Batch processing is a technique in which transactions are collected into groups, or batches, to be processed at a time when the computer may have few online users and thus be more accessible, usually during night. Unlike transaction processing, which we will examine momentarily, batch processing includes no direct user interaction. The master file is a semi-permanent set of records. The transaction file contains all the changes to be made in the master file: additions, deletions, and revisions. Periodically, perhaps monthly or weekly, the master file is updated with the changes called for in the transaction file. The result is a new, up-to-date master file.

     In batch processing before a transaction file is matched against a master file, the transaction file must be sorted so that all the transactions are in sequential order according to a key field.

     During processing, the computer matches the keys from the master and transaction files, carrying out the appropriate action to add, revise or delete. At the end of processing, a newly updated master file is created; in addition an error report is usually printed. Th