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HTERM is a "dumb terminal" program which implements hardware flow control and rudimentary handling of UTF-8 encoding and ANSI escapes.

Source Code

Git repo:

Unicode Support

HTERM is primarily designed to interface with Linux systems, either directly connected or through a serial to network bridge. Login consoles on Linux generally use ANSI escapes and UTF-8 encoding.

UTF-8 is a Unicode "encoding." It is a way of representing Unicode characters in an 8-bit byte format. Unicode itself is an abstraction... characters in Unicode have a range of 32-bits, with no defined wire or in-memory structure. UTF-8 is one such format.

The Model T laptops also have a 8-bit character code. For characters in the range 0-127, the ASCII range, the characters are the same in UTF-8. For characters above 127, there is no defined correlation between Unicode and the Model T.

HTERM creates such a correlation. HTERM manages converting between UTF-8, an in-memory Unicode representation, and the Model T's displayable character set.

It turns out that most of the Model 100's character set maps to the 16-bit Unicode range. Given that, and the fact that the Model 100 can deal directly with 16-bit values, HTERM only supports mapping of Unicode characters in the 16-bit range. If it receives a character outside of that range, it will treat it as an unmapped character.