SMLS (simple machine language simulator)

About

The simple machine language simulator (smls) is an interpreter of a simple assembly language (developed for CPU lessons), it can be used as a starting point to learn an assembly language or introduction to programming. The language is described in [1].

Features

• Designed for use with students, easy and simple.
• Simple configurations available by config.txt file.
• Run on Linux/UNIX and MS Windows.
• No limit of lines of code.
• Auto detects the language and shows according message.
  • Supported languages: English and Portuguese.

The Language

Available instructions (Table from [1]):

This language uses a very simple CPU with only one Accumulator. Some instructions, like LOAD and ADD, use as an operand a memory address or a number; when operand is a number you need to put the character '#' before it (i.e. LOAD #30).

More info in [1].

Examples

1. Calculate 30 + 40 and store the result in address 100.

     LOAD #30
     ADD #40
     STORE 100
   

2. Sum the memory address 30 and 31 and store the result in address 32.

     load 30
     add 31
     store 32
   

3. Update the value of memory address 60 by subtracting its value in two.

     LOAD 60
     SUB #2
     STORE 60
   

4. Write the numbers [1, 3] in memory range [20, 22].

     % op-codes are case free
     load #1
     store 20
     add #1
     store 21
     add #1
     store 22
   

5. Sum the numbers [1, 10] and store the result in address 50.

     load #0
     store 49        % partial sum
     load #1
     store 15        % tmp counter
     equal #11
     jump #10        % jump to line 10 (jump ignore comment lines and empty lines)
     
     load 49
     store 50
     halt
     
     load 49
     add 15
     store 49
     load 15
     add #1
     store 15
     jump #5
   

How to Use smls

First, you need to write the code. The code can be written in a simple editor, like nano or notepad (if you are using Windows), after that you can execute your code using smls. You can add comments to your program using the character % at start of line.

1. Write code.
2. Run code in smls.
   1. Linux/UNIX:

        smls file
      

   2. Windows*

        smls.exe file
      

      1. If you are using MS Windows, you need to use command prompt (MSDOS) to run smls, to help it use 'run_smls.bat'.

By default, smls:

• Show each line of code before executing it. If any error occurs, the program will be stopped.

• By default, the smls only executes the code and print each line, no result is displayed. To see results you can: (1) display the contents of memory, (2) show the accumulator value; also you can show the runtime. To use these resources you need to create a simple file, in your current directory, named 'config.txt', and in the 'config.txt' you enter the options described below.

config.txt

If this file exists in the current path, it will be read by smls.

Lines starting with % are ignored. 0 = disabled, 1 = enabled.

options:

  m START END (show memory) [DEFAULT=none]
  This command displays the memory data between START END at the end of the program.
  You can use this command several times in config.txt
  
  a 0/1 (show the value of accumulator) [DEFAULT=0]
  
  t 0/1 (show the runtime) [DEFAULT=0]
  
  i 0/1 (show the lines of program that will be executed) [DEFAULT=1]
  
  lang auto/pt/en (the language of program) [DEFAULT=auto]
  
  sln 0/1 (show line number) [DEFAULT=0]
  If this option is equal 1 the user program will be only printed on the screen
  and the program will not be executed; useful when you are using commands like EQUAL and JMP.

In [3] you can see an example of 'config.txt'.

Download

The smls supports Linux/UNIX and Windows.

binary smls for Windows (installer: do not need admin rights) (MD5 2c4098171d6f13566be0b8f05a48b98d)

binary smls for Debian/Ubuntu 32 bits (MD5 dc1caddc76cf3a08f0a2e77ad7abadfc)

binary smls for Debian/Ubuntu 64 bits (MD5 dffc22e39d7c85e8689217af3ce26509)

source code (MD5 960799d4479bddd6d15414c09c341e32)

To use smls in others systems, get the source code and compile it.

For Teachers

Before start using this program with your students, I recommend:

1. Teach the language.
2. Practice on paper some examples and programs. Use binary form (with op-codes and operands, see Instruction format), next use instructions with mnemonics.
3. In the computer lab:
   1. Run a very simple program [2].
   2. Talk about the config file (config.txt)
      1. Display the memory data with the command 'm START END'.
      2. Notice that memory contents are random, and students can see this by running the same program multiple times.
      3. Use the command STORE to save data into the memory, show this.
      4. You can use the command 'm START END' multiple times in 'config.txt', show this too.
   3. Enable accumulator in 'config.txt'.
   4. Use % (comment) in your programs.

Prepared exercises: If you are a teacher I can send to you some exercises to you use in your class, just mail me.

Instruction format

Number bit: if equal 1, the operand is a number (Image from [1]).

Contribute

• If you want your language supported in the program, please send me a mail.

Help and more info

Please send me a mail.

Author

Marcos Talau (talau@users.sf.net)

References

[1]

Osman Balci; William S. Gilley; Robin J. Adams; Emre Tunar; N. Dwight Barnette

http://courses.cs.vt.edu/csonline/MachineArchitecture/Lessons/CPU/Lesson.html

[2]

  LOAD #10
  STORE 0

[3]

  %%% Lines starting with % are comments
  %%% Options: 0 = disabled, 1 = enabled
  
  %% will show the memory data between 0 100 at the end of program
  %m 0 100
  
  %% 1=show the value of accumulator (default 0)
  %a 1
  
  %% 1=show the runtime (default 0)
  %t 1
  
  %% show the line numbers of program and exits, command useful when you
  %% are using commands like EQUAL and JMP (default 0)
  %sln 1
  
  %% 0=not show the lines of code (default 1)
  %i 0
  
  %% the language of this program (default auto)
  %lang en
  %lang pt