Misc/abrash-black-book
Watch
1
0
Fork
You've already forked abrash-black-book
 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Normal quotes

Browse source
This commit is contained in:
James Gregory 2013-12-30 18:34:31 +11:00
commit 18011c595a
352 changed files with 6040 additions and 6040 deletions
Download patch file Download diff file Expand all files Collapse all files

24
29-02.md
View file

@ -13,16 +13,16 @@
DISPLAYED_SCREEN_SIZE equ (640/8)*350 ;# of displayed bytes per plane in a
; hi-res graphics screen
;
stack segment para stack ‘STACK’
stack segment para stack ‘STACK'
db 512 dup (?)
stack ends
;
Data segment word ‘DATA’
Filename db ‘SNAPSHOT.SCR’,0 ;name of file we’re restoring from
ErrMsg1 db ‘*** Couldn’‘t open SNAPSHOT.SCR ***’,0dh,0ah,‘$’
ErrMsg2 db ‘*** Error reading from SNAPSHOT.SCR ***’,0dh,0ah,‘$’
WaitKeyMsg db 0dh, 0ah, ‘Done. Press any key to end...’,0dh,0ah,‘$’
Handle dw ? ;handle of file we’re restoring from
Data segment word ‘DATA'
Filename db ‘SNAPSHOT.SCR',0 ;name of file we're restoring from
ErrMsg1 db ‘*** Couldn'‘t open SNAPSHOT.SCR ***',0dh,0ah,‘$'
ErrMsg2 db ‘*** Error reading from SNAPSHOT.SCR ***',0dh,0ah,‘$'
WaitKeyMsg db 0dh, 0ah, ‘Done. Press any key to end...',0dh,0ah,‘$'
Handle dw ? ;handle of file we're restoring from
Plane db ? ;plane being written
Data ends
;
@ -45,7 +45,7 @@
sub al,al ;open for reading
int 21h
mov [Handle],ax ;save the handle
jnc RestoreTheScreen ;we’re ready to restore if no error
jnc RestoreTheScreen ;we're ready to restore if no error
mov ah,9 ;DOS print string function
mov dx,offset ErrMsg1
int 21h ;notify of the error
@ -131,11 +131,11 @@ Chapter 28 provides a detailed explanation of the differences between
the Read Map and Map Mask registers.
Screen saving and restoring is pretty simple, eh? There are a few
caveats, of course, but nothing serious. First, the adapter’s registers
caveats, of course, but nothing serious. First, the adapter's registers
must be programmed properly in order for screen saving and restoring to
work. For screen saving, you must be in read mode 0; if you’re in color
compare mode, there’s no telling what bit pattern you’ll save, but it
certainly won’t be the desired screen image. For screen restoring, you
work. For screen saving, you must be in read mode 0; if you're in color
compare mode, there's no telling what bit pattern you'll save, but it
certainly won't be the desired screen image. For screen restoring, you
must be in write mode 0, with the Bit Mask register set to 0FFH and Data
Rotate register set to 0 (no data rotation and the logical function set
to pass the data through unchanged).