The VisiCalc spreadsheet program, introduced in 1979 to run on the Apple II computer, was considered to be the single most important reason why microcomputers gained acceptance in the business world. Lotus 1-2-3, developed by Mitch Kapor (right), was introduced in 1983  and quickly became the number one selling spreadsheet software on the IBM compatible PC platform. Within a few short years, Lotus 1-2-3 had sold over a million copies of its software package. Many people purchased computers just so that they could run Lotus 1-2-3. 

Lotus was to spreadsheets what Word Perfect was to word processing - both, the number one program in its category, and thus the standard. Just as word processing files are called documents, spreadsheet files are called worksheets. Today, the entire file in Excel is called a workbook, while each sheet is called a worksheet. Other spreadsheet programs include Quattro Pro, Works Spreadsheet, Apple's Numbers, and Google's Sheets.

Spreadsheets contain a grid of rows and columns. Rows (the horizontal part of a worksheet) are numbered from 1 to 65,536 (in Excel 2000) and from 1 to 16,384 (in Works 4.5). Older versions of Lotus 1-2-3 were numbered from 1 to 8192. Actually, the earlier DOS version of Lotus went from 1 to 2048. Columns (the vertical part of a worksheet) are lettered from A to IV. After the column letters go from A, B, C, ... to Z, they use two letters, AA, AB, AC, ... to AZ, then use BA, BB, BC, BD... to BZ, and stop on the 256th column which is lettered IV.

Excel 2013 goes all the way down to row 1,048,576 and out to column XFD!

As in other Windows applications, the F1 key is the help key in Excel.