The book in which all the accounts of a business using double-entry bookkeeping are contained. It is the ultimate record book, showing the consequences of all transactions entered into by the business. For practical purposes it is commonly split up into several books, e.g. the nominal ledger, the personal ledger, the private ledger and the cash book.
Although ledgers are still maintained manually in small businesses, the records which comprise the ledger are now more commonly kept by mechanical or electronic methods, and the greater part of the ledger of a large public company will consist either of cards continually updated in the process of machine accounting procedures or of detailed information stored in computer memory banks or on microfilm.
Reference: The Penguin Business Dictionary , 3rd edt.