Buffer Overflow

This series explores the phenomenon of buffer overflow. To control vintage plotters, we use the classic rs232 serial interface, sending HPGL commands to the device. These plotters, like the HP 7475A featured in this series, have a small memory capacity of e.g. 1024 bytes. It's the user's job to prevent the machine's internal buffer from being overloaded by sending too much data at once. This can be managed through either hardware or software handshakes.

In the creation of these pieces, we intentionally skip the handshake process. This ensures that buffer overflows will occur, but it's unpredictable exactly when they will happen, making it impossible to recreate the same overflow twice.

The consequence of a buffer overflow is that the plotter's interpreter misses some commands, which might lead to, for example, drawing lines without having selected a pen. Other times, unexpected diagonal lines appear if the plotter's firmware goes into an error state.


About HP-GL (from the HP7475A manual)
HP-GL (Hewlett-Packard Graphics Language) is the graphics programming language that is actually sent to and understood by the plotter. HP-GL instructions consist of two-letter mnemonics that are usually followed by numeric parameters. With the exception of certain escape sequence instructions which are used for control of interface functions in an RS-232-C environment, all data received by the plotter is interpreted as HP-GL instructions. You can include HP-GL instructions directly in the computer language output statements, or you can use AGL statements which the computer encodes and sends to the plotter as HP-GL instructions.

An excerpt from the HP 7475A's manual about the handhshaking options

These are some test-files that were the base for the drawings of this series. These are calibration tests to get an idea of the ink-flow at certain speeds of moving the pen over paper.

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Work in progress, plotted on a vintage HP 7475A plotter using rotring archival ink

buffer overflow 🔴
black archival ink
297x420mm/11.69x16.53in (a3)
hicetnunc/35298

buffer overflow
black archival ink
297x420mm/11.69x16.53in (a3)

buffer overflow 🔴
original 80's felt tip pens on paper
297x420mm/11.69x16.53in (a3)

buffer overflow
black archival ink
297x420mm/11.69x16.53in (a3)

buffer overflow
original 80's felt tip pens on paper
297x420mm/11.69x16.53in (a3)

buffer overflow 🔴
original 80's felt tip pens on paper
297x420mm/11.69x16.53in (a3)
hicetnunc/1083

buffer overflow
original 80's felt tip pens on paper
297x420mm/11.69x16.53in (a3)

buffer overflow 🔴
original 80's felt tip pens on paper
297x420mm/11.69x16.53in (a3)
hicetnunc/577554