_Real can be used to stand for a real number in a pattern.
You can enter a floating-point number of any length.
You can enter a number in scientific notation by using the form mantissa*^exponent.
You can enter a floating-point number in base b using b^^digits. The base must be less than 36. The letters a-z or A-Z are used in sequence to stand for digits 10 through 35.
Real is also used to indicate an approximate real number in Read.
EXAMPLES
Basic Examples 
Scope 