Developed in 1982 by Adobe Systems, the .ps extension is a file type used by the publishing industry. Prior to the development of PostScript, it was not possible to print images and text on the same page. Postscript addressed this by defining a language that allowed applications to instruct the printer how to display objects on the page. This file type revolutionised publishing allowing certain curved items to be printed that previously could only be printed on specialist CAD printers. Although no longer as popular or common as it was historically, it is still an important file type.
PostScript is actually a programming language as well as a file type. Typically files are created by applications such as Adobe Acrobat or Quark Xpress. Now a legacy file format, most printers and programs continue to support this format, with the only pre-requisite being a printer utility that supports PostScript. The file basically contains a set of instructions that tell the printer what to print and provide the co-ordinates on the page of where an object or text should be printed.
JPG's are often used for web sites and email as they are generally smaller file sizes as they are lossy meaning that some image quality is lost when the JPG is compressed and saved. The resultant 'lossy' file means that quality can never be recovered. The JPG format is often used in digital camera memory cards. The JPG file is a great format as it often manages to compress files to 1/10 of the size of the original file which is especially good for saving on bandwidth.
JPG is a graphical file format for editing still images, it offers a symmetrical compression technique which is processor intensive and time consiming in both compression and decompression. JPEG is a joint standard of the International Telecommunications Union (ITU-T T.81) and the International Organization for Standardization (ISO 10918-1). JPEG involves a lossy compression mechanism using discrete cosine transform (DCT). Compression rates of 100:1 can be achieved, although the loss is noticeable at that level. Compression rates of 10:1 or 20:1 yield little degradation in image quality.
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