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diff --git a/docs/os12/mdfs.net/Docs/Comp/BBC/OS1-20/E435 b/docs/os12/mdfs.net/Docs/Comp/BBC/OS1-20/E435
new file mode 100644
index 0000000..636b244
--- /dev/null
+++ b/docs/os12/mdfs.net/Docs/Comp/BBC/OS1-20/E435
@@ -0,0 +1 @@
+**************** BUFFER ADDRESS HI LOOK UP TABLE ************************
E435    DB      &03   ;keyboard
E436    DB      &0A   ;rs423 input
E437    DB      &08   ;rs423 output
E438    DB      &07   ;printer
E439    DB      &07   ;sound 0
E43A    DB      &07   ;sound 1
E43B    DB      &07   ;sound 2
E43C    DB      &07   ;sound 3
E43D    DB      &09   ;speech
 
**************** BUFFER ADDRESS LO LOOK UP TABLE ************************
E43E    DB      &00
E43F    DB      &00
E440    DB      &C0
E441    DB      &C0
E442    DB      &50
E443    DB      &60
E444    DB      &70
E445    DB      &80
E446    DB      &00
 
**************** BUFFER START ADDRESS OFFSET ****************************
E447    DB      &E0
E448    DB      &00
E449    DB      &40
E44A    DB      &C0
E44B    DB      &F0
E44C    DB      &F0
E44D    DB      &F0
E44E    DB      &F0
E44F    DB      &C0

*******: get nominal buffer addresses in &FA/B **************************

    	; ON ENTRY X=buffer number
    	;Buffer number  Address         Flag    Out pointer     In pointer
    	;0=Keyboard     3E0-3FF         2CF     2D8             2E1
    	;1=RS423 Input  A00-AFF         2D0     2D9             2E2
    	;2=RS423 output 900-9BF         2D1     2DA             2E3
    	;3=printer      880-8BF         2D2     2DB             2E4
    	;4=sound0       840-84F         2D3     2DC             2E5
    	;5=sound1       850-85F         2D4     2DD             2E6
    	;6=sound2       860-86F         2D5     2DE             2E7
    	;7=sound3       870-87F         2D6     2DF             2E8
    	;8=speech       8C0-8FF         2D7     2E0             2E9

E450	LDA &E43E,X ;get buffer base address lo
E453	STA &FA     ;store it
E455	LDA &E435,X ;get buffer base address hi
E458	STA &FB     ;store it
E45A	RTS         ;exit


*************************************************************************
*                                                                       *
*       OSBYTE 152 Examine Buffer status                                *
*                                                                       *
*************************************************************************
;on entry X = buffer number
;on exit FA/B points to buffer start  Y is offset to next character
;if buffer is empty C=1, Y is preserved else C=0

E45B	BIT &D9B7   ;set V and
E45E	BVS &E461   ;jump to E461


*************************************************************************
*                                                                       *
*       OSBYTE 145 Get byte from Buffer                                 *
*                                                                       *
*************************************************************************
;on entry X = buffer number
; ON EXIT Y is character extracted
;if buffer is empty C=1, else C=0

E460	CLV         ;clear V

E461	JMP (&022C) ;Jump via REMV


*************************************************************************
*                                                                       *
*       REMV buffer remove vector default entry point                   *
*                                                                       *
*************************************************************************
;on entry X = buffer number
;on exit if buffer is empty C=1, Y is preserved else C=0

E464	PHP         ;push flags
E465	SEI         ;bar interrupts
E466	LDA &02D8,X ;get output pointer for buffer X
E469	CMP &02E1,X ;compare to input pointer
E46C	BEQ &E4E0   ;if equal buffer is empty so E4E0 to exit
E46E	TAY         ;else A=Y
E46F	JSR &E450   ;and get buffer pointer into FA/B
E472	LDA (&FA),Y ;read byte from buffer
E474	BVS &E491   ;if V is set (on input) exit with CARRY clear
    	            ;Osbyte 152 has been done
E476	PHA         ;else must be osbyte 145 so save byte
E477	INY         ;increment Y
E478	TYA         ;A=Y
E479	BNE &E47E   ;if end of buffer not reached <>0 E47E

E47B	LDA &E447,X ;get pointer start from offset table

E47E	STA &02D8,X ;set buffer output pointer
E481	CPX #&02    ;if buffer is input (0 or 1)
E483	BCC &E48F   ;then E48F

E485	CMP &02E1,X ;else for output buffers compare with buffer start
E488	BNE &E48F   ;if not the same buffer is not empty so E48F

E48A	LDY #&00    ;buffer is empty so Y=0
E48C	JSR &E494   ;and enter EVENT routine to signal EVENT 0 buffer
    	            ;becoming empty

E48F	PLA         ;get back byte from buffer
E490	TAY         ;put it in Y
E491	PLP         ;get back flags
E492	CLC         ;clear carry to indicate success
E493	RTS         ;and exit




**************************************************************************
**************************************************************************
**                                                                      **
**      CAUSE AN EVENT                                                  **
**                                                                      **
**************************************************************************
**************************************************************************
;on entry Y=event number
;A and X may be significant Y=A, A=event no. when event generated @E4A1
;on exit carry clear indicates action has been taken else carry set

E494	PHP         ;push flags
E495	SEI         ;bar interrupts
E496	PHA         ;push A
E497	STA &FA     ;&FA=A
E499	LDA &02BF,Y ;get enable event flag
E49C	BEQ &E4DF   ;if 0 event is not enabled so exit
E49E	TYA         ;else A=Y
E49F	LDY &FA     ;Y=A
E4A1	JSR &F0A5   ;vector through &220
E4A4	PLA         ;get back A
E4A5	PLP         ;get back flags
E4A6	CLC         ;clear carry for success
E4A7	RTS         ;and exit


********* check event 2 character entering buffer ***********************

E4A8	TYA         ;A=Y
E4A9	LDY #&02    ;Y=2
E4AB	JSR &E494   ;check event
E4AE	TAY         ;Y=A


*************************************************************************
*                                                                       *
*       OSBYTE 138 Put byte into Buffer                                 *
*                                                                       *
*************************************************************************
;on entry X is buffer number, Y is character to be written


E4AF	TYA         ;A=Y

E4B0	JMP (&022A) ;jump to INSBV


*************************************************************************
*                                                                       *
*       INSBV insert character in buffer vector default entry point     *
*                                                                       *
*************************************************************************
;on entry X is buffer number, A is character to be written

E4B3	PHP         ;save flags
E4B4	SEI         ;bar interrupts
E4B5	PHA         ;save A
E4B6	LDY &02E1,X ;get buffer input pointer
E4B9	INY         ;increment Y
E4BA	BNE &E4BF   ;if Y=0 then buffer is full else E4BF
E4BC	LDY &E447,X ;get default buffer start

E4BF	TYA         ;put it in A
E4C0	CMP &02D8,X ;compare it with input pointer
E4C3	BEQ &E4D4   ;if equal buffer is full so E4D4
E4C5	LDY &02E1,X ;else get buffer end in Y
E4C8	STA &02E1,X ;and set it from A
E4CB	JSR &E450   ;and point &FA/B at it
E4CE	PLA         ;get back byte
E4CF	STA (&FA),Y ;store it in buffer
E4D1	PLP         ;pull flags
E4D2	CLC         ;clear carry for success
E4D3	RTS         ;and exit


E4D4	PLA         ;get back byte
E4D5	CPX #&02    ;if we are working on input buffer
E4D7	BCS &E4E0   ;then E4E0

E4D9	LDY #&01    ;else Y=1
E4DB	JSR &E494   ;to service input buffer full event
E4DE	PHA         ;push A


***** return with carry set *********************************************

E4DF	PLA         ;restore A

E4E0	PLP         ;restore flags
E4E1	SEC         ;set carry
E4E2	RTS         ;and exit



***************** CODE MODIFIER ROUTINE *********************************
*                 CHECK FOR ALPHA CHARACTER                             *
*************************************************************************
    	            ;ENTRY  character in A
    	            ;exit with carry set if non-Alpha character
E4E3	PHA         ;Save A
E4E4	AND #&DF    ;convert lower to upper case
E4E6	CMP #&41    ;is it 'A' or greater ??
E4E8	BCC &E4EE   ;if not exit routine with carry set
E4EA	CMP #&5B    ;is it less than 'Z'
E4EC	BCC &E4EF   ;if so exit with carry clear
E4EE	SEC         ;else clear carry
E4EF	PLA         ;get back original value of A
E4F0	RTS         ;and Return
    	            ;
    	            ;

*******: INSERT byte in Keyboard buffer *********************************

E4F1	LDX #&00    ;X=0 to indicate keyboard buffer

*************************************************************************
*                                                                       *
*       OSBYTE 153 Put byte in input Buffer checking for ESCAPE         *
*                                                                       *
*************************************************************************
;on entry X = buffer number (either 0 or 1)
;X=1 is RS423 input
;X=0 is Keyboard
;Y is character to be written

E4F3	TXA         ;A=buffer number
E4F4	AND &0245   ;and with RS423 mode (0 treat as keyboard
    	            ;1 ignore Escapes no events no soft keys)
E4F7	BNE &E4AF   ;so if RS423 buffer AND RS423 in normal mode (1) E4AF

E4F9	TYA         ;else Y=A character to write
E4FA	EOR &026C   ;compare with current escape ASCII code (0=match)
E4FD	ORA &0275   ;or with current ESCAPE status (0=ESC, 1=ASCII)
E500	BNE &E4A8   ;if ASCII or no match E4A8 to enter byte in buffer
E502	LDA &0258   ;else get ESCAPE/BREAK action byte
E505	ROR         ;Rotate to get ESCAPE bit into carry
E506	TYA         ;get character back in A
E507	BCS &E513   ;and if escape disabled exit with carry clear
E509	LDY #&06    ;else signal EVENT 6 Escape pressed
E50B	JSR &E494   ;
E50E	BCC &E513   ;if event handles ESCAPE then exit with carry clear
E510	JSR &E674   ;else set ESCAPE flag
E513	CLC         ;clear carry
E514	RTS         ;and exit


******** get a byte from keyboard buffer and interpret as necessary *****
;on entry A=cursor editing status 1=return &87-&8B,
;2= use cursor keys as soft keys 11-15
;this area not reached if cursor editing is normal

E515	ROR         ;get bit 1 into carry
E516	PLA         ;get back A
E517	BCS &E592   ;if carry is set return
    	            ;else cursor keys are 'soft'
E519	TYA         ;A=Y get back original key code (&80-&FF)
E51A	PHA         ;PUSH A
E51B	LSR         ;get high nybble into lo
E51C	LSR         ;
E51D	LSR         ;
E51E	LSR         ;A=8-&F
E51F	EOR #&04    ;and invert bit 2
    	            ;&8 becomes &C
    	            ;&9 becomes &D
    	            ;&A becomes &E
    	            ;&B becomes &F
    	            ;&C becomes &8
    	            ;&D becomes &9
    	            ;&E becomes &A
    	            ;&F becomes &B
    	
E521	TAY         ;Y=A = 8-F
E522	LDA &0265,Y ;read 026D to 0274 code interpretation status
    	            ;0=ignore key, 1=expand as 'soft' key
    	            ;2-&FF add this to base for ASCII code
    	            ;note that provision is made for keypad operation
    	            ;as codes &C0-&FF cannot be generated from keyboard
    	            ;but are recognised by OS
    	            ;
E525	CMP #&01    ;is it 01
E527	BEQ &E594   ;if so expand as 'soft' key via E594
E529	PLA         ;else get back original byte
E52A	BCC &E539   ;if above CMP generated Carry then code 0 must have
    	            ;been returned so E539 to ignore
E52C	AND #&0F    ;else add ASCII to BASE key number so clear hi nybble
E52E	CLC         ;clear carry
E52F	ADC &0265,Y ;add ASCII base
E532	CLC         ;clear carry
E533	RTS         ;and exit
    	            ;
*********** ERROR MADE IN USING EDIT FACILITY ***************************

E534	JSR &E86F   ;produce bell
E537	PLA         ;get back A, buffer number
E538	TAX         ;X=buffer number

********get byte from buffer ********************************************

E539	JSR &E460   ;get byte from buffer X
E53C	BCS &E593   ;if buffer empty E593 to exit
E53E	PHA         ;else Push byte
E53F	CPX #&01    ;and if RS423 input buffer is not the one
E541	BNE &E549   ;then E549

E543	JSR &E173   ;else oswrch
E546	LDX #&01    ;X=1 (RS423 input buffer)
E548	SEC         ;set carry

E549	PLA         ;get back original byte
E54A	BCC &E551   ;if carry clear (I.E not RS423 input) E551
E54C	LDY &0245   ;else Y=RS423 mode (0 treat as keyboard )
E54F	BNE &E592   ;if not 0 ignore escapes etc. goto E592

E551	TAY         ;Y=A
E552	BPL &E592   ;if code is less that &80 its simple so E592
E554	AND #&0F    ;else clear high nybble
E556	CMP #&0B    ;if less than 11 then treat as special code
E558	BCC &E519   ;or function key and goto E519
E55A	ADC #&7B    ;else add &7C (&7B +C) to convert codes B-F to 7-B
E55C	PHA         ;Push A
E55D	LDA &027D   ;get cursor editing status
E560	BNE &E515   ;if not 0 (normal) E515
E562	LDA &027C   ;else get character destination status

;Bit 0 enables  RS423 driver
;BIT 1 disables VDU driver
;Bit 2 disables printer driver
;BIT 3 enables  printer independent of CTRL B or CTRL C
;Bit 4 disables spooled output
;BIT 5 not used
;Bit 6 disables printer driver unless VDU 1 precedes character
;BIT 7 not used

E565	ROR         ;get bit 1 into carry
E566	ROR         ;
E567	PLA         ;
E568	BCS &E539   ;if carry is set E539 screen disabled
E56A	CMP #&87    ;else is it COPY key
E56C	BEQ &E5A6   ;if so E5A6

E56E	TAY         ;else Y=A
E56F	TXA         ;A=X
E570	PHA         ;Push X
E571	TYA         ;get back Y
E572	JSR &D8CE   ;execute edit action

E575	PLA         ;restore X
E576	TAX         ;
E577	BIT &025F   ;check econet RDCH flag
E57A	BPL &E581   ;if not set goto E581
E57C	LDA #&06    ;else Econet function 6
E57E	JMP (&0224) ;to the Econet vector


********* get byte from key string **************************************
;on entry 0268 contains key length
;and 02C9 key string pointer to next byte

E581	LDA &0268   ;get length of keystring
E584	BEQ &E539   ;if 0 E539 get a character from the buffer
E586	LDY &02C9   ;get soft key expansion pointer
E589	LDA &0B01,Y ;get character from string
E58C	INC &02C9   ;increment pointer
E58F	DEC &0268   ;decrement length


************** exit with carry clear ************************************

E592	CLC         ;
E593	RTS         ;exit
    	            ;
*** expand soft key strings *********************************************
Y=pointer to sring number

E594	PLA         ;restore original code
E595	AND #&0F    ;blank hi nybble to get key string number
E597	TAY         ;Y=A
E598	JSR &E3A8   ;get string length in A
E59B	STA &0268   ;and store it
E59E	LDA &0B00,Y ;get start point
E5A1	STA &02C9   ;and store it
E5A4	BNE &E577   ;if not 0 then get byte via E577 and exit


*********** deal with COPY key ******************************************

E5A6	TXA         ;A=X
E5A7	PHA         ;Push A
E5A8	JSR &D905   ;read a character from the screen
E5AB	TAY         ;Y=A
E5AC	BEQ &E534   ;if not valid A=0 so BEEP
E5AE	PLA         ;else restore X
E5AF	TAX         ;
E5B0	TYA         ;and Y
E5B1	CLC         ;clear carry
E5B2	RTS         ;and exit


\ No newline at end of file