1.1. What is ANGEL ?

ANGEL is a software to draw fine graphs from simple input file. This expression is a bit inaccurate. ANGEL does not draw graphs, but only creates EPS (Enhanced PostScript) files from input file. Namely, ANGEL is a translator from Angel language to PostScript language.

♠ PostScript: 1

PS (PostScript) is a programming language optimized for printing graphics and text introduced by Adobe in 1985. In the jargon of the day, it is a page description language. It sounds very difficult but PS has close relation with Macintosh (Mac), since PS firstly appeared in the Apple LaserWriter. However, no one of Mac user knows what PS file is. PS is a good feature in Mac, but it gets into trouble when I give them PS files. They do not know how to print PS files.

♠ PostScript: 2

It is a very nice feature that PS is a programming language written in ascii. By virtue of this, we can read PS file like Fortran program, and understand how PS describes images and text in a device independent manner. If we know the grammar of the PS language, anyone can write PS file directly. Furthermore, PS file can be brought to any machine and can be used on any PS printers without modification like TeX and LaTeX.