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the same but obliqued
BX definition must follow TX so BX can use TX
LX definition must follow TX so LX can use TX
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virtex - virgin TeX for production typesetting virtex is a version of the \*(TX program that has no preloaded macro packages, but is capable of loading a special preformatted binary file, called a format ( .fmt ) file produced by the initex (1) program.

Preprocessing of large macro files and font definitions by initex makes it possible to rapidly load complex packages, like plain \*(TX, \*(AX, \*(AY, or \*(LX, without the overhead of macro parsing and file opening that would otherwise be experienced.

virtex can be invoked directly, providing it with a name of a format file specially prefixed by an ampersand:

This causes it to load the binary file named plain.fmt from a directory in the standard TEXINPUTS search path, and then load the text file filename and process it. The quotes are needed to protect the ampersand from Unix shell interpretation.

Because this need occurs frequently, Unix virtex provides a convenient shorthand. If it is invoked under a name other than virtex , such as footex , it will behave as if it had been invoked as "virtex '&footex'" and first load a file named footex.fmt . Thus, amslatex , amstex , lamstex , latex , slitex , tex , texinfo , and others can all be file system links to virtex , without requiring additional disk space. =====================================================================

initex (1), tex (1).