The list of edit descriptors is scanned from left to right (apart from the effect of parentheses) starting at the beginning of the list whenever a new data transfer statement is executed. The action of the I/O system depends jointly on the next edit descriptor and the next item in data-transfer list. If a data descriptor comes next then the next data item is transferred if one exists, otherwise the format scan comes to an end. If a colon descriptor (:) comes next and the data-transfer list is empty the format scan ends, otherwise the descriptor has no effect. If any other control descriptor comes next then it is obeyed whether or not the data-transfer list is empty.
If the format list is exhausted when there are still more items in the data-transfer list then forced reversion occurs: the file is positioned at the beginning of the next record and the format list is scanned again, starting at the left-parenthesis matching the last preceding right-parenthesis. If this is preceded by a repeat-count then this count is re-used. If there is no preceding right-parenthesis then the whole format is re-used. Forced reversion has no effect upon the settings for scale-factor, sign, or blank control. Forced reversion can be useful when reading or writing an array contained on a sequence of records since it is not necessary to know how many records there are in total, but when producing printed output it is easy to forget that a carriage-control character is required for each record, even those produced by forced reversion.