Project 2 - LMC Programming

Your program should read a sequence of numbers (after all, the LMC can only input numbers!) and interpret the numbers alternately as numeric operands and numeric codes that indicate arithmetic operations to be performed on the numeric operands.

Keep a running total and output the results of the arithmetic (the running total) as you read each new numeric operand.  When the program is done, output a count of the number of numeric operands that were input.

For example, suppose we had the following sequence of input values:

    005 020 006 020 007 030 008 090

We want our program to interpret this 8-number sequence as the following 8-term formula:

    5 + 6 + 7 - 8 QUIT

To do this, our program must interpret every second input value as a code to perform an arithmetic operation.  Note how 020 stands for "+", 030 for "-", and 090 for "QUIT".  Here is the full table of numeric arithmetic operation codes to be recognized by our program:

      010 indicates a Reset-code
      020 indicates an Add-code
      030 indicates a Subtract-code
      090 indicates a Quit-code

Let's look at each of the eight input values in the above example. The odd-numbered input values are all numeric operands.  The even-numbered input values are all interpreted as arithmetic operation codes according to the given table.

1. 005 - The first input value to the program is always interpreted as a number that becomes the current running total. After reading this number, the program outputs the running total: 005.
2. 020 - The second input value is a code for an arithmetic operation to perform; in this case, 020 means an Add operation (+) that will use the next input number.
3. 006 - The third input value is the number to add to the current running total.  After reading and adding this number, the program outputs the new running total: 011.
4. 020 - The fourth input value is a code for an arithmetic operation to perform; in this case, 020 means another Add operation (+) that will use the next input number.
5. 007 - The fifth input value is the number to add to the current running total.  After reading and adding this number, the program outputs the new running total: 018.
6. 030 - The sixth input value is a code for an arithmetic operation to perform; in this case, 030 means a Subtract operation (-) that will use the next input number.
7. 008 - The seventh input value is the number to subtract from the current running total.  After reading and subtracting this number, the program outputs the new running total: 010.
8. 090 - The last input value is an operation code for "Quit the program".  After reading this code, the program outputs the count of numeric operands read - 004 - and stops.

Consider another example of four input values:

    020 020 020 090

Above, the arithmetic being performed is: 20 + 20 QUIT.  The running total output by the above example would be 020 and 040.  The count of the number of numeric operands read would be 002.

Here is another 8-number input example:

    005 020 006 010 007 030 008 090

Above, the arithmetic being performed is: 5 + 6 @ 7 - 8 QUIT, where @ stands for a reset operation (numeric code 010).  The reset operation sets the current running total to be the next input number (007), discarding the previous running total.  The running totals output by the above example would be 005, 011, 007, and 999.  (The 999 comes from 7-8.) The count of the number of numeric operands read would be 004.

Let's look at the pseudo-code that implements this program.

Use the following pseudo-code to develop your LMC mnemonic assembler program.

    Set the running total value to be zero
    Set the loop counter to be zero
    Set the operation code to be the Reset-code
    Do {
       input a number
       If the operation code equals the Add-code
          add the input number to the running total value
       ElseIf the operation code equals the Subtract-code
          subtract the input number from the running total value
       ElseIf the operation code equals the Reset-code
          set the running total value to be the input number
       Else
          set the running total value to be 999 (indicating an error)
       Endif
       output the running total value
       increment the loop counter
       input the next operation code
    } while the operation code is not equal to the Quit-code
    output the loop counter
    Stop

    Use the following constant values for your numeric operation codes:
      010 indicates a Reset-code
      020 indicates an Add-code
      030 indicates a Subtract-code
      090 indicates a Quit-code

Translate the given pseudo-code into LMC mnemonic instructions.  Pay attention to the details of the algorithm and the placement of each statement.

Your translated code must be in the usual labels/mnemonics/operands/comments format.  Do not optimize your code!  Translate each pseudo-code statement separately.

Important Notes

	Pick proper names for your variables.  Do not use poor names such as "first", "second", "A", "B", "number", "num1", "num2", or "value" (etc.).  Use good names that reflect the functions of the variables in the algorithm.
	Variable names and labels must start with a letter and may not contain blanks (same as in most programming languages).
	No numeric arguments/operands are allowed when writing LMC mnemonic instruction assembly language - write mnemonic instructions with labels only.  (For example, always write "LDA SUM" not "LDA 23".
	When writing mnemonic assembly language code using labels, ensure that all labels used have defined locations.
	You can't use the same name for two different variables and/or labels.  All names must be unique (same as in most programming languages).
	Do not use the ORG pseudo-instruction.  Code should begin at mailbox location zero.

	Follow my Assignment Submission Standards.  Put labels on everything!
	All the submission files on the diskette must be plain text only.  Plain text is readable in Windows Notepad or DOS EDIT (or Unix/Linux vi).  Check the format of your files before you submit them.  Do not submit Word, WordPerfect, or HTML documents.
	Use the exact file names given.  The automated program I use to mark these assignments will not find misspelled files on your diskette.  Do not place files in a subdirectory on the diskette.
	Ensure that the document prints neatly - pay attention to margins, line length, and consistent indentation.  Align the columns carefully.