Single entry system is that system of book-keeping under which financial transactions are recorded without considering dual aspect. This means only one aspect if affected while keeping the record of financial transactions. It is not possible for the small organization to keep record of transaction using double entry system.
Statement of affairs is like a balance sheet. Under single entry system, statement of affairs is the list of assets and liabilities of a business organization in a given period. Capital is the difference between assets and liabilities.