VIRTUAL MACHINE

Task 1:

Write a program that will read in numbers until the value -1 is entered on the keyboard. Call this

program project1.asm

Task 2:

Make a copy of your project1.asm file called project2.asm using cp project1.asm project2.asm on the shell

command line. This program should read in numbers until -1 is entered and then display the sum of all

single digit numbers that were entered.

Task 3:

Make a copy of project2.asm and call it project3.asm. This final version should read in all values and AFTER

the -1 is entered, it should display all of the numbers entered followed by printing out the sum of these

numbers. The stack must be used.

VIRTUAL MACHINE INSTRUCTIONS

Instructions

ADD (1, ACC = ACC +arg)

BR (1, jump to arg)

BRNEG (1, jump to arg if ACC<0)

BRZNEG (1, jump to arg if ACC<= 0)

BRPOS (1, jump to arg if ACC>0)

BRZPOS (1, jump to arg if ACC>= 0)

BRZERO (1, jump to arg if ACC == 0)

COPY (2, arg1 = arg2)

DIV (1, ACC = ACC / arg)

MULT (1, ACC = ACC * arg)

READ (1, arg=input integer)

WRITE (1, put arg to output as integer)

STOP (0, stop program)

STORE (1, arg = ACC)

SUB (1, ACC = ACC - arg)

NOOP (0, nothing)

LOAD (1, ACC=arg)

ADD, DIV, MULT, WRITE, LOAD, SUB can take either variable or immediate value

as the arg: immediate value is positive integer or negative integer

- PUSH (0, tos++)

- POP (0, tos)

- STACKW (1,stack[tos-arg]=ACC)

- STACKR (1,ACC=stack[tos-arg])

- PUSH/POP are only means to reserve/delete automatic storage.

- STACKW/STACKR n - these are stack write/read instructions. n must be a non-negative number, and the access is to nth element down from TOS, top of stack.

NOTE: tos points to the topmost element on the stack

Storage directives

XXX val

XXX is a name

val is the initial value

all storage and ACC size are signed 2 bytes

Storage name and label are all names starting with latter and following with letters and digits up to eight total

Assumptions

1. any proper format within line, tokens separated by BS, blank space

2. all storage directives are listed following the last STOP

3. all names start with letters and contain more letters or digits

3 Invocation

>v i r t M a c h //read from s t d i n

>v i r t M a c h f i l e . asm //read from f i l e . asm

EXAMPLE:

Example:

sumOf3.asm

reads 3 arguments and returns the sum using a stack

READ X

PUSH

LOAD X

STACKW 0

READ X

PUSH

LOAD X

STACKW 0

READ X

STACKR 1

ADD X

STORE X

STACKR 0

ADD X

STORE X

WRITE X

POP

POP

STOP

X 0

Example:

sum3nostack.asm