions axb-cxd a*b-c*d (m+n)(a+b) (m+n)*(a+b)

Evaluation of expression:

We can evaluate an expression by using assignment statement. As

Variable = Expression.

e.g. :

Temp = ((f * cos(x)/sin (y))+(g * sin(x)/cos(y)))

All relevant variables must be assigned values before the evaluation of the expression.

Type conversion in expression:

To effectively develop C programs, it would be necessary for you to understand the rules that are used for the implicit conversion of operands.

If an expression contains an operation between an int and a float, the int would be automatically promoted to a float before carrying out of operation.

Automatic type conversion

If the operands are of different types the lower type is automatically converted to the higher typebefore 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.

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*/

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