Frankston described VisiCalc as a "magic sheet of paper that can perform calculations and recalculations", which "allows the user to just solve the problem using familiar tools and concepts". The Personal Software company began selling VisiCalc in mid-1979 for under $100, after a demonstration at the fourth West Coast Computer Faire and an official launch on June 4 at the National Computer Conference. It required an Apple II with 32K of random-access memory (RAM), and supported saving files to magnetic tape cassette or to the Apple Disk II floppy disk system.