Chapter 7. Low Level System Information

7.1. Machine Interface

7.1.1. Processor Architecture

The IA32 Architecture is specified by the following documents

Only the features of the Intel486 processor instruction set may be assumed to be present. An application should determine if any additional instruction set features are available before using those additional features. If a feature is not present, then a conforming application shall not use it.

Conforming applications may use only instructions which do not require elevated privileges.

Conforming applications shall not invoke the implementations underlying system call interface directly. The interfaces in the implementation base libraries shall be used instead.

Rationale: Implementation-supplied base libraries may use the system call interface but applications must not assume any particular operating system or kernel version is present.

Applications conforming to this specification shall provide feedback to the user if a feature that is required for correct execution of the application is not present. Applications conforming to this specification should attempt to execute in a diminished capacity if a required instruction set feature is not present.

This specification does not provide any performance guarantees of a conforming system. A system conforming to this specification may be implemented in either hardware or software.

7.1.2. Data Representation

LSB-conforming applications shall use the data representation as defined in Chapter 3 of the System V ABI, IA32 Supplement. Byte Ordering

LSB-conforming systems and applications shall use the bit and byte ordering rules specified in Section 1.3.1 of the Intel® Architecture Software Developer's Manual Volume 1. Fundamental Types

In addition to the fundamental types specified in Chapter 3 of the System V ABI, IA32 Supplement, a 64 bit data type is defined here.

Table 7-1. Scalar Types

TypeCsizeofAlignment (bytes)Intel386 Architecture
Integrallong long84signed double word
signed long long
unsigned long long84unsigned double word Aggregates and Unions

LSB-conforming implementations shall support aggregates and unions with alignment and padding as specified in Chapter 3 of the System V ABI, IA32 Supplement. Bit Fields

LSB-conforming implementations shall support structure and union definitions that include bit-fields as specified in Chapter 3 of the System V ABI, IA32 Supplement.