#pragma :- is a directive
As we know that each implementation of C andC++ support some faetures unique to its host machine or Operating system.
The #pragma directive offers a way for each compiler to offer machine and operating System specific faetures while retaining overall compatibility with the C and C++
pragmas are machine or Operating System specific by defination, and usually diffrent for every compiler.
Where to Use:-
1)pragmas can be used in conditional statements
2)pragmas can be used to provide new preprocessor funcationality
3)pragmas can be used to provide implementation-defined information to the compiler.