A field indicator is defined by an entry in positions 69 and 70, 71 and 72, or 73 and 74 of the input specifications. The valid field indicators are:
You can use a field indicator to determine if the specified field or array element is greater than zero, less than zero, zero, or blank. Positions 69 through 72 are valid for numeric fields only; positions 73 and 74 are valid for numeric or character fields. An indicator specified in positions 69 and 70 is set on when the numeric input field is greater than zero; an indicator specified in positions 71 and 72 is set on when the numeric input field is less than zero; and an indicator specified in positions 73 and 74 is set on when the numeric input field is zero or when the character input field is blank. You can then use the field indicator to condition calculation or output operations.
A field indicator is set on when the data for the field or array element is extracted from the record and the condition it represents is present in the input record. This field indicator remains on until another record of the same type is read and the condition it represents is not present in the input record, or until the indicator is set off as the result of a calculation.
You can use halt indicators (H1 through H9) as field indicators to check for an error condition in the field or array element as it is read into the program.