# 3.9 Undo/redo

The 'u'ndo command is used to undo or redo write changes done on the file.

    > u?
    Usage: > u 3   ; undo write change at index 3
           > u -3  ; redo write change at index 3
           > u     ; list all write changes

Here's a sample session working with undo writes:

    [0x00000000]> wx 90 90 90 @ 0x100
    [0x00000100]> u                        ; list changes
    00 + 3 00000100: 89 90 c4 => 90 90 90

    [0x00000000]> p8 3 @ 0x100
    90 90 90
    [0x00000000]> u 0
    [0x00000000]> p8 3 @ 0x100
    89 90 c4
    [0x00000000]> u -0
    [0x00000000]> p8 3 @ 0x100
    90 90 90

Note: Read 'undo-seek' for seeking history manipulation.