The Simpletron Simulator
                                   &
                          The Simple Compiler

Simpletron is a virtual machine invented by Deitel for his books.
Simpletron runs programs written in the Simpletron Machine Language, an
simple Machine Language.

An instruction (and data) in the Simpletron Machine Language is a signed
four-digit integer, like +1009. The first two digits are the opcode, and
the last two digits are the operand.

Simple Basic is a Basic-like programming language that compiles into
Simpletron Machine Language.


§ History

This software is a project done by me while reading «C: How to Program»,
by Deitel & Deitel.

The Simpletron Simulator first appeared as a code to be reviewed in
codereview.stackexchange:

	https://codereview.stackexchange.com/questions/239425

The Simple Basic Compiler first appeared as a code to be reviewed in
codereview.stackexchange:

	https://codereview.stackexchange.com/questions/239616


§ Files

The files are:
• ./include/memory.h:        Specify the memory size and the opcodes.
• ./simple/*:                The source code for the Simple Compiler.
• ./simple/simple.6          The manual for the Simple Compiler.
• ./simpletron/*:            The source code for the Simpletron Simulator.
• ./simpletron/simpletron.6: The manual for the Simpletron Simulator.
• ./samples/*.basic:         Sample files in simple basic to be compiled
                             to the Simpletron Machine Language.


§ Usage

To run a program 'file' written in the Simpletron Machine Language in
the simpletron simulator, use the simpletron(1) command as in.
│ simpletron file

You can use the option ‘-c’ to do a core dump after running it, and ‘-v’
to trace the execution and the registers of the Simpletron simulator.

To compile a source code 'file.basic' written in the SimpleBASIC
programming language into a program 'a.out' in the Simpletron Machine
Language, use the simple(1) compiler as in.
│ simple file.basic

You can use the option ‘-O’ to optimize the compilation, and '-o' to
specify a file other than 'a.out' to compile the program into.


§ TODO

TODO for simpletron(1).
• Extend the Simpletron Simulator's memory to contain 1000 locations to
  enable the Simpletron to handle larger programs.
• Modify the simulator to use hexadecimal values rather than integer
  values to represent simpletron Machine Language instructions.
• Modify the simulator to allow output of a newline.  This requires an
  additional Simpletron Machine Language instruction.
• Modify the simulator to process floating-point values in addition to
  integer values.
• Modify the simulator to handle string input. [Hint: Each Simpletron
  word can be divided into two groups, each holding a two-digit integer.
  Each two-digit integer represents the ASCI decimal equivalent of a
  character.  Add a machine-language instruction that will input a
  string and store it beginning at a specific Simpletron memory
  location.  The first half of the word at that location will be a count
  of the number of characters in the string (i'e', the length of the
  string).  Each succeeding half word contains one ASCII character
  expressed as two decimal digits.  The machine-language instruction
  converts each character into its ASCII equivalent and assigns it to a
  half word.]
• Modify the simulator to handle output of strings stored in the format
  specified above. [Hint: Add a machine-language instruction that prints
  a string beginning at a specified Simpletron memory location.  The
  first half of the word at that location is the length of the string in
  characters.  Each succeeding half word contains one ASCII character
  expressed as two decimal digits.  The machine-language instruction
  checks the length and prints the string by translating each two-digit
  number into its equivalent character.]

TODO for simple(1).
• Allow arrays of integers.
• Allow subroutines specified by the Simple commands {gosub} and
  {return}.  Command {gosub} passes program control to a subroutine and
  command {return} passes control back to the statement after gosub.
  This is similar to a function call in C.  The same subroutine can be
  called from many {gosub} distributed throughout a program.


§ See Also

https://web.archive.org/web/20190819021934/http://www.deitel.com/bookresources/chtp8/CompilerExercises.pdf


§ License

This software is in public domain and is provided AS IS, with NO WARRANTY.