Table of Contents

About

Float64 is a floating point number with a 64bit precision.

Float64 is also known as:

  • 64-bit floating-point values,
  • double precision floating-point
  • 64-bit IEEE-754 floating-point
  • or just double

It is a number bit representation that permits to store/manipulate:

in a computer

It's a logical data type. While your variable may have a float64 data type, the language engine will not store numbers in Float64 all the time because it will be terribly inefficient on a storage level.

Language

  • C: double. (implemented as a 64-bit IEEE 754 number, which uses 52 bits of space for the mantissa)
  • Java: double

Characteristic

Storage

Storing numbers in Float64 would be terribly inefficient

Example: The integer number 42 in bit representation

representation bit
Float 64 0100 0000 0100 0101 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000
Others
two’s complement 8-bit 0010 1010
two’s complement 32-bit 0000 0000 0000 0000 0000 0000 0010 1010
packed binary-coded decimal (BCD) 0100 0010
32-bit IEEE-754 floating-point 0100 0010 0010 1000 0000 0000 0000 0000

Max / Min

  • 53 bit is the maximum storage in Javascript
console.log(Number.MAX_SAFE_INTEGER); // 2^53 - 1
console.log(Number.MIN_SAFE_INTEGER); // (-(2^53 - 1)).
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Documentation / Reference