Adobe Illustrator Artwork (AI) is a proprietary file format developed by Adobe Systems for representing single-page vector-based drawings in either the EPS or PDF formats. The .ai filename extension is used by Adobe Illustrator. The AI file format was originally a native format called PGF. PDF compatibility is achieved by embedding a complete copy of the PGF data within the saved PDF format file. This format is not related to .pgf using the same name Progressive Graphics Format. The same “dual path” approach as for PGF is used when saving EPS-compatible files in recent versions of Illustrator. Early versions of the AI file format are true EPS files with a restricted, compact syntax, with additional semantics represented by Illustrator-specific DSC comments that conform to DSC's Open Structuring Conventions.
PCX, standing for Personal Computer Exchange, is an image file format developed by the now-defunct ZSoft Corporation of Marietta, Georgia. It was the native file format for PC Paintbrush and became one of the first widely accepted DOS imaging standards, although it has since been succeeded by more sophisticated image formats, such as BMP, JPEG, and PNG. PCX files commonly stored palette-indexed images ranging from 2 or 4 colors to 16 and 256 colors, although the format has been extended to record true-color (24-bit) images as well. PCX was designed during the early development of PC display hardware and most of the formats it supported are no longer used, Table A shows a list of the most commonly used PCX formats. Contemporary image editing programs may not read PCX files that match older hardware.