Bidi terminal semantics

From: Markus Kuhn (
Date: Wed Sep 15 1999 - 10:22:05 EDT

I just discovered

  ECMA Technical Report TR/53
  Handling of bi-directional Texts

which provides a nice short tutorial with examples on how to implement
the ECMA-48 bidi terminal emulation. The curious thing is that is also
describes a mode in which received characters have an implicit
directionality, very much like the Unicode bidi algorithm. But unlike
the Unicode bidi algorithm, ECMA TR/53 does not just discuss a flat
character stream, but also interactive editing, tabulation, and many
other things of concern to the developer of a VT100-style terminal

It will now be interesting to see, how compatible the
ECMA TR/53 implicit directionality mode is with the Unicode
bidi algorithm, and whether it is possible to implement
a terminal emulator that follows both specifications.



Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>

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