 Purchases were often instigated by middle managers and senior staff who saw the potential – once the revolutionary VisiCalc spreadsheet, the killer app, had been surpassed by a far more powerful and stable product, Lotus 1-2-3.IBM's dominance of the mainframe market in Europe and the US encouraged existing customers to buy the PC, and vice versa; as sales of what had been an experiment in a new market became a substantial part of IBM's financials, the company found that customers also bought larger IBM computers.Unlike the BUNCH and other rivals IBM quickly adjusted to the retail market, with its own sales force competing with outside retailers for the first time.