LBS290F                                                      Fall 1991

                     ASSIGNMENT 19 - MACHINE LANGUAGE - II

Due Date: Extra Credit 5 points - anytime before the final

This program will implement a simple computer language.  This language is
similar to the lowest level language actually executed by computer hardware.

Your computer has 100 integer variables numbered from 1 through
100.

This language has the following statements:

        Statement            Action
        ---------            ----------------
        * Comment            Simply print out the comment
        E                    Echo every command
        N                    Don't Echo every command
        X or End of file     Exit
        R 10                 Read an integer value from input and
                             store in vars[10]
        P 10                 Print the contents of vars[10]
        10  S 100            Store 100 into vars[10]
        10  Q  20            vars[10] = sqrt( vars[20] );
        10  =  20  +  30     vars[10] = vars[20] + vars[30]
        10  =  20  -  30     vars[10] = vars[20] - vars[30]
        10  =  20  *  30     vars[10] = vars[20] * vars[30]
        10  =  20  /  30     vars[10] = vars[20] / vars[30]

The program should catch and print a message for the following errors:

        Z                    First letter illegal
        10 S                 Incorrect number of parameters
        10 >  20  +  30      Illegal Character
        10 =  20  >  30      Illegal operator

The file /usr/usrs/crs/assn19 has the following program:

  E
  * This is a program to calculate the determinant
  *
  * location 1 will store a
  * location 2 will store b
  * location 3 will store a
  * location 10 will be used for root 1
  * locations 90  and above will be temporary variables
  *
  * Enter the value for a
  R 1
  * Enter the value for b
  R 2
  * Enter the value for c
  R 3
  * Figure out B squared
  90 = 2 * 2
  * Figure out 4AC
  91 S 4
  91 = 91 * 1
  91 = 91 * 3
  * Figure out B squared - 4ac
  92 = 90 - 91
  * Take the square root
  92 Q 92
  * Figure out the top of the equation
  93 S -1
  94 = 2 * 93
  * Subtract the determinant
  94 = 94 - 92
  * Calculate 2 * A
  95 S 2
  95 = 95 * 1
  10 = 94 / 95
  P 10 
  X

When your program is running, try to execute this program using the
following command:

  $ a.out < /usr/usrs/crs/assn19

When you are prompted for a, b, and c, use 1 7 and 12.

The root printed should be 4.