with a range of 1.67E-307 to 1.67E+308 to 14 significant figure precision but with a much greater processing speed. The manual notes that although source code for the Turbo Pascal's software real data types offering a range of 1E-63 to 1E+63 to 11 significant figures, these were incompatible at a binary level: as well as having a much larger range, the software reals took six bytes in memory and the 8087 ones were eight. Like version 1, version 2 for CP/M-80 only ran on Z80-based CP/M machines. Version 3 Version 3 was released on 17 September 1986. Turbo Pascal 3 supported turtle graphics. In addition to the default software real numbers and 8087 edition of the compiler, Borland also offered a BCD version (TURBOBCD) which offered the same numeric range as real data types but to 18 significant figures. DOS versions Version 4 Released on 20 November 1987, Version 4 was a total rewrite, with both look and feel and internal operation much changed. The compiler generated executables in .EXE format under DOS, rather than the simpler but more restricted .COM executables. The by-then-obsolete CP/M and CP/M-86 operating system versions were dropped when Turbo Pascal was rewritten. Version 4 introduced units, and a full-screen text user interface with pull-down menus; earlier versions had a text-based menu screen and a separate full-screen editor. (Microsoft Windows was still very experimental when the first version was released, and even mice were rare.) An add on package, the Turbo Pascal Graphix Toolbox, was available for Turbo Pascal V4. Version 5.0 Colour displays were replacing monochrome; Turbo Pascal version 5.0, released 24 August 24, 1988, introduced blue as the editor's default background color, used by Borland's DOS compilers until the end of this product line in the mid-1990s. Later versions came in two packages with the same version number: a less expensive "Turbo" package, and a "Borland" package with enhanced capabilities and more add-ons. Version 5.5 This version, released on 2 May 1989, introduced object-oriented programming features for the Pascal language, including concept of classes, static and dynamic objects, constructors and destructors and inheritance, which would become the basis for the Object Pascal found in Borland Delphi. The IDE uses the default blue colour scheme that would also be used on later Borland Turbo products. Other changes to IDE include the addition of a step-by-step debugger to the IDE, and context-sensitive help with description of