are included with the program and can be merged into files as needed. A list solver feature allows variables to be associated with ranges of data or probability distributions, solving for multiple values, which is useful for generating tables and plots and for running Monte Carlo simulations. The premium version now also includes a "Solution Optimizer" for direct setting of bounds and constraints in solving models for minimum, maximum, or specific conditions. TK Solver includes roughly 150 built-in functions: mathematical, trigonometric, Boolean, numerical calculus, matrix operations, database access, and programming functions, including string handling and calls to externally compiled routines. Users may also define three types of functions: declarative rule functions; list functions, for table lookups and other operations involving pairs of lists; and procedure functions, for loops and other procedural operations which may also process or result in arrays (lists of lists). The complete NIST database of thermodynamic and transport properties is included, with built-in functions for accessing it. TK Solver is also the platform for engineering applications marketed by UTS, including Advanced Spring Design, Integrated Gear Software, Interactive Roark’s Formulas, Heat Transfer on TK, and Dynamics and Vibration Analysis. Data display and sharing Tables, plots, comments, and the MathLook notation display tool can be used to enrich TK Solver models. Models can be linked to other components with Microsoft Visual Basic and .NET tools, or they can be web-enabled using the RuleMaster product or linked with Excel spreadsheets using the Excel Toolkit product. There is also a DesignLink option linking TK Solver models with CAD drawings and solid models. In the premium version, standalone models can be shared with others who do not have a TK license, opening them in Excel or the free TK Player. Reception BYTE in 1984 stated that "TK!Solver is superb for solving almost any kind of equation", but that it did not handle matrices, and that a programming language like Fortran or APL was superior for simultaneous solution of linear equations. The magazine concluded that despite limitations, it was a "powerful tool, useful for scientists and engineers. No similar product exists". By version 5.0, TK Solver added Matrix handling functionality. Competitive products appeared by mid-1988: Mathsoft's Mathcad and Borland's Eureka: The Solver. Dan Bricklin, known for VisiCalc and his Software Arts's initial development of TK Solver, was quoted as saying that the market "wasn't as big as we thought it would be because