With the advancement of the computing technologies，computer programs are more and more widely used in accounting system.There are several main advantages with a computerized accounting system(CAS):first，the transitions are simultaneously recorded in journal and posted electronically to general and subsidiary ledger accounts.The posting process is done without manual effort，since the original transitions include the required information for posting to the ledger.Thus，computerized accounting systems simples the recorded-keeping process.Moreover，CAS will not make common mistakes，such as math errors，costing errors and journal recording error.Thus CAS provide the management of current account balance information since the account balances are posted as the transitions occur and provide management of more current information to support decision making.Despite their many advantages，CAS are not without their problem:first，although a small company can purchase“off-the-shelf”software and have its system set up and run in a few days，system development and installation in a larger，more complex organization may take many months and cost millions of dollars.Such systems usually require an outside consultant for their design and implementation.Moreover，technological advances make existing systems obsolete within a few years， and much time and money must be spent to update them.Thirdly，unlike a manual system，a computer-based system does not leave a paper tail that can be readily audited，hence it is has a higher risk of causing business frauds and resultant failure.

This is the age of electronic commerce(EC).This fast-moving environment has engendered an array of innovative markets and trading communities.While EC promises enormous opportunities for consumers and businesses，its effective implantation and control are urgent challenges facing organization management and accountants.

To properly evaluate the potential exposures and risks in this environment，the modern accountant must be familiar with the technologies and techniques that underlie EC.Hardware failures，software errors，and unauthorized access from remote locations can expose the organization's accounting system to unique treats.For example，transactions can be lost in transit and never processed，altered and rearranged electronically to change their financial effect，corrupted by transient signals on transmission lies，and diverted to or initiated by the perpetrator of a fraud.Most entities use a computer to do their accounting.The computer has the following advantages over the manual system:the computer is much faster;the computer does not make copying error.For example，when the computer writes a check，the amount of the check is always the amount credited to the cash account and debited to some other account.The amounts reported on the financial statement are the same as the balances in the accounts.The computer ensures that debit entries always equal credit entries.It will not accept an entry in which this equality does not exist.Once an amount has been recorded in the computer，it may be used for several purposes.For example，an entry to Accounts Receivable is used in calculating the total amount in the Accounts Receivable account，the accounts of individual customers，and the amount reported on the balance sheet.The computer does not make arithmetic errors.The computer has build-in safeguards that may help detect fraudulent or erroneous entries.In a company at several locations，an entry generated at one location can be transferred accurately to the central chart of accounts via the Internet.Companies have a chart of accounts that gives an account number for every possible transaction in the system.This can help to ensure the tracking of information if it is necessary.