Assignment 15
Assignment
Write an MC68000 program that will print out the smaller of two numbers inputted from
the terminal. The program should prompt the user to input the numbers and then output
the result after a statement indicating the result.
The initial prompts can be “Please input the first number:” and “Please input the second
number:”. The output statement can be “The smaller of the two numbers is:”.
Submit your program file (with extension .X68) along with representative results with the
normal naming convention as paper copies in the class on or before the due date.
Solution
ORG $1000
FIRST: DC.B ‘Please input the first number: ‘
DC.B 0
DS.W 0
SECOND: DC.B ‘Please input the second number: ‘
DC.B 0
DS.W 0
OUTPUT: DC.B ‘The smaller of the two numbers is: ‘
DC.B 0
DS.W 0
ORG $1500
START: ; first instruction of program
MOVEA.L #FIRST,A1 ; prompt the user for the first number
MOVE.L #13,D0
TRAP #15
MOVE.L #4,D0 ; read a number from the user into D1.L
TRAP #15
MOVE.L D1,D2 ; save read number in D2 to use it later
MOVEA.L #SECOND,A1 ; prompt the user for the second number
MOVE.L #13,D0
TRAP #15
MOVE.L #4,D0 ; read another number from the user into D1.L
TRAP #15
MOVEA.L #OUTPUT,A1 ; print the output statement
MOVE.L #13,D0
TRAP #15
CMP.L D2,D1 ; compare the first number with the last one read
BLT D1SMALL ; if D1 is smaller, go to print D1
D2SMALL: ; else, D2 is smaller, print it
MOVE.L D2,D1 ; move D2 to D1 for printing it
MOVE.L #3,D0 ; print the number in D1.L using trap 15
TRAP #15
BRA EXIT ; exit the program
D1SMALL:
MOVE.L #3,D0 ; print the number in D1.L using trap 15
TRAP #15
EXIT:
MOVE.B #9,D0
TRAP #15 ; halt simulator
END START ; last line of source
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