# Computer Number - Float64 (64-bit or double precision) floating-point number

## 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)).```
```

## Documentation / Reference

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