TeXShop is a very useful tool, a TeX previewer for Mac OS X, written in Cocoa.Since pdf is a native file format on OS X, TeXShop uses \"pdftex\" and \"pdflatex\" rather than \"tex\" and \"latex\" to typeset; these programs in the standard teTeX distribution of TeX produce pdf output instead of dvi output. TeX is a typesetting program by Donald Knuth, used extensively in mathematics, computer science, physics, economics, and other fields. For a history of the development of TeX, see Just What Is TeX. Consult the TeX Users Group Web Site for additional information.To use TeXShop, you need to learn TeX or LaTeX.What\'s New in This Release: [ read full changelog ]· Line numbers are displayed in the source file.· A preference item turns this feature on or off; a menu item turns it on or off for the currently active window.· This feature depends on free code by Paul Kim at Noodlesoft.· The code is at http://www.noodlesoft.com/blog/; see \"Displaying Line Numbers with NSTextView\".· I don\'t read this blog, but the code was pointed out to me in an email from Ryan Cuthbertson, who downloaded the TeXShop source code, implemented the change, and sent crystal clear instructions explaining how to add the feature. Kudos to Cuthbertson. Kudos especially to Paul Kim and Noodlesoft; Kim\'s code is so well written that Cuthbertson had to add only 32 lines of code to TeXShop to make it work.· TeXShop now uses Sparkle to implement \"Check for Updates.\"· This brings many advantages. Rather than directing a user to the TeXShop web page when an update is available, TeXShop now lists new features directly, downloads the update upon request, and even quits TeXShop, installs the new version, and restarts the program upon request.· Sparkle is another remarkable product from the open source software community.· Written by Andy Matuschak and available at http://sparkle.andymatuschak.org/, it provides every feature you\'d want in an update mechanism.· The documentation for developers available on the web page is a model of clarity and simplicity. Sparkle is used by a number of other GUI programs for TeX, so users for find it familiar.· The console window has been greatly improved by Will Robertson, who sent a new Nib file containing his changes several months ago. I waited to implement the improvements until I could add a console preference tab to TeXShop Preferences allowing users to modify Robertson\'s choices. The font and background color for the console can be modified in Preferences. Users can adjust the console width to match the number of characters typically output by TeX, and then select a preference allowing the window to be resized only in the vertical direction. Note that preference changes are immediately reflected in the console, so the trick to easy console configuration is to bring a console window to the front, open Preferences, try out various fonts, font sizes, and background colors until satisfied, activate horizontal resizing and adjust the console width, and then, if desired, lock down this width in Preferences.· A number of items in the Preference panel have been moved to make the operation of the panel more transparent. The most important tab items come first: Source, Preview, Console, Typesetting. In the Preview tab, the \"Fixed Magnification Amount\" appears immediately following the \"Magnification Method\" to make it clearer that \"Fixed Magnification\" only applies when the \"Magnification Method\" is \"Fixed Magnification.\"· Previously, clicking the green \"Zoom Dot\" on TeXShop windows expanded the window to fill the screen. An attempt has been to made this operation more rational. The Source window now expands to fill the left portion of the screen; the console expands only vertically, and the Preview window expands to fill the right portion of the screen. The Preview window expands by the largest amount because users may want to zoom the image and check fine details. I\'d appreciate advice on refinement of the zoom behavior. Recall that the behavior must make sense on small portable screens and large Cinema displays.· For some time, TeXShop recognized hidden preference items to set the background color of the Source and Preview windows. These preference items are now exposed and can be set in the Preference dialog.· A bug in the MatrixPanel code disabled the hidden preference \"matrixsize\'\'. This bug is fixed.· The name of the alternate typesetting mode \"TeX and Ghostscript\" has been changed to \"TeX and DVI\". This fulfills a request of the American Mathematical Society, who have been dealing with users claiming that TeXShop cannot produce dvi files.