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.