""-
NAME SUE FRED
&&45
JIM
RALPH AVERAGE =
27 25 35 33.00
PERCENT 81.82 63.64 60.00 LOWEST = 45.45 HIGHEST = 81.82
Figure 2. Sample spreadsheet.
define calculated results easily, and individual cells can he changed or edited with no danger of altering the overall structure of the spreadsheet. This means that a VisiCalc file can evolve, as the skills of the programmer improve, or the application changes. VisiCalc also has commands for printing, saving and retrieving the spreadsheet, initializing disks, deleting files, and changing drives. VisiCalc commands to print, change formats, load and save files, etc., consist of a slash (I) followed by one, two, or three single keystroke commands. The allowed commands are displayed at the top of the screen as appropriate. Improper commands are ignored. In other words VisiCalc requires no additional programming skills, other than knowing how to hoot a disk for your system and how to turn on the peripherals. Since VisiCalc is both unique in its command structure and can become quite complex in its logic, it is beyond the scope of a single article to explain everything you will need to master it. However the basic structure of VisiCalc is easily understood, and its power easily demonstrated with a sample spreadsheet. If you need more help to get started, I suggest that you buy any number of soft-covered hooks available. Most of these are less than $20 and I have listed several at the end of this article. Most computer stores will carry anumher of VisiCalc hooks, hut try to buy one that most applies to your system. I have included in Figure 1a short documented spreadsheet program that calculates the class average, and finds the lowest and highest values. To begin, insert and hoot the VisiCalc disk on your microcomputer, and wait for the disk drive to stop before entering the commands in Figure 1. When vou have completed your spreadsheet use the ! key to updat; all 01' the cells. Some features such as averages may need this key. The completed spreadsheet should closely resemble the one shown in Figure 2. Remove VisiCalc and insert a formatted disk in your drive. Save your spreadsheet using the sequence ISS, and use CLASSGRADES as the name for this fde. Once it is saved you can freely experiment and change the version in memory. Move the cursor to cells B6, B8, B10, and B12, and change each student's score. Update all cells with !.Change the value in cell B2, and watch the effect. Use the /IR and IIC commands to insert blank rows and columns in your spreadsheet. Completely erase your spreadsheet using the ICY command. Recover the original file using the ISL sequence. Use the name CLASSGRADES as the name of file to load. If you have a printer on line, try to print your spreadsheet by moving the cursor to cell Al, typing /PP, then moving the cursor to the bottom right cell of the spreadsheet. Use the returnlenter key, and with luck you will retrieve a hard copy of your file. Other features within VisiCalc allow you to view two different "windows" of your spreadsheet simultaneously. I t is -~ even possible to keep some areas "out of hounds," so that careless data entw does not destroy one of the cells. Also since the print command allows you to define the upper left and lower right coordinates to he printed, it is possible to routinely ~
140
Journal of Chemical Education
post your grades, without student names for example, guaranteeing accuracy in the recording of grades, while simultaneously protecting each student's privacy. Practice will he needed before allof the features of VisiCalc will become useful to you, but almost from the start you should he able to create something of value. You may even find creative uses of VisiCalc that you would like to share with others in this column. General References Hergerts, Dovglks "Mastering VisiCale."Syber, Inc.. Berkeley. CA. Crushcow, Jaek,'The VisiCale Book for the IBM Pemonal Cornputor,"Reston Publishing Co., Rerton.VA. B d , Donald H.."The VisiCaleBoakfor the IBMPemonal Coinputer,"R~toto Publishing Co.,Roston, VA.
The Spreadsheet Robert M. Rosenberg Lawrence University. Appleton, WI 54912 E. Virginia Hobbs Brian Hayes, in his first column on Computer Recreations in the October 1983issue of Scientific American, pointed out that the computer spreadsheet programs, such as VisiCalc, designed for financial analysis, can he used to carry out scientific computations and to display mathematical models ( I ) . He described the use of a spreadsheet to generate the Fihonacci series and to represent the Ising model. In this note we describe the application of a spreadsheet to a problem in physical chemistry. A spreadsheet program generates a matrix of cells, arrayed in rows and columns, that appears on the video screen of a computer. If we fill some columns with experimentally determined variahles, cells in additional columns can he filled with any algebraic function of the experimental variahles, and the spreadsheet program automatically calculates the appropriate numerical value for each cell. Thus, a table of experimental and derived values for a scientific problem can he obtained quickly and conveniently without the need to write a specific program. Powers and products of the experimental variahles can he entered in some columns and the columns totalled, so that these sums can be used to determine simple regression equations for the data. Furthermore, a change in one variable or derived quantity results in immediate modification of all subsequent results, so that the spreadsheet is useful for simulation of a mathematical model. The example we use to illustrate the capability of the electronic spreadsheet is the calculatiun of the activity coefficients of lead in amnlgams from measurements of the potentials of cells without liauid . .iunction (2).The experimental data were obtained by Haring et al. (3)and consist i f values of measured voltages and the corresponding mole fractions of lead in one amalgam electrode. The second electrode is of fixed composition for all measurements. For such a cell where the primed variable refers to the electrode of fixed composition. Since a = X y ,
and The first quantity calculated by the spreadsheet is E'. In the limit as X z approaches 0, E' becomes equal to ln(a'd, since yz goes to 1as X p goes to 0. The limiting value of E' was ohtained by fitting values of E' to a sixth-power polynomial function of Xz, using a nonlinear least squares program (4). In an additional column of the spreadsheet,
