Atari ST series Technical Reference Manual page 410

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P o i n t s t o th e f ir s t b y t e p a s t t h e l o w R A M a r e a u s e d b y T O S . T h is is u s e d
f o r t h e s t a r t i n g a d d r e s s o f t h e T P A (e n d _ _ o s is c o p i e d i n t o _ _ m e m b o t ) .
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T h is p o i n t s t o t h e o p e r a t i n g s y s t e m c o m m a n d s h e ll w h i c h is e x e c u t e d
w h e n s y s t e m in iti a liz a ti o n is c o m p l e t e . N o r m a l l y , th is p o i n t s t o t h e f ir s t
b y t e o f t h e A E S t e x t s e g m e n t .
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T h e S c r d u m p ( ) r o u t i n e is v e c t o r e d t h r o u g h th is l o c a t i o n , s o t h a t w h e n
S c r d u m p ( ) is c a l l e d , o r t h e A l t e r n a t e - H e l p k e y s a r e p r e s s e d , p r o g r a m e x e ­
c u t i o n is d i r e c t e d to t h e r o u t i n e w h o s e a d d r e s s is f o u n d h e r e . T o i n s t a ll a
p r i n t e r d r i v e r f o r a n o t h e r p r i n t e r , t h e r e f o r e , a ll y o u h a v e to d o is t o lo a d
t h e n e w s c r e e n p r i n t p r o g r a m a s a t e r m i n a t e - a n d - s t a y - r e s i d e n t p r o g r a m
( s e e P t e r m r e s ( ) , C h a p t e r 5 ) , a n d s t o r e it s a d d r e s s h e r e .
T h is v e c t o r c a n a l s o b e d i v e r t e d f o r o t h e r p u r p o s e s . S o m e " s n a p s h o t "
p r o g r a m s , f o r e x a m p l e , u s e th is v e c t o r to in s t a ll a r o u t i n e t h a t s a v e s t h e
s c r e e n p i c t u r e to a a i s k file w h e n t h e A l t e m a t e - H e l p k e y s a r e p r e s s e d ,
r a t h e r t h a n s e n d i n g it to a p r i n t e r . I t 's a l s o p o s s ib le t o in s t a ll a s h o r t r o u ­
tin e t h a t t e s t s f o r s n if t k e y s w h e n A l t e m a t e - H e l p is p r e s s e d , t h u s a ll o w in g
a d d i t i o n a l h o t - k e y p r o g r a m s t o b e in s t a l l e d , r a t h e r t h a n j u s t r e p l a c i n g t h e
s c r e e n p r i n t f u n c t i o n .
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T h is v e c t o r is u s e d b y P r t b l k ( ) t o c a ll t h e P R N : d e v i c e o u t p u t s t a t u s r o u ­
tin e .
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T h is v e c t o r is u s e d b y P r t b l k ( ) t o c a ll t h e P R N : d e v i c e o u t p u t r o u t i n e .
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T h is v e c t o r is u s e d b y P r t b l k ( ) t o c a ll t h e A U X : d e v i c e o u t p u t s t a t u s r o u ­
tin e .
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T h is v e c t o r is u s e d b y P r t b l k ( ) t o c a ll t h e A U X : d e v i c e o u t p u t r o u t i n e .
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APPENDIX K
end__os
exec__os
scr_dump
prv__Isto
prv__1st
prv__auxo
prv__aux
($4FA-$4FD)
($4FE-$501)
($502-$505)
($506-$509)
($50A-$50D)
($50E-$511)
($512-$515)