Update get-pgmptr.md

Mention entry point restriction on calling _get_pgmptr

Author: Steve Wishnousky

docs/c-runtime-library/reference/get-pgmptr.md

@@ -38,7 +38,7 @@ errno_t _get_pgmptr( 
  Returns zero if successful; an error code on failure. If `pValue` is `NULL`, the invalid parameter handler is invoked as described in [Parameter Validation](../../c-runtime-library/parameter-validation.md). If execution is allowed to continue, this function sets `errno` to `EINVAL` and returns `EINVAL`.  
 
 ## Remarks  
- The `_pgmptr` global variable contains the full path to the executable associated with the process. For more information, see [_pgmptr, _wpgmptr](../../c-runtime-library/pgmptr-wpgmptr.md).  
+ Only call `_get_pgmptr` if your program has a narrow entry point, like `main()` or `WinMain()`. The `_pgmptr` global variable contains the full path to the executable associated with the process. For more information, see [_pgmptr, _wpgmptr](../../c-runtime-library/pgmptr-wpgmptr.md).  
 
 ## Requirements  
 
@@ -49,4 +49,4 @@ errno_t _get_pgmptr( 
  For more compatibility information, see [Compatibility](../../c-runtime-library/compatibility.md) in the Introduction.  
 
 ## See Also  
- [_get_wpgmptr](../../c-runtime-library/reference/get-wpgmptr.md)
+ [_get_wpgmptr](../../c-runtime-library/reference/get-wpgmptr.md)