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https://wiki.amstrad-cpc.net/index.php?title=Programming:Integer_Division&diff=10092
Programming:Integer Division
2006-09-21T14:20:50Z
<p>80.77.225.28: Added 8bit division</p>
<hr />
<div><br />
== 8bit division ==<br />
<br />
'''Input:''' HL=Value1, C=Value2<br />
<br />
'''Output:''' L=Value1/Value2, H=Value1 MOD Value2<br />
<br />
'''Destroyed:''' AF,BC<br />
<br />
<pre><br />
LD B,8<br />
Div_Next:<br />
ADD HL,HL<br />
LD A,H<br />
SUB C<br />
JR C,Div_NXTB<br />
LD H,A<br />
INC L<br />
Div_NXTB:<br />
DJNZ Div_Next<br />
RET<br />
</pre><br />
<br />
== 16bit division ==<br />
<br />
'''Input:''' BC=Value1, DE=Value2<br />
<br />
'''Output:''' HL=Value1/Value2, DE=Value1 MOD Value2<br />
<br />
'''Destroyed:''' AF,BC<br />
<br />
<pre><br />
clcd16 ld a,e<br />
or d<br />
ld hl,0<br />
ret z<br />
ld a,b<br />
ld b,16<br />
clcd161 rl c<br />
rla<br />
adc hl,hl<br />
sbc hl,de<br />
jr nc,clcd162<br />
add hl,de<br />
clcd162 ccf<br />
djnz clcd161<br />
ex de,hl<br />
rl c<br />
rla<br />
ld h,a<br />
ld l,c<br />
ret<br />
</pre><br />
<br />
== 24bit division ==<br />
<br />
'''Input:''' A,BC=Value1, DE=Value2<br />
<br />
'''Output:''' HL=Value1/Value2, DE=Value1 MOD Value2<br />
<br />
'''Destroyed:''' AF,BC,IX,IYL<br />
<br />
<pre><br />
clcdiv db #dd:ld l,e<br />
db #dd:ld h,d ;IX=Value2<br />
ld e,a ;E,BC=Value1(Counter)<br />
ld hl,0<br />
db #dd:ld a,l<br />
db #dd:or h<br />
ret z<br />
ld d,l ;D,HL=CalcVar<br />
db #fd:ld l,24 ;IYL=Counter<br />
clcdiv1 rl c<br />
rl b<br />
rl e<br />
rl l<br />
rl h<br />
rl d<br />
ld a,l<br />
db #dd:sub l<br />
ld l,a<br />
ld a,h<br />
db #dd:sbc h<br />
ld h,a<br />
ld a,d<br />
sbc 0<br />
ld d,a ;D,HL=D,HL-IX<br />
jr nc,clcdiv2<br />
ld a,l<br />
db #dd:add l<br />
ld l,a<br />
ld a,h<br />
db #dd:adc h<br />
ld h,a<br />
ld a,d<br />
adc 0<br />
ld d,a<br />
scf<br />
clcdiv2 ccf<br />
db #fd:dec l<br />
jr nz,clcdiv1<br />
ex de,hl ;DE=Value1 MOD Value2<br />
rl c<br />
rl b<br />
ld l,c<br />
ld h,b ;HL=Value1 DIV Value2<br />
ret<br />
</pre><br />
<br />
== 32bit division ==<br />
<br />
'''Input:''' IY,BC=Value1, IX=Value2<br />
<br />
'''Output:''' IY,BC=Value1/Value2, HL=Value1 MOD Value2<br />
<br />
'''Destroyed:''' AF,DE,IY<br />
<br />
<pre><br />
clcd32c db 0<br />
clcd32 ld hl,0<br />
db #dd:ld a,l<br />
db #dd:or h<br />
ret z ;IY,BC=Value1(Counter)<br />
ld de,0 ;DE,HL=CalcVar<br />
ld a,32 ;Set Counter to 32<br />
clcd321 ld (clcd32c),a<br />
rl c<br />
rl b<br />
db #fd:ld a,l:rla:db #fd:ld l,a<br />
db #fd:ld a,h:rla:db #fd:ld h,a<br />
rl l<br />
rl h<br />
rl e<br />
rl d<br />
ld a,l<br />
db #dd:sub l<br />
ld l,a<br />
ld a,h<br />
db #dd:sbc h<br />
ld h,a<br />
ld a,e<br />
sbc 0<br />
ld e,a<br />
ld a,d<br />
sbc 0<br />
ld d,a<br />
jr nc,clcd322<br />
ld a,l<br />
db #dd:add l<br />
ld l,a<br />
ld a,h<br />
db #dd:adc h<br />
ld h,a<br />
ld a,e<br />
adc 0<br />
ld e,a<br />
ld a,d<br />
adc 0<br />
ld d,a<br />
scf<br />
clcd322 ccf<br />
ld a,(clcd32c)<br />
dec a<br />
jr nz,clcd321 ;HL=Value1 MOD Value2<br />
rl c<br />
rl b<br />
db #fd:ld a,l:rla:db #fd:ld l,a<br />
db #fd:ld a,h:rla:db #fd:ld h,a<br />
ret ;IY,BC=Value1 DIV Value2<br />
</pre><br />
[[Category:Programming]]</div>
80.77.225.28