PCjs Device Classes

In the spirit of Vanilla JS, a very simple set of ES2015 (ES6) JavaScript classes are used to create a variety of newer (late 2017) PCjs Machines:

which, in turn, build on a simple set of library classes:

Examples of those newer PCjs Machines include:

On the PCjs website, Jekyll Front Matter and templates are used define and embed complete machines. The Markdown file in the TI-57 directory provides a good example. The Front Matter at the top of the file is where you define one or more machines, each with the following minimum set of properties:

  - id: ti57
    type: ti57
    name: TI-57 Programmable Calculator
    config: /devices/ti57/machine/rev0/ti57.json

The config property specifies the location of a JSON configuration file that describes the machine’s internal devices, the IDs of any visual controls that they bind to, and any resources they require (e.g., ROM contents).

Alternatively, a JSON configuration blob can be embedded directly in the machine definition:

    config: |
        "ti57": {
          "class": "Machine",
          "type": "TI57",
          "name": "TI-57 Emulator",
          "bindings": {
            "clear": "clearTI57",
            "print": "printTI57"
        "chip": {
          "class": "Chip",
          "type": "TMS-1500"
        "clock": {
          "class": "Time",
          "cyclesPerSecond": 650000,
          "bindings": {
            "run": "runTI57",
            "speed": "speedTI57",
            "step": "stepTI57"
        "display": {
          "class": "LED",
          "type": 3,
          "cols": 12,
          "rows": 1,
          "color": "red",
          "backgroundColor": "black",
          "bindings": {
            "container": "displayTI57"
        "input": {
          "class": "Input",
          "location": [139, 325, 368, 478, 0.34, 0.5, 640, 853, 418, 180, 75, 36],
          "map": [
            ["2nd",  "inv",  "lnx",  "\\b",  "clr"],
            ["lrn",  "xchg", "sq",   "sqrt", "rcp"],
            ["sst",  "sto",  "rcl",  "sum",  "exp"],
            ["bst",  "ee",   "(",    ")",    "/"],
            ["gto",  "7",    "8",    "9",    "*"],
            ["sbr",  "4",    "5",    "6",    "-"],
            ["rst",  "1",    "2",    "3",    "+"],
            ["r/s",  "0",    ".",    "+/-",  "=|\\r"]
          "bindings": {
            "surface": "imageTI57",
            "power": "powerTI57",
            "reset": "resetTI57"
        "rom": {
          "class": "ROM",
          "wordSize": 13,
          "valueSize": 16,
          "valueTotal": 2048,
          "littleEndian": true,
          "file": "ti57le.bin",
          "reference": "",
          "values": [

Front Matter also provides a convenient way to define styles for any of the visual controls. The syntax is similar to basic CSS, except that identifiers with a leading underscore correspond to control IDs without the underscore (in CSS, you would use # in front of each identifier, but that’s a comment character in Front Matter). You can also define style classes, by using identifiers with a leading period.

    position: relative;
    display: inline-block;
    position: absolute;
    left: 16%;
    top: 7%;
    width: 70%;
    height: 4%;

Next, add some HTML markup at the desired page location, such as:

<div id="ti57">
  <img id="imageTI57" src="/devices/ti57/images/ti57.png"/>
  <div id="displayTI57"></div>
  <button id="powerTI57">Power</button>
<div style="float:left;">
  <div style="width:100%;">
    <textarea id="printTI57" cols="78" rows="16"></textarea>
  <button id="runTI57">Run</button>
  <button id="stepTI57">Step</button><span id="speedTI57">Stopped</span>
  <button id="resetTI57">Reset</button>
  <button id="clearTI57">Clear</button>

Finally, you embed the machine with a simple include template:

which automatically adds all the necessary scripts, as listed in machines.json:

<script src="/modules/devices/lib/stdio.js"></script>
<script src="/modules/devices/device.js"></script>
<script src="/modules/devices/input.js"></script>
<script src="/modules/devices/led.js"></script>
<script src="/modules/devices/rom.js"></script>
<script src="/modules/devices/time.js"></script>
<script src="/modules/devices/tms1500.js"></script>
<script src="/modules/devices/machine.js"></script>

and then creates the machine with:

new Machine('ti57','{JSON blob}');

or, if an external JSON file is used, with:

new Machine('ti57','/devices/ti57/machine/rev0/ti57.json');

Of course, you can add any or all of those lines yourself if you don’t want to use the include template.