 The version for the TRS-80 Model I had special handling to make it possible to use lowercase letters, even though the hardware itself did not support mixed-case type.Despite its limitations, it was seen at the time as a killer application for the TRS-80 line of machines, along with other breakthrough applications such as VisiCalc.The software market evolved quickly, however, and its popularity soon gave way to WordPerfect running on the IBM PC.