#pragma

Pragma is a Include Guards, it tells compiler whether to include header file again or not

#pragma was introduced to remove dependency on #ifdef for solely including header file.

// In myheader.h
#ifndef MYHEADER_H
#define MYHEADER_H

// Header contents go here

#endif // MYHEADER_H

Above, as we can see here we are using #ifndef for including header files only once, but here we need to declare a Macro = MYHEADER_H to chieve this.

To overcome this unnecessary creation of a Macro, we can use #pragma once which does the same thing without declaring any Macro.