Lotus Improv is a discontinued spreadsheet program from Lotus Development released in 1991 for the NeXTSTEP platform and then for Windows 3.1 in 1993. Development was put on hiatus in 1994 after slow sales on the Windows platform, and officially ended in April 1996 after Lotus was purchased by IBM. Apple Inc.'s Numbers combines a formula and naming system similar to Improv's, but running within a conventional spreadsheet.