A spreadsheet consists of cells formed by rows and columns. Additionally, in many spreadsheets you have a third dimension, which you can imagine as various layers laying on top of each other. The third dimension allows you to hide intermediate results, calculate additional results you do not want to appear in the “official” tables, keep information per time period (like 12 layers for each month in a year) while allowing you to make calculations over the entire time interval and much more. Figure 1 shows the three dimensions:

You can think of cells as variables, which value is the value of an associated expression. The expression may be constant, like 1.23, or it may be a function of other cell values. The advantage compared to a programmable calculator is that if you change a number, you directly see all changes in other cells caused by that. Often this allows you to get a feeling how much you may change basic sizes with still getting satisfying results without having to solve the problem analytically.

Spreadsheets offer many editing operations in order to modify, clear, copy and move cells or blocks of cells. Besides the usual mathematical functions, there are functions which work on blocks of cells, like calculating the sum of a block or counting all non-empty elements. Further there are functions working on character strings, because most likely you also want text besides numbers. The next section will introduce you to some of these by examples.

TEAPOT is a traditional spreadsheet and a typical UNIX program, because it does just one thing: Calculations. It does not include any graphics functions and never will, but it allows to export data in many formats, so you can use your favourite graphics software.