When the editor displays existing data, each line consists of a 6-column line command field followed by a 72-column data field. The line command fields contain the first 6 digits of the sequence numbers in the data. If the data has no sequence numbers, the line command fields contain relative numbers that start at 1 and are incremented by 1.

Based on your action, the ISPF editor places the cursor in the most useful position. To help you find the cursor, the editor intensifies the line command field that contains the cursor.

If the data contains characters that cannot be displayed, blanks replace those characters on the panel but not in the data. You cannot type over the blanks. You can display and edit undisplayable characters by entering hexadecimal mode or by using the FIND and CHANGE commands with hexadecimal strings. See HEX—Display Hexadecimal Characters for information on entering hexadecimal mode.

Printer control characters, if present, are displayed and are treated as part of the data. ASA control characters are alphanumeric and you can edit them. Machine control characters, however, cannot be displayed and are replaced on the panel with blanks.

When you are editing existing data, the selected member or sequential data set is read into virtual storage, where it is updated during edit operations. Use of virtual storage for editing work space results in high performance, but might require a large user region. If you use all available storage, an ABEND occurs, and you lose the work space unless recovery mode is on.