pdf The .pdf file format extension was developed by Adobe systems in 1993 as a means of presenting documents in a consistent manner across different platforms, hardware, operating systems, and applications. The format was not released as an open source document format until 2008, though minimal proprietary technologies still controlled by Adobe Systems exist in the format. Every .pdf document carries with it the necessary meta information required to properly reconstruct the text, fonts, and graphics used to produce the document. This ensures that documents will be viewed in exactly the same way the author intended regardless of the device used to open the document. From conception to date, Adobe Systems has continued to support the format adding features with every iteration of the standard including hardened algorithms for document encryption and privacy. Today, many freely available readers exist allowing you to open and view .pdf documents and create or convert other file formats such as .jpeg and .doc into .pdf documents.
tcr The .tcr filename extension is a compressed text file format for eBooks and text associated with eBook reader software developed by Psion, a London based techonology company. The format has its beginnings in the early 90's and was designed for use on the PDAs released by the company, particularly the Series 3 handheld PDA. Though the format is proprietary and was intended for exclusive use on Psion devices, today, a few eBook reader applications can open files encoded in this format. As PDAs eventually lost there popularity, the format was discontinued when Psion eventually pulled out of the PDA market.