Updated: 2003-05-04 01:19

Project 2 - LMC Programming

DAT 2343 - Summer 2000

Synopsis

1. Write LMC mnemonic instructions for a program, using the supplied pseudo-code.
2. Assemble by hand your mnemonic instructions into LMC numeric codes.
3. Enter your codes and test your program in the LMC simulator under Windows.
4. Hand in an envelope containing a diskette and printout of your working program.

Program Description and Sample Input

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
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.

Pseudo-Code Algorithm

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
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.

Assembly and Debugging

Hand-assemble your LMC mnemonic instructions into the equivalent LMC numeric codes.  (Assign locations to all the instructions; build a label table; translate the mnemonics into LMC numeric codes.)

Download the "son of LMC" Simulator program (see below) that simulates the "Little Man Computer". This program should be run from Windows 95/98. Run the simulator and enter your numeric codes into the correct mailboxes. Run, test, and debug your program using the simulator.

When your program works correctly, use the simulator to save the numeric codes on a diskette, using the file name given below.

Be sure to resave your modified numeric codes if you make changes to the codes while in the simulator, and remember to modify your mnemonic instructions to reflect any such changes before you hand in your project.  The mnemonic instructions you hand in must match the numeric codes used in the simulator and saved on disk!

Submit an envelope containing a diskette containing a text file of your saved LMC numeric codes and a text file of your mnemonic instructions.  Also include one printed copy of the mnemonic instructions file on a sheet of paper.  Follow the Hand In format given below.

LMC Simulator under Windows

The simulator comes in two versions.  The basic version, available on Alan Pinck's site, is known to work reasonably under Windows 95/98.  The enhanced version was enhanced by Algonquin student Christopher Hyne and permits editing and other features.  I recommend you try the enhanced simulator first; if it misbehaves, tell me what went wrong and return to the basic simulator.

The Enhanced Simulator can read the data files saved by the Basic Simulator; but, the Basic Simulator can only read files saved in "old format".  (You will be asked which format you want when you use the "save" feature of the Enhanced Simulator.)  You may submit files on diskette in either format.  Enhanced format is easier to read, since it is one mailbox per line.

Enhanced Simulator (FoSoLMC.EXE)

If you have Visual Basic 6.0 on your computer, you should only need the actual program executable, given above. If you don't have Visual Basic 6.0 or the Visual Basic Runtime Libraries on your computer you will need to download and install them using the (large!) Setup Kit available here.

The above links are local Algonquin copies of the original files kept on Christopher Hyne's FoSoLMC site.

Basic Simulator (SonOfLMC.EXE)

Use this Basic Simulator if you can't get the Enhanced Simulator to work.

The Basic Simulator doesn't have editing and other enhancements built in.  It requires certain Dynamic Link Libraries which are commonly installed on many systems (all Algonquin College lab computers should have these files). Specifically, this program was created using Visual Basic version 4 and needs VB40032.DLL.

If your computer does not have any of the required files, you can download a .ZIP version of the entire package including all support files from:

The available files include: SonOfLMC.ZIP... the complete executable package (4Mb) Son_P1.ZIP, Son_P2.ZIP, Son_P3.ZIP, Son_P4.ZIP... all the same files as the above but broken up into 4 collections, each of which should fit on a 1.4Mb disk.

Hand In

Submit your Project in a labelled, unsealed, but closed envelope.  (If you seal an envelope, it becomes useless as an envelope after I unseal it!)

Create and include in the envelope a copy of a diskette containing two text-only files:

1. File 1: A PROGRAM.TXT text file containing my Assignment Submission label information followed by the five-column (plus comments) code and mnemonic instructions of your LMC program.
2. File 2: A P2CODES.LMC "save" text file from the LMC simulator containing the LMC numeric codes of your assembled program.  I accept both Enhanced and Basic save formats.  I will load this code into my own simulator and test it.

Print the PROGRAM.TXT from the diskette and include the printout in the envelope:

1. Printout: Print a clear paper copy of your PROGRAM.TXT file for submission in the envelope along with your diskette.

Please keep master copies of the diskette and printout; don't hand in your only copy.

Text Files Only

For full marks:

 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.

Problems?

As with all questions and comments on course content, please post any problems to the course discussion news group.

 Web Author: Ian! D. Allen idallen@idallen.ca      Updated: 2003-05-04 01:19 Support free and non-commercial Internet. This site works best in Any Browser, a campaign for non-specific WWW. This work is licensed under a Creative Commons License.