start tok64 d64-FSDj0j
0 REM"{delete*7} ponzo*83*waterloo
1 REM"{delete*6}
10 POKE53281,15:POKE53280,12:PRINT"{black}"
11 PRINT"{clear}{space*14}{reverse on}{blue}c64 tutor-5
12 PRINT"{red}{cm a}{sh asterisk*37}{cm s}"
13 PRINT"{sh -} {reverse on}{blue}the adc's of 6510 machine language {red}{reverse off} {sh -}":ms$=" welcome! "
14 PRINT"{red}{cm z}{sh asterisk*37}{cm x}{black}"
30 GOSUB60000:GOSUB63100:GOSUB63000
31 PRINT"{clear}{down*2}the {reverse on}m{reverse off}icro{reverse on}p{reverse off}rocessor {reverse on}u{reverse off}nit (mpu)"
32 PRINT"{down}in the c64 is the {reverse on}6510{reverse off}."
33 PRINT"{down}he (she?) will obey your commands"
34 PRINT"{down}if you can speak the right language"
35 PRINT"{down}{.*3}and that's{space*2}{reverse on}machine language{reverse off}."
36 PRINT"{down}we'll learn some {reverse on}machine language"
37 PRINT"{down}in this tutorial."
38 PRINT"{down}but let's let the {reverse on}6510{reverse off} tell it{.*3}"
39 GOSUB63000
40 PRINT"{clear}{cm +*12}{reverse on}the 6510{reverse off}{cm +*14}"
45 PRINT"{down}Qwe've got a number of internal"
50 PRINT"{down}'registers' which hold 8-bit binary"
60 PRINT"{down}numbers(bytes) from $00 to $ff (in hex)."
65 PRINT"{down}Qwe call them 'a' and 'x' and 'y'."
66 PRINT"{down}(we have a few more..but wait..)"
70 PRINT"{down}Qyou may load them with numbers"
80 PRINT"{down}and perform addition,subtraction,"
90 PRINT"{down}tests for zero , > , < etc.etc."
100 PRINT"{down}Qlet's go through some of these {reverse on}6510{reverse off}"
110 PRINT"{down}commands{.*3}":GOSUB63000
120 PRINT"{clear}"a$x$y$
130 PRINTsd$"here are a few of the commands"
140 PRINT"{down}in my repertoire:"
150 GOSUB63200
160 PRINT"{reverse on}lda #$f3"
170 PRINT"{down}{reverse on}l{reverse off}oa{reverse on}d{reverse off} the {reverse on}a{reverse off}ccumulator with{space*2}the"
180 PRINT"{down}number f3 in hex..#$f3"
190 PRINT"{down}this is an {reverse on}immediate{reverse off} load."
200 ms$="{space*2}a=#$f3{space*2}":GOSUB63300:n$="{1*4}0011":GOSUB40110:GOSUB63200
210 PRINT"{reverse on}ldx #$ab":ms$="{space*2}x=#$ab{space*2}":GOSUB63300
215 n$="10101011":GOSUB40130:GOSUB63200
220 PRINT"{reverse on}ldy #$dd":ms$="{space*2}y=#$dd{space*2}":GOSUB63300:n$="110{1*3}01":GOSUB40140
230 GOSUB63200:PRINT"{reverse on}tax":PRINT"{down}{reverse on}t{reverse off}ransfer contents of {reverse on}a{reverse off} to {reverse on}x{reverse off}."
235 ms$="{space*3}x=a{space*4}":GOSUB63300:GOSUB41130:GOSUB63200
240 PRINT"{reverse on}tya":PRINT"{down}{reverse on}t{reverse off}ransfer contents of {reverse on}y{reverse off} to {reverse on}a{reverse off}.":ms$="{space*3}a=y{space*3}"
245 GOSUB63300:GOSUB41410:GOSUB63200
250 PRINT"..and there's {reverse on}txa{reverse off} and {reverse on}tay{reverse off}."
270 PRINT"{down*2}{reverse on}here are some more{reverse off}:":GOSUB63200
280 PRINT"{reverse on}inx{reverse off}":PRINT"{down}{reverse on}in{reverse off}crement the {reverse on}x{reverse off}-register by 1.":ms$="{space*2}x=x+1{space*3}"
290 GOSUB63300:n$="10101100":GOSUB40130:GOSUB63200
300 PRINT"{reverse on}dex{reverse off}":PRINT"{down}{reverse on}de{reverse off}crement the {reverse on}x{reverse off}-register by 1.":ms$="{space*2}x=x-1{space*2}"
310 GOSUB63300:n$="10101011":GOSUB40130:GOSUB63200
320 PRINT"and there's {reverse on}iny{reverse off} and {reverse on}dey{reverse off}.":GOSUB63200
330 PRINTm$:n$="10110101":pp=0:GOSUB40160:PRINTml$"$1234":pp=20
340 PRINTsd$"{reverse on}inc $1234{reverse off}":PRINT"{down}{reverse on}inc{reverse off}rements memory location $1234"
350 ms$="{space*2}m=m+1{space*2}":GOSUB63300:n$="10110110":GOSUB40160:GOSUB63200
360 PRINT"{reverse on}dec $1234{reverse off}":PRINT"{down}{reverse on}dec{reverse off}rements memory location $1234"
370 ms$="{space*3}m=m-1{space*2}":GOSUB63300:n$="10110101":GOSUB40160:GOSUB63200
380 PRINT"{reverse on}asl{reverse off}":PRINT"{down}{reverse on}a{reverse off}rithmetic {reverse on}s{reverse off}hift {reverse on}l{reverse off}eft"
390 PRINT"{down}all bits of the {reverse on}a{reverse off}-register move left."
400 PRINT"{down}a '0' comes into the 'lsb' and"
410 PRINT"{down}the 'msb' drops into the 'carry'."
420 PRINT"{down}Qlsb=least significant bit"
430 PRINT"{down}Qmsb=most significant bit"
435 ms$="{space*2}a=2*a{space*3}":GOSUB63300
440 PRINTc$:POKEc,49:n$="10{1*3}010":pp=500:GOSUB40098:GOSUB63200:pp=20
450 PRINTcc$:POKEc,32
460 PRINTsd$"{down}{reverse on}sec{reverse off}":PRINT"{down}{reverse on}se{reverse off}t the {reverse on}c{reverse off}arry bit."
470 PRINTcr$:ms$="{space*2}carry=1 ":GOSUB63300:POKEc,49:GOSUB63200
480 PRINTsd$"{down}{reverse on}clc{reverse off}":PRINT"{down}{reverse on}cl{reverse off}ear {reverse on}c{reverse off}arry bit.":ms$="{space*2}carry=0 "
490 GOSUB63300:PRINTcr$:POKEc,48:GOSUB63200:PRINTcc$
500 PRINT"{reverse on}sta $1234{reverse off}":PRINT"{down}{reverse on}st{reverse off}ore the {reverse on}a{reverse off}-register"
510 PRINT"{down}in memory location $1234":ms$="{space*3}m=a{space*4}":GOSUB63300
520 n$="10{1*3}010":GOSUB41160:GOSUB63000
600 PRINT"{clear}that's enough. let's clear the screen.{down}"
610 PRINT"lda #$20{space*2}{arrow left}load a with #$20='space'."
620 PRINT"sta $0400 I":PRINT"sta $0401 {sh -}{arrow left}fills screen"
630 PRINT"sta $0402 {sh -}{arrow left}memory with #$20."
640 PRINT"{-*3} {-*5} .{-*16}":PRINT"sta $07ff K{arrow left}hence clear screen"
650 PRINT"{down}but we clearly need something like:":PRINT"{down}lda #$20"
660 PRINT"for x=0 to #$3ff":PRINT"sta $0400+x":PRINT"next x":GOSUB63000
670 PRINT"{clear}or{down}{left*2}{cm u*2}":PRINT"begin lda #$20 {arrow left}note statement label"
680 PRINT"{space*6}ldx #$00":PRINT"loop{space*2}sta $0400,x {arrow left}{reverse on}indexed addressing"
690 PRINT"{space*3}^{space*2}inx":PRINT"{space*3}{sh -}{space*2}?check for x=#$3ff?"
695 PRINT"{space*3}{cm z}{sh asterisk} if not,goto 'loop'"
700 PRINT"{down*2}we have {reverse on}compare{reverse off} & {reverse on}branch{reverse off} instructions!"
710 PRINT"{down}what we need above is:":PRINT"{down}{reverse on}c{reverse off}om{reverse on}p{reverse off}are {reverse on}x{reverse off} to #$3ff"
720 PRINT"{down}& {reverse on}b{reverse off}ranch if {reverse on}n{reverse off}ot {reverse on}e{reverse off}qual..to 'loop'":GOSUB63010
730 PRINT"{home}{down*2}{reverse on}begin lda #$20{space*3}{reverse off}{space*19}"
740 PRINT"{reverse on}{space*6}ldx #$00{space*3}":PRINT"{reverse on}loop{space*2}sta $0400,x"
750 PRINT"{reverse on}{space*3}^{space*2}inx{space*8}":PRINT"{reverse on}{space*3}{sh -}{space*2}cpx #$3ff{space*2}{reverse off}{space*22}"
760 PRINT"{reverse on}{space*3}{cm z}{sh asterisk} bne loop{space*3}{reverse off}{space*15}":GOSUB63200
770 PRINT"note{down}{left*4}{cm u*4}{up}:we will never {reverse on}sta{reverse off} in {reverse on}$07ff{reverse off}"
780 PRINT"{down}in the above program{.*3}so{.*3}":GOSUB63010
790 PRINT"{home}{down*6}{reverse on}{space*3}{sh -}{space*2}cpx #$400{space*2}":GOSUB63200
800 PRINT"also, we can {reverse on}cpx #$n{reverse off} only if n lies"
810 PRINT"{down}in the range $00 to $ff."
820 PRINT"{down}so we change the code to:":GOSUB63010
830 PRINT"{clear}{down*2}{reverse on}begin lda #$20{space*3}{reverse off}"
840 PRINT"{reverse on}{space*6}ldx #$00{space*3}":PRINT"{reverse on}loop{space*2}sta $0400,x"
850 PRINT"{reverse on}{space*6}sta $0500,x"
860 PRINT"{reverse on}{space*6}sta $0600,x"
870 PRINT"{reverse on}{space*6}sta $0700,x"
880 PRINT"{reverse on}{space*6}inx{space*8}":PRINT"{reverse on}{space*6}cpx #$ff{space*3}{reverse off}"
890 PRINT"{reverse on}{space*6}bne loop{space*3}{reverse off}":GOSUB63000
900 PRINTsd$"{down*4}";:FORt=1TO10:PRINTcl$:NEXT:PRINTsd$"{down*4}";
910 PRINT"or, we can simplify this a little by"
920 PRINT"{down}counting {reverse on}down{reverse off} from x=$ff to $00":GOSUB63010
930 PRINT"{home}{down*2}{reverse on}begin lda #$20{space*3}{reverse off}"
940 PRINT"{reverse on}{space*6}ldx #$ff{space*3}":PRINT"{reverse on}loop{space*2}sta $0400,x"
950 PRINT"{reverse on}{space*6}sta $0500,x"
960 PRINT"{reverse on}{space*6}sta $0600,x"
970 PRINT"{reverse on}{space*6}sta $0700,x"
980 PRINT"{reverse on}{space*6}dex{space*8}"
990 PRINT"{reverse on}{space*6}bne loop{space*3}{reverse off}":PRINT"{space*19}":GOSUB63000
991 PRINTsd$"{down*4}";:FORt=1TO10:PRINTcl$:NEXT:PRINTsd$"{down*4}";
995 PRINT"{down*3}how can we {reverse on}bne{reverse off} when we don't do any"
996 PRINT"{down}{reverse on}compare{reverse off}?":GOSUB63000
1000 PRINT"{clear}you see, {reverse on}bne{reverse off} really checks to see"
1010 PRINT"{down}if '0' is the result of an arithmetic"
1020 PRINT"{down}operation..including a {reverse on}compare{reverse off}."
1030 PRINT"{down}in the pair of instructions:"
1040 PRINT"{down}{reverse on}cpx #$ff":PRINT"{reverse on}bne loop":PRINT"{down}we subtract #$ff from the"
1050 PRINT"{down}value of x and {reverse on}branch{reverse off} to loop if"
1060 PRINT"{down}the result is not zero!":GOSUB63000
1070 PRINT"{clear}{reverse on}inx{space*5}":PRINT"{reverse on}bne loop"
1080 PRINT"{down}we branch to loop if the result of"
1090 PRINT"{down}incrementing x is {reverse on}not{reverse off} zero.":PRINT"{cm u*3}"
1100 PRINT"{down}{reverse on}dec $1234":PRINT"{reverse on}bne loop "
1110 PRINT"{down}here we branch to loop if"
1120 PRINT"{down}decrementing $1234 is not zero.":PRINT"{cm u*3}"
1130 PRINT"{down}{reverse on}note{reverse off}: {reverse on}cpx{reverse off}{space*2}involves a subtraction"
1140 PRINT"{down}(to check for zero result)"
1150 PRINT"{down}but it does not{down}{left*3}{cm u*3}{up} change any registers!":GOSUB63000
1160 PRINT"{clear}let's {reverse on}rvs{reverse off} the screen."
1170 PRINT"{down}this requires looking at every screen"
1180 PRINT"{down}memory location and checking the {reverse on}msb{reverse off}."
1190 PRINT"{down}if it's {reverse on}1{reverse off} then change it to {reverse on}0{reverse off}."
1200 PRINT"{down}if it's {reverse on}0{reverse off} then change it to {reverse on}1{reverse off}."
1300 PRINT"{down}(the msb determines if the character"
1310 PRINT"is in rvs-field)!"
1320 PRINT"{down}we'll:":PRINT"{down}{reverse on}lda $0400,x":PRINT"{reverse on}eor #$80{space*3}{reverse off} {arrow left*2}{?*3}":PRINT"{reverse on}sta $0400,x"
1330 PRINT"{down}{reverse on}eor{reverse off} is an {reverse on}e{reverse off}xclusive {reverse on}or{reverse off}!":GOSUB63000
1340 PRINT"{clear}if {reverse on}a{reverse off} contains {reverse on}10110101{reverse off} (after {reverse on}lda{reverse off})"
1350 PRINT"{down}then {reverse on}eor #$80{reverse off} does an exclusive-or"
1360 PRINT"{down}with {reverse on}1{0*7}{reverse off} ($80 in hex)"
1370 PRINT"{down}and gives {reverse on}00110101{reverse off}..very nice!"
1380 PRINT"{down}our program might go:"
1390 PRINT"{down}{reverse on}begin ldx #$ff{space*3}":PRINT"{reverse on}loop{space*2}lda $0400,x"
1400 PRINT"{reverse on}{space*6}eor #$80{space*3}":PRINT"{reverse on}{space*6}sta $0400,x"
1410 PRINT"{reverse on}{space*6}lda $0500,x":PRINT"{reverse on}{space*6}eor #$80{space*3}"
1420 PRINT"{reverse on}{space*6}sta $0500,x":PRINT"{reverse on}etc. etc..until..{reverse off}"
1430 PRINT"{reverse on}{space*6}sta $0700,x"
1440 PRINT"{reverse on}{space*6}dex{space*8}":PRINT"{reverse on}{space*6}bne loop{space*3}":GOSUB63000
1450 PRINT"{clear}it's clear that this will not do if"
1460 PRINT"{down}we want to go from $0400 to $0500 to"
1470 PRINT"{down}..to $0n00,instead of just to $0700."
1480 PRINT"{down}we need a loop-within-a-loop"
1490 PRINT"{down}for large n{.*3}something like:{down*3}"
1500 PRINT"{down}{space*5}m=$0400":PRINT"{space*5}x=n{space*5}{arrow left}{reverse on}n instead of 3"
1510 PRINT"lp1{space*2}y=#$ff":PRINT"lp2{space*2}lda m+y":PRINT"{space*5}eor #$80"
1511 PRINT"{space*5}sta m+y":PRINT"{space*5}y=y-1"
1512 PRINT"{space*5}if y<>0 goto lp2 ":PRINT"{space*5}m=m+$100":PRINT"{space*5}x=x-1"
1513 PRINT"{space*5}ifx<>0 goto lp1 ":GOSUB63000
1514 PRINT"{home}{down*20}"TAB(23)"{arrow left}{reverse on}won't do y=0{reverse off}!"
1515 PRINT"{down*2}"TAB(23)"{arrow left}{reverse on}won't do x=0{reverse off}!!{home}":GOSUB63000
1516 PRINT"{home}";:FORi=1TO10:PRINTcl$:NEXT:PRINT"{home}we'll {reverse on}change{reverse off} it to:"
1517 GOSUB63010:PRINT"{home}{down}{space*5}m=$0400":PRINT"{space*5}x=n"                    "
1518 PRINT"{reverse on}lp1{space*2}y=#$00{space*10}":PRINT"lp2{space*2}lda m+y":PRINT"{space*5}eor #$80"
1519 PRINT"{space*5}sta m+y":PRINT"{space*5}y=y-1"
1520 PRINT"{space*5}if y<>0 goto lp2 ":PRINT"{space*5}m=m+$100":PRINT"{space*5}x=x-1"
1521 PRINT"{reverse on}{space*5}ifx>=0 goto lp1 {reverse off}":GOSUB63000:PRINT"{home}{down*12}";
1522 PRINT"we work on m+00 first,then {reverse on}y=y-1{reverse off}"
1523 PRINT"will change y=00 to y=ff(!) and we'll"
1524 PRINT"continue with m+ff then m+fe..to m+01"
1525 PRINT"and we stop the y-loop there!"
1526 PRINT"the x-loop starts with x=n and each"
1527 PRINT"{reverse on}x=x-1{reverse off} changes x to n-1,n-2,..2,1,0 {reverse on}then{reverse off}"
1528 PRINT"one more {reverse on}x=x-1{reverse off} changes x to ff(!) which"
1529 PRINT"is {reverse on}negative{reverse off}(!) and we stop the x-loop!"
1530 PRINT"{reverse on}note{reverse off}:the 6510 registers can hold{space*2}#'s"
1531 PRINT"from $00 to $ff.if we have {reverse on}00{reverse off} and"
1532 PRINT"{reverse on}decrement{reverse off},it changes to {reverse on}ff{reverse off}..and {reverse on}ff+1{reverse off}={reverse on}00{reverse off}"
1533 PRINT"finally,{reverse on}msb=1{reverse off} signifies a {reverse on}negative no.{reverse off}!";:GOSUB63000
1540 PRINT"{clear}let's try something like:"
1550 PRINT"{down}{reverse on}begin lda #$0400 {reverse off}{arrow left}??*!#$0400 too big!!"
1555 PRINT"{reverse on}{space*6}sta $b0{space*4}{reverse off}{arrow left}$b0 now has #$0400"
1560 PRINT"{reverse on}{space*6}ldx #$03{space*3}":PRINT"{reverse on}lp1{space*3}ldy #$00{space*3}"
1570 PRINT"{reverse on}lp2{space*3}lda ($b0),y{reverse off}{arrow left} indirect indexed?":PRINT"{reverse on}{space*6}eor #$80{space*3}"
1580 PRINT"{reverse on}{space*6}sta ($b0),y{reverse off}{arrow left} indirect indexed!":PRINT"{reverse on}{space*6}dey{space*8}"
1590 PRINT"{reverse on}{space*6}bne lp2{space*4}":PRINT"{reverse on}{space*6}inc $b0 by #$100{reverse off}{arrow left}??*!!how??"
1600 PRINT"{reverse on}{space*6}dex{space*8}":PRINT"{reverse on}{space*6}bpl lp1{space*4}{reverse off}{arrow left}branch on plus!!"
1610 PRINT"{down}{reverse on}lda ($b0),y{reverse off} takes the contents of"
1620 PRINT"{down}memory loc'n $b0, adds y, and this{down}{left*4}{cm u*4}"
1625 PRINT"gives the address of the byte which "
1626 PRINT"{down}gets loaded into 'a'!!":GOSUB63000
1630 PRINT"{clear}there are some new ideas..and problems!"
1635 PRINT"{down*3}but first let's agree that we'll"
1636 PRINT"{down}use $b0 to refer to the memory loc'n"
1637 PRINT"{down}and ($b0) to refer to the {reverse on}contents"
1638 PRINT"{down}of memory location $b0."
1640 PRINT"{down*3}{reverse on}let's look at addressing modes{reverse off}:":GOSUB63000
1650 PRINT"{clear}basic"TAB(20)"assembler"
1655 PRINT"{cm u*5}"TAB(20)"{cm u*9}"
1660 PRINT"{reverse on}a=5{reverse off}"TAB(20)"{reverse on}lda #$05{reverse off}"
1670 PRINT"{down}Qimmediate mode. the accumulator"
1680 PRINT"is loaded with the # 5."
1690 PRINT"{down}{reverse on}a=m(5){reverse off}"TAB(20)"{reverse on}lda $05{reverse off}"
1700 PRINT"{down}Qabsolute addressing. 'a' is"
1710 PRINT"loaded with the contents of"
1720 PRINT"memory location 5."
1730 PRINT"{down}{reverse on}a=m(5+x){reverse off}"TAB(20)"{reverse on}lda ${0*3}5,x"
1740 PRINT"{down}Qabsolute {reverse on}indexed{reverse off}. the contents"
1750 PRINT"of loc'n (5+x) are loaded into 'a'."
1760 PRINT"{down}{reverse on}a=m(m(5+x)){reverse off}"TAB(20)"{reverse on}lda (${0*3}5,x)"
1770 PRINT"{down}Qindexed {reverse on}indirect{reverse off}. the contents"
1780 PRINT"of loc'n (5+x) give the address of"
1790 PRINT"the byte to be loaded into 'a'.":GOSUB63000
1800 PRINT"{clear}then there's our friend:"
1810 PRINT"{down}{reverse on}a=m(m(5)+y){reverse off}"TAB(20)"{reverse on}lda ($05),y{reverse off}"
1820 PRINT"{down}Q{reverse on}indirect indexed{reverse off}. first, the contents"
1830 PRINT"{down}of loc'n 5 are extracted.then 'y'"
1840 PRINT"{down}is added and the result gives the"
1850 PRINT"{down}address of the byte loaded into 'a'.":GOSUB63000
1860 PRINT"{clear}Q{reverse on}indirect{reverse off} means we go to a memory loc'n"
1870 PRINT"{down}to get the address of the byte to be"
1880 PRINT"{down}loaded into the accumulator."
1890 PRINT"{down}Q{reverse on}indexed{reverse off} means we add the contents"
1900 PRINT"{down}of a {reverse on}6510{reverse off} register to an address."
1910 PRINT"{down}Qif we {reverse on}index{reverse off} then {reverse on}indirect{reverse off} it's"
1920 PRINT"{down}{reverse on}indexed indirect{reverse off}..as in {reverse on}lda ($0400,x)"
1930 PRINT"{down}Qif we {reverse on}indirect{reverse off} then {reverse on}index{reverse off} it's"
1940 PRINT"{down}{reverse on}indirect indexed{reverse off}..as in {reverse on}lda ($b0),y":GOSUB63000
1950 ms$="clear?!*$&":GOSUB63100:GOSUB63000
1960 PRINT"{clear}let's explain about {reverse on}memory{reverse off}."
1970 PRINT"{down}{reverse on}6510{reverse off} instructions are stored in memory"
1980 PRINT"as 1- or 2- or 3- hex bytes."
1990 PRINT"{down}{reverse on}inx{reverse off}={reverse on}e8{reverse off} is one byte long
2000 PRINT"{down}{reverse on}lda #$05{reverse off}={reverse on}ad 05{reverse off} is two bytes"
2010 PRINT"{down}{reverse on}lda $1234,x{reverse off}={reverse on}bd 34 12{reverse off} is three bytes."
2020 PRINT"{space*15}^^ ^^"
2030 PRINT"in general, 2-byte addresses are"
2040 PRINT"stored in memory in reverse order:"
2050 PRINT"{reverse on}lo-byte{reverse off} then {reverse on}hi-byte{reverse off}."
2060 PRINT"{down}so if you have:"
2070 PRINT"{reverse on}lda ($b0),y{reverse off}={reverse on}b1 ca{reverse off} the 6510 will"
2080 PRINT"get from $b0 the {reverse on}lo-byte{reverse off} of the"
2090 PRINT"address,and from $b1 the {reverse on}hi-byte{reverse off}!"
2100 PRINT"{down}Qbe sure to put both bytes in $b0/$b1"
2110 PRINT"before {reverse on}lda ($b0),y{reverse off}!!":GOSUB63000
2120 PRINT"{clear}let's get back to:"
2130 PRINT"{down}{reverse on}begin lda #$0400 {reverse off}{arrow left}??*!#$0400 too big!!"
2140 PRINT"{reverse on}{space*6}sta $b0{space*4}{reverse off}{arrow left}$b0 now has #$0400"
2150 PRINT"{reverse on}{space*6}ldx #$03{space*3}":PRINT"{reverse on}lp1{space*3}ldy #$00{space*3}"
2160 PRINT"{reverse on}lp2{space*3}lda ($b0),y{reverse off}{arrow left} indirect indexed?":PRINT"{reverse on}{space*6}eor #$80{space*3}"
2170 PRINT"{reverse on}{space*6}sta ($b0),y{reverse off}{arrow left} indirect indexed!":PRINT"{reverse on}{space*6}dey{space*8}"
2180 PRINT"{reverse on}{space*6}bne lp2{space*4}":PRINT"{reverse on}{space*6}inc $b0 by #$100{reverse off}{arrow left}??*!!how??"
2190 PRINT"{reverse on}{space*6}dex{space*8}":PRINT"{reverse on}{space*6}bpl lp1{space*4}{reverse off}{arrow left}branch on plus!!"
2200 PRINT"{down}we now must put $0400 into $b0/$b1"
2210 PRINT"with {reverse on}lda #$00{reverse off} {reverse on}sta $b0{reverse off} {reverse on}lda #$04{reverse off} {reverse on}sta $b1{reverse off}."
2220 PRINT"{down}also {reverse on}inc $b0 by #$100{reverse off} is changed to:"
2230 PRINT"{reverse on}inc $b1{reverse off}{.*3} we need only {reverse on}inc{reverse off} the"
2240 PRINT"hi-byte by '1'!":GOSUB63000
2250 PRINT"{clear}we'll change our program to:"
2260 PRINT"{down}{reverse on}begin lda #$00{space*3}{reverse off}":PRINT"{reverse on}{space*6}sta $b0{space*4}"
2270 PRINT"{reverse on}{space*6}lda #$04{space*3}":PRINT"{reverse on}{space*6}sta $b1{space*4}"
2280 PRINT"{reverse on}{space*6}ldx #$03{space*3}":PRINT"{reverse on}lp1{space*3}ldy #$00{space*3}"
2290 PRINT"{reverse on}lp2{space*3}lda ($b0),y{reverse off}":PRINT"{reverse on}{space*6}eor #$80{space*3}"
2300 PRINT"{reverse on}{space*6}sta ($b0),y{reverse off}":PRINT"{reverse on}{space*6}dey{space*8}"
2310 PRINT"{reverse on}{space*6}bne lp2{space*4}":PRINT"{reverse on}{space*6}inc $b1{space*4}"
2320 PRINT"{reverse on}{space*6}dex{space*8}":PRINT"{reverse on}{space*6}bpl lp1{space*4}{reverse off}":GOSUB63000
2330 PRINT"{home}{down*17}we needn't {reverse on}ldy #$00{reverse off} each"
2340 PRINT"{down}time we {reverse on}bpl lp1":PRINT"{down}y=0 already so:":GOSUB63010
2350 PRINT"{home}{down*7}{reverse on}{space*5}":PRINT"{reverse on}loop":PRINT"{down*3}{right*10}{reverse on}loop"
2355 PRINT"{down*2}{right*10}{reverse on}loop":GOSUB63000
2360 PRINT"{home}{down*16}":FORi=1TO6:PRINTcl$:NEXT
2370 PRINT"{home}{down*17}note that {reverse on}ldx #$03{reverse off} can"
2380 PRINT"{down}be changed to anything from"
2390 PRINT"{down}{reverse on}ldx #$01{reverse off} to {reverse on}ldx #$80{reverse off}.":GOSUB63000
2400 PRINT"{home}{down*16}":FORi=1TO6:PRINTcl$:NEXT
2410 PRINT"{home}{down*17}for {reverse on}ldx #$00{reverse off} we'll x-loop once anyway!"
2420 PRINT"for {reverse on}ldx #$81{reverse off},or higher,{reverse on}dex{reverse off}"
2430 PRINT"will leave 'msb'=1 in the x-register"
2440 PRINT"and x<0 will result and {reverse on}bpl{reverse off} will"
2450 PRINT"{reverse on}not{reverse off} take us back to 'loop'!":GOSUB63000
2460 PRINT"{home}{down*16}":FORi=1TO6:PRINTcl$:NEXT
2470 PRINT"{home}{down*17}note that ($b1) will not"
2480 PRINT"{reverse on}overflow{reverse off} after a number of {reverse on}inc $b1{reverse off}"
2490 PRINT"instr'ns. after all,memory only goes"
2500 PRINT"to ${f*4}, so, unless you goof"
2510 PRINT"($b1)<=ff will always be true!":GOSUB63000
2520 PRINT"{clear}note that incrementing the address"
2530 PRINT"in $b0/$b1 by $0100 only requires"
2540 PRINT"{reverse on}inc $b1{reverse off}. if you want to increment"
2550 PRINT"by ${0*3}1 you can do it this way:"
2560 PRINT"{down}{reverse on}{space*5}{-*7} "
2570 PRINT"{reverse on}{space*5}inc $b0 ":PRINT"{reverse on}{space*5}bne next":PRINT"{reverse on}{space*5}inc $b1 "
2580 PRINT"{reverse on}next {-*7} "
2590 PRINT"{down}this adds '1' to ($b0).if it doesn't"
2600 PRINT"{reverse on}overflow{reverse off} from ff to 00 we continue"
2610 PRINT"with the 'next' intruction."
2620 PRINT"{down}if it does overflow to {reverse on}00{reverse off}"
2630 PRINT"the {reverse on}bne next{reverse off} will not take us to"
2640 PRINT"'next', and we add '1' to the hi-byte"
2650 PRINT"with {reverse on}inc $b1{reverse off}.":GOSUB63000
2660 PRINT"{clear}if you want to increment by other than"
2670 PRINT"{down}${0*3}1 or $0100 ({reverse on}inc $b0{reverse off} or {reverse on}inc $b1{reverse off})"
2680 PRINT"{down}then you need to {reverse on}add{reverse off} the increment."
2685 PRINT"{down}suppose we want to add $1f:"
2690 PRINT"{down}{reverse on}lda $b0 {reverse off}{arrow left}get lo-byte"
2700 PRINT"{reverse on}adc #$1f{reverse off}{arrow left}add #$1f to lo-byte"
2710 PRINT"{reverse on}sta $b0 {reverse off}{arrow left}put it back"
2720 PRINT"{reverse on}lda $b1 {reverse off}{arrow left}get hi-byte"
2730 PRINT"{reverse on}adc #$00{reverse off}{arrow left}add zero(?!)":PRINT"{reverse on}sta $b1 {reverse off}{arrow left}put it back"
2740 PRINT"{down}you see..adding #$1f might just cause"
2750 PRINT"the contents of $b0 to {reverse on}overflow{reverse off} which"
2760 PRINT"causes {reverse on}carry{reverse off}=1. so we add the carry"
2770 PRINT"to ($b1) with {reverse on}lda $b1{reverse off} & {reverse on}adc #$00"
2780 PRINT"{down}note{down}{left*4}{cm u*4}{up}:{reverse on}adc{reverse off} means {reverse on}ad{reverse off}d with {reverse on}c{reverse off}arry.":GOSUB63000
2790 PRINT"{home}{down*14}":FORi=1TO8:PRINTcl$:NEXT:PRINT"{home}{down*14}"
2800 PRINT"of course the {reverse on}carry{reverse off} may be {reverse on}1{reverse off} when"
2810 PRINT"{down}the above piece of code starts, so"
2820 PRINT"{down}we must always{down}{left*6}{cm u*6}{up} {reverse on}clc{reverse off} before an {reverse on}adc{reverse off}!":GOSUB63010
2830 PRINT"{home}{down*7}{reverse on}clc{space*5}":GOSUB63000
2840 PRINT"{clear}if you want to {reverse on}subtract{reverse off} {reverse on}#$1f{reverse off} you:"
2850 PRINT"{down*2}{reverse on}lda $b0 ":PRINT"{reverse on}sbc #$1f{reverse off}{arrow left}subtract $1f":PRINT"{reverse on}sta $b0 "
2860 PRINT"{reverse on}lda $b1 ":PRINT"{reverse on}sbc #$00{reverse off}{arrow left}subtract $00!!":PRINT"{reverse on}sta $b1 "
2870 PRINT"{down}note{down}{left*4}{cm u*4}{up}:{reverse on}sbc{reverse off} means {reverse on}s{reverse off}u{reverse on}b{reverse off}tract with {reverse on}c{reverse off}arry."
2880 PRINT"{down}however, with {reverse on}sbc{reverse off} you must have"
2890 PRINT"{down}carry=1 to start with!!":ms$="*?ugh!*?!!":GOSUB63000:GOSUB63100
2900 GOSUB63010:PRINT"{home}{down*2}{reverse on}sec{space*5}":GOSUB63000
3000 PRINT"{clear}":ms$="{reverse on}au revoir!{reverse off}":GOSUB63100:PRINT"{home}{down*2}":END
9999 GOTO9999
40098 POKEa(0),32:FORtt=1TOpp:NEXT:FORi=0TO6:POKEa(i+1),32
40099 POKEa(i),VAL(MID$(n$,i+1,1))+48:FORtt=1TOpp:NEXT:NEXT:POKEa(7),48:RETURN
40110 FORi=0TO7:POKEa(i),160:FORtt=1TOpp:NEXT
40111 POKEa(i),VAL(MID$(n$,i+1,1))+48:NEXT:RETURN
40120 FORi=0TO7:POKEp(i),160:FORtt=1TOpp:NEXT
40121 POKEp(i),VAL(MID$(n$,i+1,1))+48:NEXT:RETURN
40130 FORi=0TO7:POKEx(i),160:FORtt=1TOpp:NEXT
40131 POKEx(i),VAL(MID$(n$,i+1,1))+48:NEXT:RETURN
40140 FORi=0TO7:POKEy(i),160:FORtt=1TOpp:NEXT
40141 POKEy(i),VAL(MID$(n$,i+1,1))+48:NEXT:RETURN
40160 FORi=0TO7:POKEm(i),160:FORtt=1TOpp:NEXT
40161 POKEm(i),VAL(MID$(n$,i+1,1))+48:NEXT:RETURN
41120 FORi=0TO7:POKEp(i),160:FORtt=1TOpp:NEXT
41121 POKEp(i),PEEK(a(i)):NEXT:RETURN
41130 FORi=0TO7:POKEx(i),160:FORtt=1TOpp:NEXT
41131 POKEx(i),PEEK(a(i)):NEXT:RETURN
41140 FORi=0TO7:POKEy(i),160:FORtt=1TOpp:NEXT
41141 POKEy(i),PEEK(a(i)):NEXT:RETURN
41160 FORi=0TO7:POKEm(i),160:FORtt=1TOpp:NEXT
41161 POKEm(i),PEEK(a(i)):NEXT:RETURN
41340 FORi=0TO7:POKEa(i),160:FORtt=1TOpp:NEXT
41341 POKEa(i),PEEK(x(i)):NEXT:RETURN
41360 FORi=0TO7:POKEm(i),160:FORtt=1TOpp:NEXT
41361 POKEm(i),PEEK(x(i)):NEXT:RETURN
41410 FORi=0TO7:POKEa(i),160:FORtt=1TOpp:NEXT
41411 POKEa(i),PEEK(y(i)):NEXT:RETURN
41460 FORi=0TO7:POKEm(i),160:FORtt=1TOpp:NEXT
41461 POKEm(i),PEEK(y(i)):NEXT:RETURN
60000 r$="{cm a}{sh asterisk}{cm r}{sh asterisk}{cm r}{sh asterisk}{cm r}{sh asterisk}{cm r}{sh asterisk}{cm r}{sh asterisk}{cm r}{sh asterisk}{cm r}{sh asterisk}{cm s}{down}{left*17}{sh -}{sh space}{sh -}{sh space}{sh -}{sh space}{sh -}{sh space}{sh -}{sh space}{sh -}{sh space}{sh -}{sh space}{sh -}{sh space}{sh -}{down}"
60001 r$=r$+"{left*17}{cm z}{sh asterisk}{cm e}{sh asterisk}{cm e}{sh asterisk}{cm e}{sh asterisk}{cm e}{sh asterisk}{cm e}{sh asterisk}{cm e}{sh asterisk}{cm e}{sh asterisk}{cm x}"
60002 a$="{home}{down} {reverse on}a{reverse off}{up}"+r$:p$="{home}{down}{right*20}{reverse on}p{reverse off}{up}"+r$
60003 x$="{home}{down*4} {reverse on}x{reverse off}{up}"+r$:y$="{home}{down*4}{right*21}{reverse on}y{reverse off}{up}"+r$
60004 m$="{home}{down*7}{right*21}{reverse on}m{reverse off}{up}"+r$
60005 cr$="{home}{down*6}{cm a}{sh asterisk}{cm s}{down}{left*3}{sh -}{right}{sh -}{down}{left*3}{cm z}{sh asterisk}{cm x}"
60006 cc$="{home}{down} {reverse on}a{reverse off}{sh -}{down}{left*3} {down}{left} {down}{left} {down}{left} {down}{left}{space*3}{down}{left*3}{space*3}{down}{left*3}{space*3}{up}{space*12}"
60007 wd=40:crt=1024:PRINTCHR$(142)
60008 FORi=0TO7:a(i)=crt+wd+3+2*i:p(i)=a(i)+20:x(i)=a(i)+3*wd:y(i)=x(i)+20
60009 m(i)=y(i)+3*wd:NEXT:c=crt+7*wd+1
60010 sd$="{home}{down*9}":cl$="":FORi=1TOwd-2:cl$=cl$+" ":NEXT
60011 bt$="{home}":FORi=1TO24:bt$=bt$+"{down}":NEXT
60012 c$=cr$+"{home}{down}{cm a}{sh asterisk}{cm w}{down}{left*3}{sh -}{down}{left}{sh -}{down}{left}{sh -}{down}{left}{sh -}{down}{left}{cm q}{down}{right*4}{arrow left}carry bit"
60019 ml$="{home}{down*9}{right*27}"
60020 pp=20
60051 bt$="{home}":FORi=1TO24:bt$=bt$+"{down}":NEXT
60052 pt$="{red}{cm a}{sh asterisk*10}{cm s}{down}{left*12}{sh -}{right*10}{sh -}{down}{left*12}{cm z}{cm r}{sh asterisk*8}{cm r}{cm x}"
60053 pt$=pt$+"{down}{left*13}N{cm t*12}M{down}{left*14}{cm g}{=*12}{cm m}"
60054 pt$=pt$+"{down}{left*14}PO{cm t*10}PO{up*4}{left*12}"
60055 pt$=bt$+"{up*6}{right*26}"+pt$+"{black}"
60056 ml$="{home}{down*9}{right*27}"
60057 wd=40:crt=1024:PRINTCHR$(142)
60058 w2=wd/2:w3=wd-1:w1$=MID$(STR$(wd),2):
60059 w2$=MID$(STR$(w2),2):w3$=MID$(STR$(w3),2)
60100 RETURN
63000 PRINTbt$cl$;
63001 PRINTbt$"{reverse on}return{reverse off} to continue";
63002 GETz$:IFz$<>""THEN63002
63003 GETz$:IFz$=""THEN63003
63004 RETURN
63010 PRINTbt$cl$;
63011 PRINTbt$"{cm +*8}{reverse on}return to see it happen{reverse off}{cm +*8}";
63012 GETz$:IFz$<>""THEN63012
63013 GETz$:IFz$=""THEN63013
63014 RETURN
63100 FORt=1TO5:PRINTpt$ms$;
63101 PRINTpt$"{space*10}";
63102 PRINTpt$ms$;:NEXT
63103 RETURN
63200 GOSUB63000
63201 PRINTsd$;:FORt=1TO10:PRINTcl$:NEXT:PRINTsd$;:RETURN
63300 GOSUB63100:GOSUB63010:RETURN
63999 GOSUB60000:PRINT"{clear}":GOTO1630
stop tok64
(bastext 1.0)