Pragma directives
A pragma is an implementation-defined instruction
to the compiler. It has the general form:
The character_sequence is a series of characters
giving a specific compiler instruction and arguments, if any. The
token
STDC indicates a standard pragma; consequently,
no macro substitution takes place on the directive. The new-line character
must terminate a pragma directive.The character_sequence on a pragma is not subject to macro substitutions.
Note: 
You can also use the 
You can also use the _Pragma operator
syntax to specify a pragma directive; for details, see The _Pragma preprocessing operator. More than one pragma construct can be specified on a single pragma directive. The compiler ignores unrecognized pragmas.
Standard C pragmas are described in Standard pragmas. 
Pragmas available for z/OS® XL
C/C++ are described in z/OS XL C/C++ pragmas. 