Microsoft KB Archive/32058

Video Service Discrepancy in Microsoft Press Books ID Number: Q32058

3.2x 3.30 MS-DOS

Summary: In the Microsoft Press book “Advanced MS-DOS,” under “ROM BIOS Interrupt 10H function 09H” on Page 409, the replication factor is stated as producing valid results only for the current row and results are unpredictable if the replication factor exceeds the maximum column value for the display. The Microsoft Press book “The Peter Norton Programmer’s Guide to the IBM PC” states on Page 179 that in text mode, the duplicated characters will successfully wrap around; however, in graphics mode, the characters will not wrap around. This ROM BIOS service will work in both text and graphics modes. In text mode, the replicated characters will successfully wrap around on the display to the next row if a replication value exceeds the maximum column of the display. In graphics mode, replicated characters will successfully appear as long as the replication factor does not exceed the maximum column value of the display. If the replication factor does exceed the maximum column value, the results are unpredictable. Often, the characters will wrap around, but only at one scan line lower than the preceding row, destroying the appearance of both rows.