# 48-bit floating point

From NDWiki

**Norsk Data 48-bit floating point format:**

The NORD-10 and the ND-100 could use two different hardware floating point formats, either the 48-bit format described on this page, or alternatively ordered with 32-bit floating point hardware.

The ND-500 and ND-5000 used only the 32-bit floating point format for single precision, and 64-bit floating point as double precision. The ND-100 (or -110, -120) front ends in those systems would normally have come with the 32-bit option in order to be compatible with their 500(0) companion. The 48-bit format described on this page is only used by the 16-bit ND computers.

Field | #Bits | Purpose |
---|---|---|

bit 47 | 1 | Sign bit |

bit 46-32 | 15 | Exponent |

bit 31-0 | 32 | Mantissa |

- The mantissa is normalized: 0.5 ≤
*mantissa*< 1 - The mantissa has no implicit bit, unlike the 32-bit and 64-bit formats
- The decimal point is thus to the left of the 32th bit (before exponent is applied)
- The exponent has a bias of 2
^{14}, or 16384 (subtract 16384 to get true exponent)

**Special values**

- All 48 bits zero:
**Zero.** -
*(Any special value (e.g. -0) reprecenting floating point underflow is not documented in the ND-100 reference manual)*

**Precision**

- 32 bits or approximately 10 decimal digits

**Range**

- 2
^{-16384}- 0.5 ≤ X < 2^{16383}- 1 or X = 0

or

- approximately 10
^{-4920}< X < 10^{4920}

### Sources

- Norsk Data Document ND–06.014.02 ND-100 REFERENCE MANUAL