5250 error 0018: Key used to exit field not valid

What it means

Normally, when you type the last character of a 5250 field, the cursor jumps to the next input field on its own. A programmer can switch that off for a field with CHECK(FE) in the DDS, or with CHGINPDFT(FE). The field is then field exit required. After you type its last character, the cursor stays under that character until you press a field exit key. IBM's DDS reference counts Field Exit, Field+, Field- and the cursor movement keys as field exit keys. Any other key at that point is an error, and the display station shows 0018.

So 0018 mostly happens to quick typists. They fill a field, assume the cursor has moved on, and start the next value. The first character of the next value is refused.

Programmers use this check to stop data spilling between fields. In a field without it, one character too many lands quietly in the next field and both values end up wrong. With CHECK(FE), the extra character produces an error instead, and nothing reaches the next field.

Common causes

• You filled the field and kept typing the next value, expecting the cursor to move on by itself.
• You typed one character more than the field holds. The refused character may be a sign that your value is too long for the field.
• The display file sets CHGINPDFT(FE) at file or record level, so every input field needs a field exit key, and you are used to screens that advance on their own.

How to find the problem

1. Look at the cursor. It sits under the last character of a full field.
2. Press Help while 0018 is on the error line to see the system's text for the error.
3. In the display file source, look for CHECK(FE) on the field, or CHGINPDFT(FE) at record or file level.

How to fix it

• Press Reset (also called Error Reset) to free the keyboard. In many PC emulators Reset is the left Ctrl key by default. The value you typed is still in the field.
• Press Field Exit, Field+ or Field-, or a cursor movement key, to leave the field. Then type the next value.
• If the refused character was meant to belong to this field, the value is longer than the field. Check the value before you go on.
• For programmers, remove CHECK(FE) from fields where automatic advance is safe, and recreate the display file with CRTDSPF.
• For programmers, keep CHECK(FE) on fields where a value that spills over would be costly, such as quantities and amounts next to each other.

Technical reviewer: Albert Joseph, WND Software.

Last reviewed 2026-10-18 by the WND Software team. Written in our own words. For the full reference, check IBM’s 3270 or 5250 display documentation.