In OS/2 2.1, the number of kilobytes in high memory is a DWORD field. Previous versions of the OS/2 operating system used a WORD field. Applications should query the version of the OS/2 operating system to determine the size of the data packet required. This query can be done by issuing an OEMHELP category 80h Function 00h or a DevHlp_GetDosVar with index=1, querying the MajorVersion and MinorVersion.