Float and double both store fractional numbers
The size of float is 4 bytes while the size of double is 8 bytes. if we store an integer value in float it's in form 0.0 but in double it is 0.00
a fractional number by default has double data type. to explicitly specify we write it as 0.0f or 0.00d for float and double respectively.
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Float-The type float specifies a single-precision value that uses 32 bits of storage. Float width size is 32 bit.Float ranges from 3 .4e–038 to 3.4e+038

Double-The type double specifies a double precision value that uses 64 bits of storage.Double width size 64 bit.Double ranges from 
1 .7e–308 to 1.7e+308