BS ISO/IEC 10967-1:2012

This standard BS ISO/IEC 10967-1:2012 Information technology. Language independent arithmetic is classified in these ICS categories:

• 35.060 Languages used in information technology

This part of ISO/IEC 10967 specifies properties of many of the integer and floating point datatypes available in a variety of programming languages in common use for mathematical and numerical applications.

It is not the purpose of this part of ISO/IEC 10967 to ensure that an arbitrary numerical function can be so encoded as to produce acceptable results on all conforming datatypes. Rather, the goal is to ensure that the properties of the arithmetic on a conforming datatype are made available to the programmer. Therefore, it is not reasonable to demand that a substantive piece of software run on every implementation that can claim conformity to this part of ISO/IEC 10967.

An implementor may choose any combination of hardware and software support to meet the specifications of this part of ISO/IEC 10967. It is the datatypes and operations on values of those datatypes, of the computing environment as seen by the programmer/user, that does or does not conform to the specifications.

The term implementation (of this part of ISO/IEC 10967) denotes the total computing environment pertinent to this part of ISO/IEC 10967, including hardware, language processors, subroutine libraries, exception handling facilities, other software, and documentation.

1.1 Inclusions

This part of ISO/IEC 10967 provides specifications for properties of integer and floating point datatypes as well as basic operations on values of these datatypes. Specifications are included for bounded and unbounded integer datatypes, as well as floating point datatypes. Boundaries for the occurrence of exceptions and the maximum error allowed are prescribed for each specified operation. Also the result produced by giving a special value operand, such as an infinity or a NaN (not-a-number), is prescribed for each specified floating point operation.

This part of ISO/IEC 10967 provides specifications for:

1. The set of required values of the arithmetic datatype.

2. A number of arithmetic operations, including:

   1. comparison operations on two operands of the same type,

   2. primitive operations (addition, subtraction, etc.) with operands of the same type,

   3. operations that access properties of individual values,

   4. conversion operations of a value from one arithmetic datatype to another arithmetic datatype, where at least one of the datatypes is conforming to this part of ISO/IEC 10967, and

   5. numerals for all values specified by this part of ISO/IEC 10967 for a conforming datatype.

This part of ISO/IEC 10967 also provides specifications for:

1. The results produced by an included floating point operation when one or more argument values are IEC 60559 special values.

2. Program-visible parameters that characterise the values and certain aspects of the operations of an arithmetic datatype.

3. Methods for reporting arithmetic exceptions.

1.2 Exclusions

This part of ISO/IEC 10967 provides no specifications for:

1. Arithmetic and comparison operations whose operands are of more than one datatype. This part of ISO/IEC 10967 neither requires nor excludes the presence of such "mixed operand" operations.

2. An interval datatype, or the operations on such data. This part of ISO/IEC 10967 neither requires nor excludes such data or operations.

3. A fixed point datatype, or the operations on such data. This part of ISO/IEC 10967 neither requires nor excludes such data or operations.

4. A rational datatype, or the operations on such data. This part of ISO/IEC 10967 neither requires nor excludes such data or operations.

5. The properties of arithmetic datatypes that are not related to the numerical process, such as the representation of values on physical media.

6. The properties of integer and floating point datatypes that properly belong in programming language standards or other specifications. Examples include:

   1. the syntax of numerals and expressions in the programming language, including the precedence of operators in the programming language,

   2. the syntax used for parsed (input) or generated (output) character string forms for numerals by any specific programming language or library,

   3. the presence or absence of automatic datatype coercions, and the consequences of applying an operation to values of improper type, or to uninitialised data,

   4. the rules for assignment, parameter passing, and returning value.

      NOTE — See Clause 7 and Annex D for a discussion of language standards and language bindings.

The internal representation of values is beyond the scope of this standard. E.g., the value of the exponent bias, if any, is not specified, nor available as a parameter specified by this part of ISO/IEC 10967. Internal representations need not be unique, nor is there a requirement for identifiable fields (for sign, exponent, and so on).

Furthermore, this part of ISO/IEC 10967 does not provide specifications for how the operations should be implemented or which algorithms are to be used for the various operations.