Constants: Real or Floating-point constant

Constants

Constants in C which does not change its value during the execution of a program

Real or Floating-point constant

A real constant is combination of a whole number followed by a decimal point and the fractional part. 

Example: 45.22 , 0.45 , -4.56 ,    .76 , 341.       

The Real or Floating-point constants can be written in two forms:

                    1.     Normal  or Fractional form          
                    2.      Exponential form

Express a Real constant in fractional form
                    A real constant consists for a series of digits representing the whole part of the number, followed by a decimal point, the decimal cannot be omitted.

Valid Real constants (Fractional):     -4.45     +645.916     0.0      5.
Invalid Real constant: -                      4          -          a decimal point is missing
                                                            1,3      -           Illegal character (,)

Rules for Constructing Real Constants in Fractional Form
1.    A real constant must have at least one digit.
2.    It must have a decimal point.
3.    It could be either +ve or -ve.
4.    Default sign is +ve.
5.    Commas or blanks are not allowed within a real constant.

Express a real constant in Exponential form

If the value of a constant is either too small or too large, exponential form of representation of real constants is usually used.

In exponential form, the real constant is represented in two parts.

               Mantissa - The part appearing before e, the mantissa is either a real number expressed in decimal notation or an integer.

                Exponent - The part following e, the exponent is an integer with an optional plus or minus sign followed by a series of digits. The letter e separating the                                                     mantissa and the exponent can be written in either lowercase or uppercase.

 

For Example – 54000000 we can write  54 x 10⁶    ---à  54E6
                                                       or      5.4 x 10⁷   ---à  5.4E7

                                                       or    0.54 x 10⁸    --à    0.54E8

Rules for Constructing Real Constants in Exponential Form

1.      The mantissa part and the exponential part should be separated by letter in

          exponential form
2.      The mantissa part may have a positive or negative sign.
3.      Default sign of mantissa part is positive.
4.      The exponent part must have at least one digit, which must be a positive

          or negative integer. Default sign is positive.

5.      Range of real constants expressed in exponential for is -3.4e38 to

          3.4e38.