TK's worksheet structure has been carried over from its DOS predecessor. Old or new users will become easily accustomed to the various sheets for rules (or equations), variables, tables, lists, functions, plots, formats, and units.

At the very minimum, you will be using the rule and variable sheets. The method is very simple, just type the equations in the rule sheet as you have them on paper. The participating variables are automatically included in the variable sheet, which is the heart of TK. As you begin to enter numbers for some of the variables, TK figures the remaining variables by backsolving your equations. Any variable can be an input or output without having to rearrange your equations. The equations can even be complex arithmetic expressions that include logical and Boolean statements. TK will prompt for under-defined and over-defined models, and point to inconsistent rules.

From the rule sheet you can also call built-in or user-defined functions to perform a task similar to a subroutine. Your models will be more complete if you take advantage of TK's unit feature embedded in the variable sheet. Not only can you select the basic system of units your model will be consistently dimensioned to, but you can also change the displayed units to any other system you choose. Once you change the unit of any variable, TK automatically updates the numbers so unit consistency is maintained.

Using a version of the Newton-Raphson iteration technique, TK can solve sets of equations with an equal number of unknowns. Starting with a few guess values, TK will iterate through for the rest of the variables. Unlike in a spreadsheet where you copy the same formula for every row of ranges-of-input values you want calculated, TK uses a single rule over the range of any variables. When you simply declare those variables as an input and output, TK can create lists or arrays on-the-fly.

But the easiest way to create lists and plots is with the new Wizard tools. Starting from the List Wizard, TK will use your model's variables as a list that can be filled in a number of ways. In turn, these lists can be combined in tables simply by including the name of the variable/list as part of the table.

The lists can also be plotted using the new Plot Wizard. Although the basic plots can still be done with TK's limited tools, the Plot Wizard adds several options for types of plots in 2 and 3 dimensions, as well as in plot control for attributes.

The presentation capabilities of TK are in the Mathlook. It will accept any equation from your models and display it in true math notation along with comments and graphics. In this context, you can use Mathlook as a formula checker and as a medium to paste its contents into other Windows applications.

Access to your Windows word processor, spreadsheet, or database is through the object linking and embedding (OLE) feature where TK works as a server application. When a TK model and its graphics are linked to or embedded into your word processor or spreadsheet, any changes are reflected in all the linked documents.

Thanks to Visual Basic, you can now build front-end interfaces to TK without accessing it directly, yet still take advantage of its powerful backsolving engine and ease of use. TK can also access programs like VISIO where it can control the attributes of any shape. A developer's kit is available for this OLE automation.

For users who still rely on legacy code in FORTRAN or C, TK's 3.0 version supports external function calls to this code without having to rewrite a single line of it. Although not the easiest task, you can pass arguments to your subroutines to or from your TK models and still be able to make these subroutines backsolvable through TK.

New additions in this version of TK make it more powerful and easier to use than ever. TK's ability to communicate with mainstream GUI tools in the Windows environment combined with its powerful math engine marks this version's entrance into the flexible system development league.