Perform these steps using LC$-3$ assembly that does not reference the run time stack. Learning Subroutines

Programming Lab #$3$

CEG $3310/5310$: Computer Organization

PURPOSE

The average computer scientist programs in assembly very rarely. However, some familiarity with assembly level

programming is necessary to develop the fundamental understanding of how high$-$level programs get executed $($which

itself is necessary to understand high$-$end performance issues$).$ Subroutines are one of the most important fundamental

assembly language concepts.

ASSIGNMENT

In this lab you will create a simple calculator program. Calculator programs are common in higher level language

programming courses but implementing them in assembly is not so simple.

To create this calculator program you will have to implement $4$ subroutines:

$1.$ GETNUM

a$.$ Captures a positive two digit $(0-99)$ number from the keyboard

$2.$ GETOP

a$.$ Captures an operation from the keyboard $(+,-,$ or $*)$

$3.$ CALC

a$.$ Calculates the correct mathematical result when provided two positive two digit numbers and an

operation

$4.$ DISPLAY

a$.$ Displays up to a $4$ digit positive or negative number

In the main program loop, the program will prompt the user to enter the first number. After the user enters their first

number, the program will prompt the user for an operation $(+,-,*).$ Lastly, the program will prompt the user for the

second number. Using the first number, operation, and second number, the calculator program will display the

mathematical result. Once the output is displayed, the program will loop endlessly to allow the user to enter in more

combinations of numbers and operations.

For the subroutines in your program, use registers to take inputs and provide outputs. Do not implement a runtime stack

for this lab. As an example, the CALC subroutine could receive the first number on R$0,$ the second number on R$1,$ the

operation on R$2,$ and output the final result on R$0.$

A sample program is provided to get you started.

The following is an example output of the program:

Enter first number $(0-99)$: $5$

Enter an operation $(+,-,*)$: $-$

Enter second number $(0-99)$: $23$

Result: $-18$

Enter first number $(0-99)$: $75$

Enter an operation $(+,-,*)$: $*$

Enter second number $(0-99)$: $49$

Result: $3675$

Enter first number $(0-99)$: $50$

Enter an operation $(+,-,*)$: $+$

Enter second number $(0-99)$: $70$

Result: $120$