Final answer:
The TAR master file stores historical transaction data, while the ETR master file stores real-time or current charges.
Step-by-step explanation:
Both the TAR master file and the ETR master file are used to store charges in computer systems and databases, but they have different functions.
The historical information of every transaction and charge made within a given time period is kept in the TAR master file (Transaction Archive), usually in chronological order. It can be thought of as an audit trail that records all prior charges along with pertinent data.
On the other hand, current or real-time charges are recorded as they happen in the ETR master file (Event Transaction Record). It serves as a real-time log of the current transactions and is updated with the most recent charges.