【正确答案】(1) A documentary credit is a written undertaking by a banker who is the agent fro the importer or the buyer. The function of a documentary collection is to provide both importer (buyer) and exporter (seller) with a compromise to settle their trade transactions between payment in advance and on open account terms. 　　The parties involved in a documentary credit arrangement include issuing banker, advising banker, the applicant and the beneficiary. Parties involved in a documentary collection include the drawer (exporter or seller), the remitting bank, the collecting bank and the drawee (importer or buyer). . 　　Their processes are different. 　　(2) In accordance with the instructions of the importer, the bank undertakes to pay the exporter, up to a limit, within a designated time period and against any stipulated terms and documents. 　　The credit created for international settlement among banks not only provides a sense of security for the traders involved , but also a reliable source of finance for foreign trade where required . 　　(3) A "revocable credit" may be cancelled at any time up to the moment the advising bank pays. This type of credit is the least favorable to the exporter. 　　An irrevocable credit may not be amended or even cancelled without the consent of all the parties involved. This type of credit guarantees payment to the beneficiary, provided that the credit terms and conditions are met.