CSCI 162 Spring 2018: Marie Lab 2

CSCI 162 Spring 2018: Computer Architecture Lab 2: A Subroutine construct

(Feb 6 and 8) For this lab, you will write two MARIE assembly language programs.

Go to the MARIE option at Applications -> Other, or use the Marie web app

Write an assembler program that does the following:

has a hardcoded integer called "secret", stored in hex format
gets input from the user in decimal format
puts output in character format
plays "guess the integer" with the user: gets an input integer from the user, and responds 'L' if the secret is less, 'H' if the secret is more than the guess, and allows another guess. If the secret number is correctly guessed, then the program will print it out in decimal, then submit that number as a parameter to a function called double and prints out the returned value; then submits that value to double and prints the output of that call as well.

For example, if the secret hex number is D, then your guesses and output might be the following:

You can label the parts of the code that you jump to `if', `then', `else', and `endif', or use other labels that identify the conditions that the code fragment is meant to handle (such as guessIsLower or guessIsHigher or guessedCorrectly). Note that `skipcond 400' is the instruction for skipping the next instruction if the AC is zero.

The subroutine (function) should have label "double", and you use JnS to get there, and JumpI to return back to the line of code you left. Recall the label should leave room for a return address, as in

double,  hex 0
         load double_input
         subt zero
         store double_output
         JumpI double

The first line of "double" code is the spot to store the return address. After that is the code to double the value that is in double_input, and store it again in double_output. Then return where control left off before entering the subroutine by executing "JumpI double". (Note that the above code is not correctly doubling the value -- it is meant only as an example of how to formulate the code to which your program will "Jump and Store" or JnS.)

CSCI 162 Course Outline