A control level indicator is defined by an entry in positions 63 and 64 of the input specifications, designating an input field as a control field. It can then be used to condition calculation and output operations. The valid control level indicator entries are L1 through L9.
A control level indicator designates an input field as a control field. When a control field is read, the data in the control field is compared with the data in the same control field from the previous record. If the data differs, a control break occurs, and the control level indicator assigned to the control field is set on. You can then use control level indicators to condition operations that are to be processed only when all records with the same information in the control field have been read. Because the indicators stay on for both total time and the first detail time, they can also be used to condition total printing (last record of a control group) or detail printing (first record in a control group). Control level indicators are set off before the next record is read.
A control break can occur after the first record containing a control field is read. The control fields in this record are compared to an area in storage that contains hexadecimal zeros. Because fields from two different records are not being compared, total calculations and total output operations are bypassed for this cycle.
Control level indicators are ranked in order of importance with L1 being the lowest and L9 the highest. All lower level indicators are set on when a higher level indicator is set on as the result of a control break. However, the lower level indicators can be used in the program only if they have been defined. For example, if L8 is set on by a control break, L1 through L7 are also set on. The LR (last record) indicator is set on when the input files are at end of file. LR is considered the highest level indicator and forces L1 through L9 to be set on.
You can also define control level indicators as record identifying or resulting indicators. When you use them in this manner, the status of the lower level indicators is not changed when a higher level indicator is set on. For example, if L3 is used as a resulting indicator, the status of L2 and L1 would not change if L3 is set on.
The importance of a control field in relation to other fields determines how you assign control level indicators. For example, data that demands a subtotal should have a lower control level indicator than data that needs a final total. A control field containing department numbers should have a higher control level indicator than a control field containing employee numbers if employees are to be grouped within departments (see Figure 15).