Celerity is a powerful application for reading and maintaining C/C++ projects. It can process millions of source code lines. It supports standard C/C++ (and K&R style of sources as well). For each analyzed project, it produces a multifaceted cross-referenced database and shows the source files, include files, source and include files, indexes of lexical elements, includes, include-by's, all macros, macros in a translation unit, all definitions, expandable definitions in a file, expandable definitions in a translation unit, references (function declarations and invocations), reference-by's, contents of per-directory definitions, construct hierarchy, diagnosis outputs, symbol searches, favorites, etc. Definitions and invocations could be expanded conveniently by just a single click. All these combined help a C/C++ developer to quickly read, review, understand, study and maintain a medium or large code base. It has a user-friendly interface with features like tabs, docking, auto-hiding, floating, drag and drop, etc. It allows the user to quickly locate each functional window and rearrange these windows in different layouts. It includes a versatile editor for text/hexadecimal files. Facilitative features include syntax styling, auto-indenting of new lines, auto-completion of words, and auto-formatting of the entire content for better readability. It also dynamically shows cascaded tags in a file. File formats could be defined to specify how to handle directives, colors, styles, etc. FTP files are handled as local files. It includes a studio for multiple projects with commands dealing with each project or all projects. Strong multiple-file find & replace functions enable the user to do quick searches within the background. It has a differencing module which can perform multiple file-to-file or directory-to-directory comparisons in a background manner.