How Does a Graphing Calculator Work?

By Ezmeralda Lee


A graphing calculator is necessary for many different kinds of math. Not only does it do math much faster than almost any person, but it is also capable of performing mathematical functions that no person can calculate because the numbers are too large or small. A graphing calculator is especially useful for geometric equations and plotting lines. All the user has to do is plug in the right coordinates, and the calculator draws the lines. There are several different parts of a graphing calculator, and each one is necessary for the function of the whole.


A graphing calculator uses all of the same functions as a normal calculator. All of the basic math formulas and calculations are programmed into the calculator so that the answers can be found. Multiplication, subtraction, addition, division, logarithms, fractions, decimals, square roots and all other math functions can be preformed by the graphing calculator. When a problem is typed into the calculator, the pre-programmed results and functions give the user the correct answer.

The Bbrain

The computer inside a graphing calculator is fairly complicated. Not only does the calculator have to be programmed to solve algebra and geometry equations, it also has to be programmed to draw the solutions on a graph. The calculator is given formulas to carry out when a user types in graphing commands. Some of the most common functions are matrixes, logarithms and plotting lines. If the user types in a command such as "-10,10," then the calculator is programmed to give the correlating solution. Many graphing calculators use the Zilog Z80 CPU system, which is a small microprocessor.

Graphing Capabilities

Usually the graphing capabilities of a graphing calculator are somewhat limited. The results of any equation (such as "-10,10") are divided between how many pixels are in the screen. For a 127-pixel screen, the graph is divided into 127 dots that arc across the screen according to the graph specifications. Sometimes the dots do not get connected, so it is necessary to connect them manually when re-recording the graph results on a piece of paper. Unless the user knows how to input the graph coordinates, the resulting graph will be no where near the correct answer. The graphing calculator inputs the literal commands that are entered, which can be way off from the desired result.

Graphing Calculator Flaws

The flaws of the graphing calculator are somewhat minor, but can cause serious problems. As mentioned above, in many cases the resulting graphs are not complete due to screen issues. This can be a serious problem for a user who does not know what the graph should look like. Another flaw is the fact that each calculator has specific ways that graphing equations need to be entered. A slight deviation from the required formula can cause incredibly different results. Another problem with graphing calculators is that certain shapes cannot be completed.