TRAPS and the RUNTIME STACK

Programming Lab #$6$

CEG $3310/5310$: Computer Organization

PURPOSE

In this lab you will learn how to write your own trap service routines. You will also learn how to write

subroutines that utilize the runtime stack.

ASSIGNMENT

Using the LC$-3$ simulator, you will construct an assembly$-$level program that prompts for options when

working with a linked list, like printing, adding, and removing items from the list. A sample execution and

equivalent C program are included.

PART $1$

To implement input.asm you must do the following:

$$ You must read a user's input of $2$ digit decimal numbers. You are encouraged to reuse code you

wrote for Lab $3.$

$$ Once you have the decimal value you must load the final value into R$0$

$$ For example: if a user types the ASCII characters $31$ then at the end of your TRAP call R$0$ must

contain the value $0$x$001$F$$ in hexadecimal.

$$ This TRAP call should function properly even after being called multiple times, you will need to

call this TRAP function multiple times to complete this lab.

To implement output.asm you must do the following:

$$ Using R$0$ you must print the decimal value loaded into R$0$ to the console

$$ For example if the hex value in R$0$ is $0$x$0028$ then the console window should display the

characters $40$

To allow these trap routines to be useful, you must add them to the trap vector table.

$$ To add a trap service routine to the trap vector table, it must have it$$s own unique starting

address $($x$4000$ for input.asm and x$5000$ for output.asm$)$

$$ This starting address must be added to the trap vector table $($x$40$ for input and x$41$ for output$)$

$$ You must submit multiple programs for your final lab submission

PART $2$

Once your trap service routines are added to the trap vector table, you can implement the main program

loop of your linked list program.

$$ Setup your runtime stack for the main function as described in the sample C code

$$ Do not create custom subroutines for printf, scanf, malloc, or free. You must still be able

to print information to the user and read the user$$s input.

$$ Prompt the user to make a selection from the choices of print, add, remove, or quit.

$$ If the user selects add or remove, prompt the user to type a number to add or remove.

$$ Use your trap service routines to capture the value entered

$$ Pass the value entered to your

$$ If the user selects print, add, or remove setup your runtime stack to call the functions as

described in the sample C code.

$$ Implement the assembly equivalent of the functions for print, add, and remove, from

the C code as subroutines.

$$ Any required arguments must be passed to the functions through the runtime stack.

$$ If the user quits, pop your runtime stack and halt the processor.

NOTE

$$ You will have to submit multiple programs $($at least $3$ independent programs required i$.$e$.$ main,

input, and output. Using more than $3$ programs is acceptable.$)$

$$ The add and remove functions must accept a double pointer $($a pointer to a pointer$)$ for your

linked list. This allows removal of the head of the linked list and the creation of the head of the

linked list when the head is nonexistent.