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21_11_87/T\SWR05
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
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| Tape/disk: | Home » CEEFAX disks » telesoftware3.adl |
| Filename: | 21_11_87/T\SWR05 |
| Read OK: | ✔ |
| File size: | 2784 bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
Duplicates
There is 1 duplicate copy of this file in the archive:
- CEEFAX disks » telesoftware3.adl » 21_11_87/T\SWR05
- CEEFAX disks » telesoftware8.adl » 05-08-88/T\SWR05
File contents
Mastering Sideways ROM & RAM - Module 05 - Reading arguments
------------------------------------------------------------
In this module I will extend the interpreter introduced in Module 3
to include reading arguments which follow the * command.
There are two MOS subroutines used to read arguments. They are
Gsinit at &FFC2 and Gsread at &FFC5.
Gsinit should be used to initialise an argument which is to be read
using Gsread. Gsinit uses the text pointers at &F2 and &F3 with an
offset in the Y register to identify the argument address. The
argument can be enclosed by quotation marks but it does not have to
be. Gsinit is used to strip off any leading spaces and to set up an
information byte in zero page which indicates the termination
character of the argument.
Before calling Gsinit you should clear the carry flag if you want
the second quotation mark, the first space within the argument, or a
carriage return as the terminating character. You should set the carry
flag before calling Gsinit if you do not want a space to be recognised
as a terminating character. If in doubt, set the carry flag before
calling Gsinit.
After calling Gsinit the Y register contains an offset to the first
character of the argument and the accumulator contains the first
character of the argument. The zero flag is set if the argument is a
null string.
For example, imagine you have typed *CURSOR ON and the interpreter
has recognised the command CURSOR. Before calling Gsinit, the text
pointers at &F2 and &F3 will point to the command with the offset in Y
pointing to the second R of CURSOR. After calling Gsinit the offset in
Y will point to the O of ON, the zero flag will be clear, and the
terminating character will be the carriage return after the N of ON.
If ON is enclosed by quotation marks the offset in Y will still point
to the O of ON and the zero flag will be clear, but the terminating
character will be the second quotation mark. If an argument is not
typed or if *CURSOR "" is typed the zero flag will be set on return
from Gsinit. Figure 5.1 shows the offset in the Y register pointing to
the end of the command before calling Gsinit and pointing to the
beginning of the argument after calling Gsinit.
+- Y before Gsinit -+
! !
v v
>*CURSOR ON >*CURSOR "ON"
^ ^
! !
+-- Y after Gsinit --+
Figure 5.1 The offset in Y before and after calling Gsinit.
-----------------------------------------------------------
Gsread is used to read each byte of the argument. This routine
should only be used following a Gsinit call or a previous Gsread.
Following Gsinit the text pointers and Y register will point to the
first byte of the argument. After calling Gsread the accumulator
contains the character read from the argument, Y is incremented to
point to the next character, X is preserved and the carry flag is set
if the terminating character has been read.
The effect of calling Gsread is similar to, but not the same as:
LDA (&F2),Y
INY
The difference exists because Gsread tests the content of A to see
if the terminating character, and hence the end of the argument, has
been read. The terminating character can be either a second quotation
mark, a space or a carriage return as defined by Gsinit. Using Gsinit
to initialise an argument and Gsread to read it is more versatile than
simply reading the argument using post-indexed indirect addressing
with the text pointers. The difference may seem insignificant with the
simple example used above but it is useful if the argument is a number
when the place value of a particular character depends on its
displacement from the terminating character. Reading numerical
arguments will be covered in module 11.
Because the effect of using Gsread is very similar to reading a
string using post-indexed indirect addressing with the text pointers
you may be tempted to use Gsread in the interpreter to read the
unrecognised command. If you do you will find that most of the time it
will work but, sooner or later, you will start getting mysterious "bad
string" error messages. Don't be tempted into wasting your time using
Gsread in the interpreter. Stick with the method demonstrated in
Module 3.
Figure 5.2 shows how the interpreter used in the last two modules
can be modified to read an argument.
.found
SEC \ terminate with Return or "
JSR &FFC2 \ initialise argument with Gsinit
BEQ exit \ branch if null argument
JSR &FFC5 \ read first character with Gsread
BCS exit \ branch if end of argument
AND #&DF \ force upper case
.
.
.
.exit
PLA \ discard Y
PLA \ discard X
PLA \ discard A
LDA #0 \ service call recognised
RTS \ return to MOS
Figure 5.2 Using Gsinit and Gsread to read an argument.
-------------------------------------------------------
The carry flag is set before calling Gsinit. The terminating
character of the argument will be a carriage return or a second
quotation mark. After setting the carry flag Gsinit is called to
initialise the argument. If the argument is null Gsinit returns with
the zero flag set. This can be tested and branch to exit if there is
nothing to read. If the zero flag is clear there is an argument to be
read by calling Gsread for each character. Gsread will return with the
carry flag set when the terminating character is read and an
appropriate branch can be made after testing the carry flag.
This method of reading an argument has been used in the progran
CURSOR. When the interpreter (lines 280-540) recognises the command
*CURSOR it passes control to the label ".found" (line 550). The
argument is initialised (lines 560-570) and the argument is tested
(line 580). If a null argument is detected the program returns control
to the MOS with A=0 (lines 860-910). If an argument is found the
program expects to read either ON or OFF. To test for ON or OFF the
first character can be skipped since it should be an "O" (line 590).
The next character is read using Gsread (line 600) and tested for a
terminating character (line 610) and either "F" (line 630) or "N"
(line 650). There is no need to read and test for the second F of OFF.
If the second character of the argument is "F" the cursor is switched
off (lines 690-850), if it is "N" the cursor is switched on (lines
670-850).
When you load the object code generated by CURSOR into SWR to see
how it works it is possible to deceive yourself into believing that
there is something wrong with it. If you type *CURSOR OFF and press
Return the cursor will go off as expected. Type *CURSOR ON and it will
come back on. Everything seems OK. Type *CURSOR OFF and Return and
then type *CURSOR and Return. The cursor stays off because you have
not typed an argument. Everything is still OK. Now use the cursor keys
to copy the *CURSOR command without an argument and press Return. The
cursor comes back on when it should have stayed off. This will happen
because you will re-enable the cursor with the cursor keys. There is
nothing wrong with the argument reading technique demonstrated in the
program.
10 REM: CURSOR
20 MODE7
30 HIMEM=&3C00
40 DIM save 50
50 diff=&8000-HIMEM
60 comvec=&F2
70 gsinit=&FFC2
80 gsread=&FFC5
90 osasci=&FFE3
100 oscli=&FFF7
110 FOR pass = 0 TO 2 STEP 2
120 P%=HIMEM
130 [ OPT pass
140 BRK
150 BRK
160 BRK
170 JMP service+diff
180 OPT FNequb(&82)
190 OPT FNequb((copyright+diff) MOD 256)
200 BRK
210 .title
220 OPT FNequs("CURSOR")
230 .copyright
240 BRK
250 OPT FNequs("(C) Gordon Horsington 1987")
260 BRK
270 .service
280 CMP #4
290 BEQ unrecognised
300 RTS
310 .unrecognised
320 PHA
330 TXA
340 PHA
350 TYA
360 PHA
370 LDX #&FF
380 .comloop
390 INX
400 LDA title+diff,X
410 BEQ found
420 LDA (comvec),Y
430 INY
440 CMP #ASC(".")
450 BEQ found
460 AND #&DF
470 CMP title+diff,X
480 BEQ comloop
490 PLA
500 TAY
510 PLA
520 TAX
530 PLA
540 RTS
550 .found
560 SEC \ Terminate with Return or "
570 JSR gsinit
580 BEQ exit \ Branch if null argument
590 INY \ First character must be "O"
600 JSR gsread \ Second character "F" or "N"
610 BCS exit \ Branch if end of argument
620 AND #&DF \ Upper case
630 CMP #ASC("F")
640 BEQ cursoroff
650 CMP #ASC("N")
660 BNE exit
670 SEC
680 BCS cursor
690 .cursoroff
700 CLC
710 .cursor
720 PHP
730 LDA #23
740 JSR osasci
750 LDA #1
760 JSR osasci
770 PLA
780 AND #1
790 JSR osasci
800 LDA #0
810 LDX #7
820 .cursorloop
830 JSR osasci
840 DEX
850 BNE cursorloop
860 .exit
870 PLA
880 PLA
890 PLA
900 LDA #0
910 RTS
920 .lastbyte
930 ]
940 NEXT
950 INPUT'"Save filename = "filename$
960 IF filename$="" END
970 $save="SAVE "+filename$+" "+STR$~(HIMEM)+" "+STR$~(las
tbyte)+" FFFF8000 FFFF8000"
980 X%=save MOD 256
990 Y%=save DIV 256
1000 *OPT1,2
1010 CALL oscli
1020 *OPT1,0
1030 END
1040 DEFFNequb(byte)
1050 ?P%=byte
1060 P%=P%+1
1070 =pass
1080 DEFFNequw(word)
1090 ?P%=word MOD 256
1100 P%?1=word DIV 256
1110 P%=P%+2
1120 =pass
1130 DEFFNequd(double)
1140 !P%=double
1150 P%=P%+4
1160 =pass
1170 DEFFNequs(string$)
1180 $P%=string$
1190 P%=P%+LEN(string$)
1200 =pass
00000000 4d 61 73 74 65 72 69 6e 67 20 53 69 64 65 77 61 |Mastering Sidewa|
00000010 79 73 20 52 4f 4d 20 26 20 52 41 4d 20 2d 20 4d |ys ROM & RAM - M|
00000020 6f 64 75 6c 65 20 30 35 20 2d 20 52 65 61 64 69 |odule 05 - Readi|
00000030 6e 67 20 61 72 67 75 6d 65 6e 74 73 0d 2d 2d 2d |ng arguments.---|
00000040 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
00000070 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d 0d 20 20 49 6e 20 |---------.. In |
00000080 74 68 69 73 20 6d 6f 64 75 6c 65 20 49 20 77 69 |this module I wi|
00000090 6c 6c 20 65 78 74 65 6e 64 20 74 68 65 20 69 6e |ll extend the in|
000000a0 74 65 72 70 72 65 74 65 72 20 69 6e 74 72 6f 64 |terpreter introd|
000000b0 75 63 65 64 20 69 6e 20 4d 6f 64 75 6c 65 20 33 |uced in Module 3|
000000c0 0d 74 6f 20 69 6e 63 6c 75 64 65 20 72 65 61 64 |.to include read|
000000d0 69 6e 67 20 61 72 67 75 6d 65 6e 74 73 20 77 68 |ing arguments wh|
000000e0 69 63 68 20 66 6f 6c 6c 6f 77 20 74 68 65 20 2a |ich follow the *|
000000f0 20 63 6f 6d 6d 61 6e 64 2e 0d 0d 20 20 54 68 65 | command... The|
00000100 72 65 20 61 72 65 20 74 77 6f 20 4d 4f 53 20 73 |re are two MOS s|
00000110 75 62 72 6f 75 74 69 6e 65 73 20 75 73 65 64 20 |ubroutines used |
00000120 74 6f 20 72 65 61 64 20 61 72 67 75 6d 65 6e 74 |to read argument|
00000130 73 2e 20 54 68 65 79 20 61 72 65 0d 47 73 69 6e |s. They are.Gsin|
00000140 69 74 20 61 74 20 26 46 46 43 32 20 61 6e 64 20 |it at &FFC2 and |
00000150 47 73 72 65 61 64 20 61 74 20 26 46 46 43 35 2e |Gsread at &FFC5.|
00000160 0d 0d 20 20 47 73 69 6e 69 74 20 73 68 6f 75 6c |.. Gsinit shoul|
00000170 64 20 62 65 20 75 73 65 64 20 74 6f 20 69 6e 69 |d be used to ini|
00000180 74 69 61 6c 69 73 65 20 61 6e 20 61 72 67 75 6d |tialise an argum|
00000190 65 6e 74 20 77 68 69 63 68 20 69 73 20 74 6f 20 |ent which is to |
000001a0 62 65 20 72 65 61 64 0d 75 73 69 6e 67 20 47 73 |be read.using Gs|
000001b0 72 65 61 64 2e 20 47 73 69 6e 69 74 20 75 73 65 |read. Gsinit use|
000001c0 73 20 74 68 65 20 74 65 78 74 20 70 6f 69 6e 74 |s the text point|
000001d0 65 72 73 20 61 74 20 26 46 32 20 61 6e 64 20 26 |ers at &F2 and &|
000001e0 46 33 20 77 69 74 68 20 61 6e 0d 6f 66 66 73 65 |F3 with an.offse|
000001f0 74 20 69 6e 20 74 68 65 20 59 20 72 65 67 69 73 |t in the Y regis|
00000200 74 65 72 20 74 6f 20 69 64 65 6e 74 69 66 79 20 |ter to identify |
00000210 74 68 65 20 61 72 67 75 6d 65 6e 74 20 61 64 64 |the argument add|
00000220 72 65 73 73 2e 20 54 68 65 0d 61 72 67 75 6d 65 |ress. The.argume|
00000230 6e 74 20 63 61 6e 20 62 65 20 65 6e 63 6c 6f 73 |nt can be enclos|
00000240 65 64 20 62 79 20 71 75 6f 74 61 74 69 6f 6e 20 |ed by quotation |
00000250 6d 61 72 6b 73 20 62 75 74 20 69 74 20 64 6f 65 |marks but it doe|
00000260 73 20 6e 6f 74 20 68 61 76 65 20 74 6f 0d 62 65 |s not have to.be|
00000270 2e 20 47 73 69 6e 69 74 20 69 73 20 75 73 65 64 |. Gsinit is used|
00000280 20 74 6f 20 73 74 72 69 70 20 6f 66 66 20 61 6e | to strip off an|
00000290 79 20 6c 65 61 64 69 6e 67 20 73 70 61 63 65 73 |y leading spaces|
000002a0 20 61 6e 64 20 74 6f 20 73 65 74 20 75 70 20 61 | and to set up a|
000002b0 6e 0d 69 6e 66 6f 72 6d 61 74 69 6f 6e 20 62 79 |n.information by|
000002c0 74 65 20 69 6e 20 7a 65 72 6f 20 70 61 67 65 20 |te in zero page |
000002d0 77 68 69 63 68 20 69 6e 64 69 63 61 74 65 73 20 |which indicates |
000002e0 74 68 65 20 74 65 72 6d 69 6e 61 74 69 6f 6e 0d |the termination.|
000002f0 63 68 61 72 61 63 74 65 72 20 6f 66 20 74 68 65 |character of the|
00000300 20 61 72 67 75 6d 65 6e 74 2e 0d 0d 20 20 42 65 | argument... Be|
00000310 66 6f 72 65 20 63 61 6c 6c 69 6e 67 20 47 73 69 |fore calling Gsi|
00000320 6e 69 74 20 79 6f 75 20 73 68 6f 75 6c 64 20 63 |nit you should c|
00000330 6c 65 61 72 20 74 68 65 20 63 61 72 72 79 20 66 |lear the carry f|
00000340 6c 61 67 20 69 66 20 79 6f 75 20 77 61 6e 74 0d |lag if you want.|
00000350 74 68 65 20 73 65 63 6f 6e 64 20 71 75 6f 74 61 |the second quota|
00000360 74 69 6f 6e 20 6d 61 72 6b 2c 20 74 68 65 20 66 |tion mark, the f|
00000370 69 72 73 74 20 73 70 61 63 65 20 77 69 74 68 69 |irst space withi|
00000380 6e 20 74 68 65 20 61 72 67 75 6d 65 6e 74 2c 20 |n the argument, |
00000390 6f 72 20 61 0d 63 61 72 72 69 61 67 65 20 72 65 |or a.carriage re|
000003a0 74 75 72 6e 20 61 73 20 74 68 65 20 74 65 72 6d |turn as the term|
000003b0 69 6e 61 74 69 6e 67 20 63 68 61 72 61 63 74 65 |inating characte|
000003c0 72 2e 20 59 6f 75 20 73 68 6f 75 6c 64 20 73 65 |r. You should se|
000003d0 74 20 74 68 65 20 63 61 72 72 79 0d 66 6c 61 67 |t the carry.flag|
000003e0 20 62 65 66 6f 72 65 20 63 61 6c 6c 69 6e 67 20 | before calling |
000003f0 47 73 69 6e 69 74 20 69 66 20 79 6f 75 20 64 6f |Gsinit if you do|
00000400 20 6e 6f 74 20 77 61 6e 74 20 61 20 73 70 61 63 | not want a spac|
00000410 65 20 74 6f 20 62 65 20 72 65 63 6f 67 6e 69 73 |e to be recognis|
00000420 65 64 0d 61 73 20 61 20 74 65 72 6d 69 6e 61 74 |ed.as a terminat|
00000430 69 6e 67 20 63 68 61 72 61 63 74 65 72 2e 20 49 |ing character. I|
00000440 66 20 69 6e 20 64 6f 75 62 74 2c 20 73 65 74 20 |f in doubt, set |
00000450 74 68 65 20 63 61 72 72 79 20 66 6c 61 67 20 62 |the carry flag b|
00000460 65 66 6f 72 65 0d 63 61 6c 6c 69 6e 67 20 47 73 |efore.calling Gs|
00000470 69 6e 69 74 2e 0d 0d 20 20 41 66 74 65 72 20 63 |init... After c|
00000480 61 6c 6c 69 6e 67 20 47 73 69 6e 69 74 20 74 68 |alling Gsinit th|
00000490 65 20 59 20 72 65 67 69 73 74 65 72 20 63 6f 6e |e Y register con|
000004a0 74 61 69 6e 73 20 61 6e 20 6f 66 66 73 65 74 20 |tains an offset |
000004b0 74 6f 20 74 68 65 20 66 69 72 73 74 0d 63 68 61 |to the first.cha|
000004c0 72 61 63 74 65 72 20 6f 66 20 74 68 65 20 61 72 |racter of the ar|
000004d0 67 75 6d 65 6e 74 20 61 6e 64 20 74 68 65 20 61 |gument and the a|
000004e0 63 63 75 6d 75 6c 61 74 6f 72 20 63 6f 6e 74 61 |ccumulator conta|
000004f0 69 6e 73 20 74 68 65 20 66 69 72 73 74 0d 63 68 |ins the first.ch|
00000500 61 72 61 63 74 65 72 20 6f 66 20 74 68 65 20 61 |aracter of the a|
00000510 72 67 75 6d 65 6e 74 2e 20 54 68 65 20 7a 65 72 |rgument. The zer|
00000520 6f 20 66 6c 61 67 20 69 73 20 73 65 74 20 69 66 |o flag is set if|
00000530 20 74 68 65 20 61 72 67 75 6d 65 6e 74 20 69 73 | the argument is|
00000540 20 61 0d 6e 75 6c 6c 20 73 74 72 69 6e 67 2e 0d | a.null string..|
00000550 0d 20 20 46 6f 72 20 65 78 61 6d 70 6c 65 2c 20 |. For example, |
00000560 69 6d 61 67 69 6e 65 20 79 6f 75 20 68 61 76 65 |imagine you have|
00000570 20 74 79 70 65 64 20 2a 43 55 52 53 4f 52 20 4f | typed *CURSOR O|
00000580 4e 20 61 6e 64 20 74 68 65 20 69 6e 74 65 72 70 |N and the interp|
00000590 72 65 74 65 72 0d 68 61 73 20 72 65 63 6f 67 6e |reter.has recogn|
000005a0 69 73 65 64 20 74 68 65 20 63 6f 6d 6d 61 6e 64 |ised the command|
000005b0 20 43 55 52 53 4f 52 2e 20 42 65 66 6f 72 65 20 | CURSOR. Before |
000005c0 63 61 6c 6c 69 6e 67 20 47 73 69 6e 69 74 2c 20 |calling Gsinit, |
000005d0 74 68 65 20 74 65 78 74 0d 70 6f 69 6e 74 65 72 |the text.pointer|
000005e0 73 20 61 74 20 26 46 32 20 61 6e 64 20 26 46 33 |s at &F2 and &F3|
000005f0 20 77 69 6c 6c 20 70 6f 69 6e 74 20 74 6f 20 74 | will point to t|
00000600 68 65 20 63 6f 6d 6d 61 6e 64 20 77 69 74 68 20 |he command with |
00000610 74 68 65 20 6f 66 66 73 65 74 20 69 6e 20 59 0d |the offset in Y.|
00000620 70 6f 69 6e 74 69 6e 67 20 74 6f 20 74 68 65 20 |pointing to the |
00000630 73 65 63 6f 6e 64 20 52 20 6f 66 20 43 55 52 53 |second R of CURS|
00000640 4f 52 2e 20 41 66 74 65 72 20 63 61 6c 6c 69 6e |OR. After callin|
00000650 67 20 47 73 69 6e 69 74 20 74 68 65 20 6f 66 66 |g Gsinit the off|
00000660 73 65 74 20 69 6e 0d 59 20 77 69 6c 6c 20 70 6f |set in.Y will po|
00000670 69 6e 74 20 74 6f 20 74 68 65 20 4f 20 6f 66 20 |int to the O of |
00000680 4f 4e 2c 20 74 68 65 20 7a 65 72 6f 20 66 6c 61 |ON, the zero fla|
00000690 67 20 77 69 6c 6c 20 62 65 20 63 6c 65 61 72 2c |g will be clear,|
000006a0 20 61 6e 64 20 74 68 65 0d 74 65 72 6d 69 6e 61 | and the.termina|
000006b0 74 69 6e 67 20 63 68 61 72 61 63 74 65 72 20 77 |ting character w|
000006c0 69 6c 6c 20 62 65 20 74 68 65 20 63 61 72 72 69 |ill be the carri|
000006d0 61 67 65 20 72 65 74 75 72 6e 20 61 66 74 65 72 |age return after|
000006e0 20 74 68 65 20 4e 20 6f 66 20 4f 4e 2e 0d 49 66 | the N of ON..If|
000006f0 20 4f 4e 20 69 73 20 65 6e 63 6c 6f 73 65 64 20 | ON is enclosed |
00000700 62 79 20 71 75 6f 74 61 74 69 6f 6e 20 6d 61 72 |by quotation mar|
00000710 6b 73 20 74 68 65 20 6f 66 66 73 65 74 20 69 6e |ks the offset in|
00000720 20 59 20 77 69 6c 6c 20 73 74 69 6c 6c 20 70 6f | Y will still po|
00000730 69 6e 74 0d 74 6f 20 74 68 65 20 4f 20 6f 66 20 |int.to the O of |
00000740 4f 4e 20 61 6e 64 20 74 68 65 20 7a 65 72 6f 20 |ON and the zero |
00000750 66 6c 61 67 20 77 69 6c 6c 20 62 65 20 63 6c 65 |flag will be cle|
00000760 61 72 2c 20 62 75 74 20 74 68 65 20 74 65 72 6d |ar, but the term|
00000770 69 6e 61 74 69 6e 67 0d 63 68 61 72 61 63 74 65 |inating.characte|
00000780 72 20 77 69 6c 6c 20 62 65 20 74 68 65 20 73 65 |r will be the se|
00000790 63 6f 6e 64 20 71 75 6f 74 61 74 69 6f 6e 20 6d |cond quotation m|
000007a0 61 72 6b 2e 20 49 66 20 61 6e 20 61 72 67 75 6d |ark. If an argum|
000007b0 65 6e 74 20 69 73 20 6e 6f 74 0d 74 79 70 65 64 |ent is not.typed|
000007c0 20 6f 72 20 69 66 20 2a 43 55 52 53 4f 52 20 22 | or if *CURSOR "|
000007d0 22 20 69 73 20 74 79 70 65 64 20 74 68 65 20 7a |" is typed the z|
000007e0 65 72 6f 20 66 6c 61 67 20 77 69 6c 6c 20 62 65 |ero flag will be|
000007f0 20 73 65 74 20 6f 6e 20 72 65 74 75 72 6e 0d 66 | set on return.f|
00000800 72 6f 6d 20 47 73 69 6e 69 74 2e 20 46 69 67 75 |rom Gsinit. Figu|
00000810 72 65 20 35 2e 31 20 73 68 6f 77 73 20 74 68 65 |re 5.1 shows the|
00000820 20 6f 66 66 73 65 74 20 69 6e 20 74 68 65 20 59 | offset in the Y|
00000830 20 72 65 67 69 73 74 65 72 20 70 6f 69 6e 74 69 | register pointi|
00000840 6e 67 20 74 6f 0d 74 68 65 20 65 6e 64 20 6f 66 |ng to.the end of|
00000850 20 74 68 65 20 63 6f 6d 6d 61 6e 64 20 62 65 66 | the command bef|
00000860 6f 72 65 20 63 61 6c 6c 69 6e 67 20 47 73 69 6e |ore calling Gsin|
00000870 69 74 20 61 6e 64 20 70 6f 69 6e 74 69 6e 67 20 |it and pointing |
00000880 74 6f 20 74 68 65 0d 62 65 67 69 6e 6e 69 6e 67 |to the.beginning|
00000890 20 6f 66 20 74 68 65 20 61 72 67 75 6d 65 6e 74 | of the argument|
000008a0 20 61 66 74 65 72 20 63 61 6c 6c 69 6e 67 20 47 | after calling G|
000008b0 73 69 6e 69 74 2e 0d 0d 0d 0d 0d 20 20 20 20 20 |sinit...... |
000008c0 20 20 2b 2d 20 59 20 62 65 66 6f 72 65 20 47 73 | +- Y before Gs|
000008d0 69 6e 69 74 20 2d 2b 0d 20 20 20 20 20 20 20 21 |init -+. !|
000008e0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000008f0 20 20 20 21 0d 20 20 20 20 20 20 20 76 20 20 20 | !. v |
00000900 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00000910 76 0d 3e 2a 43 55 52 53 4f 52 20 4f 4e 20 20 20 |v.>*CURSOR ON |
00000920 20 20 20 20 20 20 3e 2a 43 55 52 53 4f 52 20 22 | >*CURSOR "|
00000930 4f 4e 22 0d 20 20 20 20 20 20 20 20 20 5e 20 20 |ON". ^ |
00000940 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00000950 20 20 5e 0d 20 20 20 20 20 20 20 20 20 21 20 20 | ^. ! |
00000960 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00000970 20 20 21 0d 20 20 20 20 20 20 20 20 20 2b 2d 2d | !. +--|
00000980 20 59 20 61 66 74 65 72 20 47 73 69 6e 69 74 20 | Y after Gsinit |
00000990 2d 2d 2b 0d 0d 46 69 67 75 72 65 20 35 2e 31 20 |--+..Figure 5.1 |
000009a0 54 68 65 20 6f 66 66 73 65 74 20 69 6e 20 59 20 |The offset in Y |
000009b0 62 65 66 6f 72 65 20 61 6e 64 20 61 66 74 65 72 |before and after|
000009c0 20 63 61 6c 6c 69 6e 67 20 47 73 69 6e 69 74 2e | calling Gsinit.|
000009d0 0d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |.---------------|
000009e0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
00000a00 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d 0d 0d 0d |------------....|
00000a10 0d 20 20 47 73 72 65 61 64 20 69 73 20 75 73 65 |. Gsread is use|
00000a20 64 20 74 6f 20 72 65 61 64 20 65 61 63 68 20 62 |d to read each b|
00000a30 79 74 65 20 6f 66 20 74 68 65 20 61 72 67 75 6d |yte of the argum|
00000a40 65 6e 74 2e 20 54 68 69 73 20 72 6f 75 74 69 6e |ent. This routin|
00000a50 65 0d 73 68 6f 75 6c 64 20 6f 6e 6c 79 20 62 65 |e.should only be|
00000a60 20 75 73 65 64 20 66 6f 6c 6c 6f 77 69 6e 67 20 | used following |
00000a70 61 20 47 73 69 6e 69 74 20 63 61 6c 6c 20 6f 72 |a Gsinit call or|
00000a80 20 61 20 70 72 65 76 69 6f 75 73 20 47 73 72 65 | a previous Gsre|
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