Control break

Break (English control break ) is a term of data processing and refers to the situation in which a data set to be processed a sorted sequentially processed input dataset does not belong to the same grouping as the processed immediately beforehand. The associated processing principle is called the group control, group changing logic or break processing. A break processing is usually part of a batch program, usually a file is being processed. A break is when the concept of order of a data set is different from the preceding block. Such a change often requires special processing steps, such as the issuance of a total line of the previous group as well as the initialization of variables for the following group. Some high-level languages ​​( such as RPG or ABAP) offer built-in support of the group processing. Similarly, the treatment group change is supported by most report generators.

From a multi-level break occurs when more than one order term is to be applied. The order terms have to have a hierarchical dependency, that is, the records are sorted first by the first order term and within the first-order term after the second, etc. ensuring the correct ordering of the input data and determining the correct reading order (with simultaneous processing of multiple input files ) are in some problems with the break processing closely related (see also standardized programming).

History

When tabulating there is already the principle of break processing, the records be present in the form of punch cards. The first tabulating machine that enabled a group of regular treatment of punched cards, was developed by Herman Hollerith in 1914. This could reflect subordinate figures according to configurable aspects, which was mainly for the accounting of use. In 1936, the company DEHOMAG brought on the German market, the D11 out a Tabelleriermaschine that support a three-stage break. The punch cards had to be present sorted and mixed after the group criteria. Depending on the level of that break could form the D11 totals or cause a form feed at the Print List Output. The group criteria were doing configured via control panels ..

With the beginning of the computer age, as in the 1950 batch programs the dominant form of data processing represented, the break processing was a recurrent processing principle. Therefore, this standardized solution method were designed, such as the DIN 66260th By the 1980s since the years more and more important winning interactive dialogue processing the break processing plays a less dominant role.

Solution principle

The usual solution method provides two switched loops for a single-stage group change. The termination criterion of the outer loop is that no more records are available, that is, in a sequential file processing, that the end of file has been reached. The first record is read before the loop. Within this loop, the so-called group flow is first performed, this includes in particular the detention of the order criterion of the current record (for example, personnel number) in order to detect a change can. In addition, at this point all variables have to be initialized, which refer to the group temporarily, for example counter for summation and information that is still needed in later stages (eg, name and address of the employee ).

At the group advance to the inner loop joins. The termination criterion is the end of file, also also change the order of the criterion group as in the outer loop. In the inner loop, the actual processing of the sentence takes place, this may be the output of a row of data to a printer or updating of summary variables for the next higher group level to be. At the end of the inner loop of the next record from the file to be read.

If the termination criterion of the inner loop has been achieved, there is a change of the group, the current record is for this already in the following group. After the inner loop of the so-called group tracking is done ( sometimes called himself also " break "); this includes, for example, the issue of a total line for the group.

After reaching the termination criterion of the outer loop nor can a final processing can be performed, for example, the issue of a total row.

In a multistage group change is the processing portion of an outer group from the group exchange sequence of the inner group with flow, further nested loop and caster. The termination condition of the inner loop always include the outer, thus also changing the parent group criteria. Reading the next sentence will take place at the end of the innermost loop.