7.0;undo *DM*, revision 7.0, 83/08/17 UNDO *DM* -- Undo previous DM command(s). usage: undo FORMAT UNDO UNDO works by compiling a history of DM activities in input and edit pads in reverse chronological order. Invoking UNDO reverses the effect of the most recent DM command. Successive UNDOs will undo further back in history. Note that this only applies to DM operations; Shell operations (such as compiling a program) cannot be undone. The UNDO buffers (one per edit pad and one per input pad) are circular lists that, when full, eliminate the oldest entries to make room for new ones. Entries are grouped together in sets. For example, a S (SUBSTITUTE) command may change 5 lines. While UNDO considers this to be five entries, the five entries are grouped into a single set so that one UNDO will change all five lines back to their original state. When a buffer becomes full, the oldest SET of entries is erased. This means that UNDO will never partially undo an operation: it will either completely undo it or do nothing. An edit undo buffer can hold up to 1024 entries. An input undo buffer can hold up to 128 entries. By default, the <UNDO> key on keyboard 2 invokes the UNDO command. There is no pre-defined key for this function on keyboard 1.