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PERSON-DATA is defined as an alphanumeric data item that renames PERSON-REC, treating the data bytes continued within it as character data. 01 PERSON-REC . 05 PERSON-NAME . 10 PERSON-NAME-LAST PIC X(12) . 10 PERSON-NAME-FIRST PIC X(16) . 10 PERSON-NAME-MID PIC X . 05 PERSON-ID PIC 9(9) PACKED-DECIMAL . 01 PERSON-DATA RENAMES PERSON-REC .
A class in C++ is a user-defined type or data structure declared with any of the keywords class, struct or union (the first two are collectively referred to as non-union classes) that has data and functions (also called member variables and member functions) as its members whose access is governed by the three access specifiers private, protected or public.
C++ enforces stricter typing rules (no implicit violations of the static type system [1]), and initialization requirements (compile-time enforcement that in-scope variables do not have initialization subverted) [7] than C, and so some valid C code is invalid in C++. A rationale for these is provided in Annex C.1 of the ISO C++ standard.
The above rules also apply to all the base classes and to all non-static data members in the class hierarchy; It has no base classes of the same type as the first defined non-static data member; A class/struct/union is considered POD if it is trivial, standard-layout, and all of its non-static data members and base classes are PODs.
A bit field is declared as a structure (or union) member of type int, signed int, unsigned int, or _Bool, [note 4] following the member name by a colon (:) and the number of bits it should occupy. The total number of bits in a single bit field must not exceed the total number of bits in its declared type (this is allowed in C++ however, where ...
bool is_negative (float x) {union {int i; float d;} my_union; my_union. d = x; return my_union. i < 0;} Accessing my_union.i after most recently writing to the other member, my_union.d , is an allowed form of type-punning in C, [ 6 ] provided that the member read is not larger than the one whose value was set (otherwise the read has unspecified ...
CLASS words ideally would be a very short list of data types relevant to a particular application. Common CLASS words might be: NO (number), ID (identifier), TXT (text), AMT (amount), QTY (quantity), FL (flag), CD (code), W (work) and so forth. In practice, the available CLASS words would be a list of less than two dozen terms.
One advanced dialect of C, called Cyclone, has extensive built-in support for tagged unions. [1] The enum types in the Rust, Haxe, and Swift languages also work as tagged unions. The variant library from the Boost C++ Libraries demonstrated it was possible to implement a safe tagged union as a library in C++, visitable using function objects.