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Mike Daley edited this page Sep 10, 2026 · 2 revisions

Printers

The emulator includes four virtual dot-matrix printers, rendered onto simulated fanfold paper. Anything an Apple II could print -- a BASIC listing, a ProDOS catalog, an AppleWorks document, banner software -- produces a page you can read, save or print for real.

Open View > Printer... for the printer and its paper, and View > Print Browser... to review past output.

Table of Contents

Supported Printers

Printer Interface Notes
Epson FX-80 Parallel Card The de-facto standard dot-matrix printer; ESC/P command set
Apple DMP Parallel Card Apple's Dot Matrix Printer
ImageWriter I Super Serial Card Apple's serial dot-matrix printer
ImageWriter II Super Serial Card Adds draft, standard and NLQ print qualities

Each printer emulates its own character ROM, so the glyph shapes, character spacing and print quality modes are those of the machine being imitated rather than a generic font. The ImageWriter II, for instance, carries separate ROMs for draft, standard and near-letter-quality output in both fixed and proportional spacing.

Connecting a Printer

A printer needs the right interface card installed:

  • Epson FX-80 and Apple DMP need a Parallel Card in slot 1 or 2.
  • ImageWriter I and ImageWriter II need a Super Serial Card in slot 1 or 2.

Install the card from View > Expansion Slots (see Expansion-Slots), then choose the printer model in the Printer window.

Printer sounds can be toggled independently; they are wired to the same main volume control as the speaker and drives.

Printing from the Apple

Printing works exactly as on real hardware -- redirect output to the slot holding the interface card:

PR#1            REM send output to slot 1
CATALOG         REM this now goes to the printer
PR#0            REM back to the screen

From Applesoft you can also PRINT CHR$(4);"PR#1" inside a program. Software with its own printer setup (AppleWorks, Print Shop) should be pointed at whichever slot holds the card.

The Print Browser

The Print Browser collects completed pages so you can go back through a session's output. Pages can be saved as images, and the paper rendering is what gets exported -- what you see is what you get.

Editing the Printer Fonts

The glyph banks the models render from can be authored in a standalone editor at /printers/rom-editor.html.

  • Draws characters dot by dot on the model's own glyph grid.
  • Handles the alternate-language code points each printer swapped in per locale.
  • Imports and exports either as a ROM module or as ASCII dot art.
  • Traces over a scan of a manual's character chart, so a font can be rebuilt from the page it was printed on.

It is one plain page with no build step and no imports, so it opens straight off disk as readily as from the emulator. The printer ROM modules in the source tree remain the authority — the editor's built-in defaults are generated from them, and a check in npm run check fails if the two drift apart.

How It Works

The interface card receives bytes from the Apple exactly as the real hardware would: the Parallel Card takes Centronics-style strobed bytes, and the Super Serial Card runs them through an emulated ACIA 6551, so baud rate and framing behave as they should.

Those bytes reach a printer emulation in src/js/printer/, which interprets the control codes of the selected model -- ESC/P for the Epson, Apple's own escape sequences for the DMP and ImageWriters -- and rasterises the result through the printer's character ROM onto the paper canvas.

Because the printer is driven by the byte stream rather than by intercepting BASIC, anything that talks to the card prints correctly, including software that does its own graphics by sending column-addressed bit patterns.

The printer emulation is covered by characterization tests in tests/js/, which capture the event stream from PrinterBase.setEventSink() -- so a change in how a control code is interpreted shows up as a test diff rather than as a subtly wrong page.

See Also

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