Updated version of Comp – Simple 4-bit/1 Hz virtual computer for learning purposes

• Processor has one 8 bit register.
• Ram is separated in two address spaces; one for instructions, called CODE, and another for data, called DATA.
• All instructions are 8 bits long.
• Execution starts at the first address (0) of the CODE ram.
• Execution stops when program reaches the last address (15) of the CODE ram.
• Most of instructions consist of instruction code and address:

instruction code - 4 bits
  |  +-- address - 4 bits
  v  v
----***-  ->  READ 14  ->  Copy value stored at address 14 of DATA ram to register.

• All addresses specified by instructions refer to DATA ram, except for addresses of Execution Control instructions (JUMP, IF MAX, IF MIN, ...). They refer to CODE part of ram.
• Some instructions (JRI~<>&V) do not specify address. They operate on register (SHIFT L/R, NOT, ...) or between register and predefined DATA address (AND, OR, ...).
• Whatever gets written to the last address is sent to the printer, or to stdout if program is running in a non-interactive mode.
• When reading from the last address (15), we get a random byte value, or a single word from stdin, if program is running in non-interactive mode.
• In this word every * is interpreted as true and all other characters as false. If word starts with a digit, it is then read as a number and converted appropriately.
• Program will start in a non-interactive mode when any input is piped in, or any option is given. For instance echo | ./comp <file>
• Programs can be saved with s key and loaded by passing their name as a parameter.
• If more than one filename is passed, the computers will be chained together (stdin > comp-1 > comp-2 > ... > stdout).
• If folder is passed, all files in that folder that have suffix .cm2 will be loaded in an alphabetical order.

Most of the instructions, together with the highlighted word that they use/modify, are pretty self-explainatory. Exception are instructions that start with -***, and are a part of JRI~<>&VX instruction cluster. They are:

• J – JUMP_REG,
• R – READ_REG,
• I – INIT,
• ~ – NOT,
• < – SHIFT_L,
• > – SHIFT_R,
• & – AND,
• V – OR,
• X – XOR.

(Use Shift–Left/Right Arrow to easily shift between them.)
Detailed descriptions of all instructions can be found HERE.

• Space – Flip bit,
• Tab – Switch address space,
• Enter – Start/pause execution,
• Esc – Cancel execution,
• Delete, Backspace – Delete word or move following words up if empty,
• Insert, ] – Insert empty word and move following words down,
• s – Save ram to textfile named punchcard-<num>.cm2. To load it, start program with ./comp <file>,
• q – Save and quit.

Detailed descriptions of all keys can be found HERE.

• --non-interactive, -n – Run program in a non-interactive mode (not necessary if any other option is present, or if input is piped).
• --char-output, -c – Convert words to characters when printing to stdout.
• --filter, -f – Convert characters to words when reading from stdin, and words to characters when printing to stdout.
• --game, -g – Same as filter, but read characters directly from keyboard.
• parse – Convert program to c++ code (other options may be specified).
• compile – Compile program (other options may be specified).

• Install Tiny Core Linux on VirtualBox using this instructions.
• Run the UNIX commands.

Make and g++ need to be installed first. On Ubuntu and Debian you can get them by running sudo apt-get install build-essential, on OS X they get installed automatically after running make.

$ git clone https://github.com/gto76/comp-m2.git
$ cd comp-m2
$ ./run

$ docker run -it --rm mvitaly/comp-m2 <options>

$ ./comp -n examples/fibonacci.cm2
-------*   1
-------*   1
------*-   2
------**   3
-----*-*   5
----*---   8
...

$ echo "3 4" | ./comp examples/multiply.cm2
----**--  12

$ ./comp -c examples/hello-world.cm2
Hello world

$ echo "Hello world" | ./comp -f examples/to-upper-case.cm2
HELLO WORLD

$ ./comp compile -g examples/cat-and-mouse/
Compiled as cat-and-mouse
$ ./cat-and-mouse

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