Floating point constant in C language

Floating point constant

Definition: The numeric values having fractional part are called floating point constants. All  negative Numbers should have prefix ‘- ’. A positive number may have a ‘+’ sign that is optional. Other
Character  are not allowed . The floating point constant can be represented using two forms as:

1. Fractional form
2. Exponent notation(Scientific notation)

Fractional from: Now, let us see  ‘‘how to represent floating point numbers using fractional form?  Explain giving examples.’’ A floating point number represented using fractional form has an integer part followed by a decimal point and a fractional part. We can omit the digits before the decimal point or after the decimal point. For example, 0.5, -0.99, -6, -9,+.9 etc all are valid floating point numbers.

Exponent notation (Scientific notation): Now , the question is ‘‘How to represent floating point numbers in scientific notation? Give examples.’’ The floating point number represented using Scientific notation (also called exponential notation) has three parts namely:
                          (part1)             (part2)                 (Part 3)
                         mantissa             e or E                  exponent

  • The mantissa can be an integer or a floating point number represented using fractional Notation.The letter e or should follow mantissa.
  • The exponent should follow e or E. The exponent has to be an integer ‘‘with optional ‘+’
  • Sign’’ or ‘- ’ sign.

The following table shows invalid floating point numbers. The reasons for invalidity are also shown:

Floating point/ Real Constant
Valid / invalid
Reasons for invalidity
/ is not allowed.
There is no decimal point.
6.5e 8
White space is not allowed between e and 8.
More than one decimal point is not allowed.
Comma is not allowed
Fractional part 6.9 is not allowed in exponent part.


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