22. ISO C Standard Consideration

Q 22.1

Terminology

Answer

access

<execution-time action> to read or to modify the value of an object.

Note 1

Where only one of these two actions is meant, “read” or “modify” is used.

Note 2

“Modify” includes the case where the new value being stored is the same as the previous value.

Note 3

Expressions that are not evaluated do not access object.

alignment

requirement that objects of a particular type be located on storage boundaries with addresses that are particular multiples of a byte address

argument

actual argument or actual parameter(deprecated). expression in the comma-separated list bounded by the parentheses in a function call expression, or a sequence of preprocessing tokens in the comma-separated list bounded by the parentheses in a function-like macro invocation.

behavior

external appeareance or action

implementation-defined behavior

unspecified behavior where each implementation documents how the choice is made.

Example

An example of implementation-defined behavior is the propagation of the high-order bit when a signed integer is shifted right.

locale-specific behavior

behavior that depends on local conventions of nationality, culture, and language that each implementation documents.

Example

An example of locale-specific behavior is whether the islower function returns true for characters other than the 26 lowercase Latin characters.

undefined behavior

Behavior, upon use of a nonportable or erroneous program construct or of erroneous data, for which this International Standard imposes no requirements.

Note

Possible undefined behavior ranges from ignoring the situation completely with unpredictable results, to behaving during translation or program execution in a documented manner characteristic of the environment (with or without the issuance of a diagnostic message), to terminating a translation or execution (with the issuance of a diagnostic message).

Example

An example of undefined behavior is the behavior on integer overflow.

unspecified behavior

Behavior where this International Standard provides two or more possibilities and imposes no further requirements on which is chosen in any instance.

Example

An example of unspecified behavior is the order in which the arguments to a function are evaluated.

bit

Unit of data storage in the execution environment large enough to hold an object that may have one of two values.

Note

It need not be possible to express the address of each individual bit of an object.

byte

addressable unit of data storage large enough to hold any member of the basic character set of the execution environment. NOTE 1 It is possible to express the address of each individual byte of an object uniquely. NOTE 2 A byte is composed of a contiguous sequence of bits, the number of which is implementation-defined. The least significant bit is called the low-order bit; the most significant bit is called the high-order bit.

character

<abstract> member of a set of elements used for the organization, control, or representation of data

character

single-byte character <C> $<$C$>$ bit representation that fits in a byte

multibyte character

sequence of one or more bytes representing a member of the extended chracter set of either the source or the execution environment.

NOTE

The extended character set is a superset of the basic character set.