How to create a program that examines test scores

Write an MC68000 program that will examine a list of test scores stored in memory.

Transfer any passing score (greater than or equal to 50) to a table in memory, and transfer

any failing score to another table in memory. Also, keep a count of the number of scores

in each table.

• Assume that twenty scores are stored in memory words starting at location $5000.

Define this table of words, and assign a label to it using the DS.W assembler

directive. (How do you force its location to $5000?)

• Store all passing scores in memory words starting at location $5100, and store all

failing scores starting at location $5200. Define these tables using DS.W

assembler directives.

• Store the final count for the number of passing scores in register D2 and the

number of failing scores in register D3.

• Start your program at location $800.

• Include all necessary global and local comments.

• Use numbers to represent addresses only in ORG directives; for other instructions,

use labels.

• Clear your tables of passing and failing scores using program instructions at the

start of your program, to prepare for repeat runs.

• Do not leave any blank words between scores in either table.

• Try your program several times, with different data

• The name of your program should be your last name or its first eight letters.

Submit your program file (with extension .X68) and representative results as a

hard copy in the class prior to the due date.

ORG $800

START

LEA PASSING,A1 ; load address of passing scores into A1

LEA FAILING,A2 ; load address of failing scores into A2

MOVE #20,D1 ; we will use D1 as a counter for the 20 positions

FILL

MOVE.W #0,(A1) ; clear the current position in the passing table

MOVE.W #0,(A2) ; clear the current position in the failing table

ADD #2,A1 ; go to next position in the passing table

ADD #2,A2 ; go to next position in the failing table

SUB #1,D1 ; decrement position counter

BNE FILL ; if it’s not zero, repeat

LEA SCORES,A0 ; load address of scores into A0

LEA PASSING,A1 ; load address of passing scores into A1

LEA FAILING,A2 ; load address of failing scores into A2

MOVE #0,D2 ; initialize number of passing scores to zero

MOVE #0,D3 ; initialize number of failing scores to zero

MOVE #20,D1 ; we will use D1 as a counter for the 20 scores

COUNT

MOVE.W (A0),D0 ; load a score from the array

CMP.W #50,D0 ; compare with 50 to see if it’s a passing or failing score

BLT FAIL ; if it’s lower than 50 it’s failing

MOVE.W D0,(A1) ; otherwise it’s a passing score, save it in the passing table

ADD #2,A1 ; increment the pointer to the next empty space in the passing table

ADD #1,D2 ; increment the number of passing scores

BRA NEXT ; go to next element by skipping the fail part

FAIL

MOVE.W D0,(A2) ; it’s a failing score, save it in the failing table

ADD #2,A2 ; increment the pointer to the next empty space in the failing table

ADD #1,D3 ; increment the number of failing scores

NEXT

ADD #2,A0 ; go to next score in the table

SUB #1,D1 ; decrement score counter

BNE COUNT ; if it’s not zero, repeat

MOVE.L #9,D0 ; end program

TRAP #15

ORG $5000

SCORES DS.W 20

ORG $5100

PASSING DS.W 20

ORG $5200

FAILING DS.W 20

END START

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