Editing TK Solver (section)

==Core technology==
TK Solver's core technologies are a [[declarative programming]] language, algebraic equation solver,<ref name=TK1.NYT/> an iterative equation solver, and a structured, object-based interface, using a command structure.<ref name=TK1.NYT/><ref>/M for move, /I for insert ...
"carried over from Visicalc."</ref> The interface comprises nine classes of objects that can be shared between and merged into other TK files:
* Rules: equations, formulas, function calls which may include logical conditions
* Variables: a listing of the variables that are used in the rules, along with values (numeric or non-numeric) that have been entered by the user or calculated by the software
* Units: all units conversion factors, in a single location, to allow automatic update of values when units are changed
* Lists: ranges of numeric and non-numeric values which can be associated with a variable or processed directly<ref name=TK1.NYT/> by procedure functions
* Tables: collections of lists displayed together
* Plots: line charts, scatterplots, bar charts, and [[pie chart]]s
* Functions: rule-based, table look-up, and procedural programming components
* Formats: settings for displaying numeric and string values
* Comments: for explanation and documentation

Each class of object is listed and stored on its own worksheet—the Rule Sheet, Variable Sheet, Unit Sheet, etc.  Within each worksheet, each object has properties summarized on subsheets or viewed in a property window. The interface uses toolbars and a hierarchal navigation bar that resembles the directory tree seen on the left side of the [[Windows Explorer]].

The declarative programming structure is embodied in the rules, functions and variables that form the core of a mathematical model.<ref name=ModTools>{{cite book
   |title=Modeling Tools for Environmental Engineers and Scientists
   |url=https://books.google.com/books?isbn=1420003399  |isbn=1420003399
   |author=Nirmala Khandan  |year=2001| publisher=CRC Press }}</ref>