the running of this macro language involves expansion and execution stages which do not interact directly. Expansion includes both literal expansion of macro definitions as well as conditional branching, and execution involves such tasks as setting variables/registers and the actual typesetting process of adding glyphs to boxes. The definition of a macro not only includes a list of commands but also the syntax of the call. It differs with most widely used lexical preprocessors like M4, in that the body of a macro gets tokenized at definition time. The TeX macro language has been used to write larger document production systems, most notably including LaTeX and ConTeXt. Development The original source code for the current TeX software is written in WEB, a mixture of documentation written in TeX and a Pascal subset in order to ensure readability and portability. For example, TeX does all of its dynamic allocation itself from fixed-size arrays and uses only fixed-point arithmetic for its internal calculations. As a result, TeX has been ported to almost all operating systems, usually by using the web2c program to convert the source code into C instead of directly compiling the Pascal code. Knuth has kept a very detailed log of all the bugs he has corrected and changes he has made in the program since 1982; , the list contains 440 entries, not including the version modification that should be done after his death as the final change in TeX. Knuth offers monetary awards to people who find and report a bug in TeX. The award per bug started at US$2.56 (one "hexadecimal dollar") and doubled every year until it was frozen at its current value of $327.68. Knuth has lost relatively little money as there have been very few bugs claimed. In addition, recipients have been known to frame their cheque as proof that they found a bug in TeX rather than cashing it. Due to scammers finding scanned copies of his checks on the internet and using them to try to drain his bank account, Knuth no longer sends out real checks, but those who submit bug reports can get credit at The Bank of San Serriffe instead. Distributions and extensions TeX is usually provided in the form of an easy-to-install bundle of TeX itself along with Metafont and all the necessary fonts, documents formats, and utilities needed to use the typesetting system. On UNIX-compatible systems, including