Registers are classified according to function, content, and form. With those grouped according to function, a distinction is made between chronological, systematic, and combined registers. Chronological registers list transactions in chronological order or in the order in which the documents reach the accounting department. Systematic registers are used to record economic transactions of a similar type. Combined registers, for example, summary journals, are used to record all transactions in chronological order and to assign the transactions to the proper accounts.