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Lecture+5+Computerized+Systems - Computerized Systems...

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Unformatted text preview: Computerized Systems Lecture 5 Agenda Computerized Systems Audit Trail Data Input Data Storage/Access Data Processing Audit Trail Source Document Journal General Ledger Financial Statements Financial Statements General Ledger Journal Source Document Accountants should be able to trace in both directions. Example of Tracing an Audit Trail Verifying Accounts Receivable Accounts Receivable Control Account-General Ledger Accounts Receivable Subsidiary Ledger (sum of all customers' receivables) Sales Journal Sales Invoice Bill of Lading Cash Receipts Journal Deposit Slip Remittance Advice Computer-Based Systems The audit trail is less observable in computer-based systems than traditional manual systems. The data entry and computer programs are the physical trail. The data are stored in magnetic files. Data InputSource Data Automation Keyboard Turnaround documents Point-of-sale scanner Bar code scanner Radio-frequency identification (RFID) tag ATM Electronic Data Interchange (EDI) Controls over Data Inputs Well-designed documents and input screens Pre-numbered documents or system assigns sequential number to each new transaction Edit checks Completeness Field or mode check Range or limit check Validity check Controls over Data Inputs Transactions of one type may be grouped in a batch and entered into the system at the same time Batch Control Totals Record count Financial totals Hash totals File-Based System: Hierarchy of Data Storage Elements Database File Record Field Byte Bit Data Storage: File-Based Storage Master files Contain the balance or status of entities e.g., vendors, credit customers, inventory, assets, employees, general ledger Transaction files Contain activity data e.g., orders, sales, payments History or archive files Contain inactive past or historical data e.g., past financial statements, past transactions Reference files Contain information needed for reference purposes e.g., rates, prices, zip codes, chart of accounts Suspense files Contain items awaiting action, errors, missing information Record Structure Sources: James A. Hall Accounting Information Systems 2011 Storage and Access of Data Sequential Storage and Sequential Access Records are stored in order (by primary key) To access a record, the access device must read through all records that are stored previous to the desired record Tape cartridges and open reel tapes require sequential storage and sequential access of data Random Storage and Direct Access Records are stored at a unique location and the operating systems uses the address to retrieve a data record. Records are stored in any order Any record can be retrieved directly Computer disks allow random storage and direct access of data Storage Media Magnetic tape Generally used for data backup Sequential storage and sequential access If used for processing: Sorting is important Separate physical media is used for input and output in an update process Old master file, new master file Grandparent-parent-child backup Storage Media Digital (Disk) media Random storage and direct access Same physical media may be used for input and output in an update process Requires separate procedure to create back-up Data Processing Keeps data stored in databases current There are 3 types of processing: Updating Changing Adding Deleting Processing Methods Batch: accumulates transaction data for a period of time; all transactions are posted to the master file in one processing run On-Line, Real-time: transaction data are entered and processed to update the relevant master files and a response is provided to the person conducting the business event fast enough to affect the outcome of the event Combination: capture data electronically as transaction occurs, update some files as transactions occurs (real-time) and others later (batch) Batch Processing, Sequential File Journal Voucher Batch Sorted Journal Voucher Data General Ledger Master Edit input and update master file Key in journal Key in journal voucher data Voucher data Unsorted Journal Voucher data Sort voucher data in chart of account order Old General Ledger Master New General Ledger Master Sorted Journal Data Error and Exception Report Advantages and Disadvantages of Batch Processing Main Advantages: Increases efficiency by grouping large numbers of transactions for processing Relatively easy to design, program, and maintain Main Disadvantage: Stored data current only immediately after batch update Real-Time File Processing Journal Voucher Data Sale Transaction Log Input data (could use scanner) Error and Exception Message General Ledger Master File Edit data and update GL Master File (Journal Voucher file numerical order) N Advantages and Disadvantages of Real-Time Processing Main Advantage: No time lag between the economic event and processing Main Disadvantages: Higher cost of designing and maintaining Requires dedicated processing capacity May create operational inefficiencies Controls over Data Processing Controls designed to insure: All transactions are processed No transactions are added All transactions are processed correctly Controls over Data Processing (con.t) Batch Processing--Batch totals generated during processing to compare with batch input totals: Record count Financial totals Hash totals ...
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