Note: This API calls are shared between DOS and Win16 personality.
DOSSHELL is a stripped down version of 16-bit Windows. Some APIs shared and same. DOSSHELL uses older version of API, but Win16 has more advanced APIs.
GRB is a plain binary file with 0 offset. Entry table is stable and not changed. Application must check address 015h for short jump opcode. If opcode is valid then assume interface is here.
Note: This API used by video device driver files with GRB extension. Used by DOSSWAP.EXE under DOS and by WINOLDAP.MOD under Windows to grab and restore screen
During setup GRB file will be renamed to WINOLDAP.GRB or DOSSHELL.GRB