15 Jul
2012
15 Jul
'12
6:29 p.m.
At 05:57 PM 7/15/2012, Jerome H. Fine wrote:
How much memory is available for a program under OS/8?
VT support isn't available until the system has at least 16k of memory.
The OS takes up 256 words of that.
80x24 frame buffer including flags occupies a big chunk of that - 2048
words (which holds the current screen image plus video attributes). On
that 16k system, TECO is overlayed to make things fit. More memory
means that the overlays get remapped into different memory fields,
avoiding the swapping.
Making OS/8 TECO support bigger screens wouldn't be either practical or
useful as the current
As for "terminals" which have more than 24
lines and / or 132 columns,
even 40K bytes is not very much memory for a "terminal" with 100 lines
and 200 columns, but it is sufficient.
40K 8-bit bytes (what you're talking about here for just your screen
buffer) is roughly 26KW out of the maximum 32KW for an OS/8 system.
Doesn't leave much for code, does it? That's why it's either
impractical or so heavily overlayed that it wouldn't be usable.
-Rick