In its first versions, the CDR file format was a completely proprietary file format primarily used for vector graphic drawings and developed by Corel Corporation, recognizable by the first two bytes of the file being "WL". Starting with Corel Draw 3, the file format changed to a Resource Interchange File Format (RIFF) envelope, recognizable by the first four bytes of the file being "RIFF", and a "CDR*vrsn" in bytes 9 to 15, with the asterisk "*" being in early versions just a blank, and beginning with Corel Draw 4, the version number of the writing program in hexadecimal ("4" meaning version 4, "D" meaning version 14). The actual data chunk of the RIFF remains a Corel proprietary format.
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.