Intel 64 and IA-32 Architectures Software Developers Manual Volume 1, Basic Architecture

4-14 Vol. 1

DATA TYPES

The packed BCD integer indefinite encoding (FFFFC000000000000000H) is stored by

the FBSTP instruction in response to a masked floating-point invalid-operation

exception. Attempting to load this value with the FBLD instruction produces an unde-

fined result.

4.8 REAL NUMBERS AND FLOATING-POINT FORMATS

This section describes how real numbers are represented in floating-point format in

x87 FPU and SSE/SSE2/SSE3 floating-point instructions. It also introduces terms

such as normalized numbers, denormalized numbers, biased exponents, signed

zeros, and NaNs. Readers who are already familiar with floating-point processing

techniques and the IEEE Standard 754 for Binary Floating-Point Arithmetic may wish

to skip this section.

Table 4-4. Packed Decimal Integer Encodings

Magnitude

Class Sign digit digit digit digit ... digit

Positive

Largest 0 0000000 1001 1001 1001 1001 ... 1001

.. .

Smallest 0 0000000 0000 0000 0000 0000 ... 0001

Zero 0 0000000 0000 0000 0000 0000 ... 0000

Negative

Zero 1 0000000 0000 0000 0000 0000 ... 0000

Smallest 1 0000000 0000 0000 0000 0000 ... 0001

.. .

Largest 1 0000000 1001 1001 1001 1001 ... 1001

Packed

BCD

Integer

Indefinit

1 1111111 1111 1111 1100 0000 ... 0000

← 1 byte →← 9 bytes →