By the mid-1980s the rapid improvement in microcomputers, and especially the introduction of the graphical user interface and data-rich application programs like Lotus 1-2-3 led to an increasing interest in using personal computers as the client-side platform of choice in client–server computing. Under this model, large mainframes and minicomputers would be used primarily to serve up data over local area networks to microcomputers that would interpret, display and manipulate that data. For this model to work, a data access standard was a requirement – in the mainframe field it was highly likely that all of the computers in a shop were from one vendor and clients were computer terminals talking directly to them, but in the micro field there was no such standardization and any client might access any server using any networking system.