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Programmer
Join Date: Sep 2005
Posts: 69
Rep Power: 3 
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assembly questions
this is one of the first code examples i've used to take a peek into assembly programming. this one i can't quite figure out. basically, i have made a X.txt file that has coordinates of points that make a star. the program asks user to input the name of the file where the coordinates are located, it draws the star using different colors, and it computes the sum of all xxxx and yyyy coordinates. there are plenty of values in hex form that don't make sense to me, i can't figure out why they're THERE that is. also, i can't figure out what is the function of each of those labels. i understand every line of code, what it does to be exact, but my brain can't compile it as a whole.  i've marked the parts i don't understand (not all of it though) in red, bold font. so if you have the nerves, please hit me up with some info. thank you all for your time
START ORG $1000
MOVE.L #23,D1
LEA text1,A1 *get adress of tekst1, store in A1
MOVE #1,D0 *print the text from (A1), without CR, LF.
TRAP #15 *activates I/O
MOVE.L #$2000,A1
MOVE #2,D0 *input char via keyboard
TRAP #15
MOVE #51,D0 *open existing file
TRAP #15
MOVE.L #$2300,A0
MOVE.L #$2010,A1
MOVE.L #$500,D2
MOVE #53,D0 *set number of chars for "reading"
TRAP #15
MOVE.L #$208E, A2
MOVE.L #$200E, A1
MOVE.L #$201E, A3
MOVE.L #$2100, A5
MOVE.L #$2110, A6
Y1 MOVE.L #$00000000,D7
JMP X2
X1 MOVE.L #$00000000,D7
ADD #$2,A1
ADD #$2,A2
MOVE.B (A1),D7
CMP #$2E,D7
SUB #$30,D7
MULU #100,D7
ADD #$1,A1
MOVE.B (A1),D6
SUB #$30,D6
MULU #10,D6
ADD #$1,A1
MOVE.B (A1),D5
SUB #$30,D5
ADD D5,D6
ADD D6,D7
MOVE.W D7,(A2)
JMP K2
K1 MOVE.L #$00000000,A4
ADD D7,(A0)
SUB #$8,A0
SUB #$8,A0
JMP K3
K2 CMP #$00000000,A4
BNE K1
ADD D7,(A0)
MOVE.L #$00000001,A4
ADD #$10,A0
K3 MOVE.B D5,D0
X2 CMP A3,A1
BNE X1
MOVE.L A1,A7
ADD #$2,A7
MOVE.B (A7),D1
JMP X3
X4 MOVE.L #$0000FF00,D1
JMP X5
X3 CMP #$31,D1
BEQ X4
JMP X6
X7 MOVE.L #$000000FF,D1
JMP X5
X6 CMP #$32,D1
BEQ X7
JMP X8
X9 MOVE.L #$00FF0000,D1
JMP X5
X8 CMP #$33,D1
BEQ X9
JMP X10
X11 MOVE.L #$00FF00FF,D1
JMP X5
X10 CMP #$34,D1
BEQ X11
X5 MOVE #80,D0
TRAP #15
MOVE.L #$2090,A2
MOVE.W (A5),D1
CMP #$0,D1
BNE J1
MOVE.W (A2),D1
ADD #$2,A2
MOVE.W (A2),D2
ADD #$2,A2
J1 MOVE.W (A2),D3
ADD #$2,A2
MOVE.W (A2),D4
MOVE.W (A5),D5
JMP J3
J2 MOVE.W (A6),D1
JMP J4
J3 CMP #$0,D5
BNE J2
J4 MOVE #84,D0
TRAP #15
MOVE.L #$00000000,D1
MOVE.L D3,D1
MOVE.L D4,D2
MOVE.W D1,(A6)
ADD #$2, A1
ADD #$A, A3
MOVE.L #$208E, A2
ADD #$1,(A5)
CMP #$A, (A5)
BNE Y1
move.l #$00000016,d1
move.l #11,d0
trap #15
MOVE.L #$17,D1
LEA text2,A1
MOVE.L #1,D0
TRAP #15
move.l #$00000000,d1
move.w (a0),d1
move #3,d0
trap #15
move.l #$00000017,d1
move.l #11,d0
trap #15
MOVE.L #$17,D1
LEA text3,A1
MOVE.L #1,D0
TRAP #15
add #$10,a0
move.l #$00000000,d1
move.w (a0),d1
move #3,d0
trap #15
MOVE.B #9,D0
TRAP #15 Halt Simulator
text1 DC.B 'File input: ',$D,$A,0
text2 DC.B 'Sum of x coordinates: ',$D,$A,0
text3 DC.B 'Sum of y coordinates: ',$D,$A,0
END START |