|%||the last result generated|
|%%||the next‐to‐last result|
|%%…% (k times)||the kNull previous result|
|%n||the result on output line Out[n] (to be used with care)|
If you use a text‐based interface to the Wolfram System, then successive input and output lines will always appear in order. However, if you use a notebook interface to the Wolfram System, as discussed in "Notebook Interfaces", then successive input and output lines need not appear in order. You can for example "scroll back" and insert your next calculation wherever you want in the notebook. You should realize that % is always defined to be the last result that the Wolfram Language generated. This may or may not be the result that appears immediately above your present position in the notebook. With a notebook interface, the only way to tell when a particular result was generated is to look at the Out[n] label that it has. Because you can insert and delete anywhere in a notebook, the textual ordering of results in a notebook need have no relation to the order in which the results were generated.