TPU begins with the screen divided into two areas by a highlighted status bar. When you start TPU, it looks for a file with the filename you give it. If the file is there, the latest version of it is read into the upper window. If the file is not found, a message appears in the lower window, and the End of Text line appears in the upper window. You can move around in the file by using the arrow keys.
Most files are longer than one screenful of text.
If you want to see the beginning, use the arrow keys to move to the top of the file. As you move up, the last part of the text will scroll off the bottom of the screen. It invokes the TPU command line. The command line will show up beneath the highlighted status bar. When you type Quit, it will exit the editor without saving any changes.