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Lecture 5 Computerized Systems-Student

Lecture 5 Computerized Systems-Student - Computerized...

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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. Sampling and confirmation are two common techniques. How does this trail differ in a computerized system? 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 Cash Prelist Remittance Advice 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 (details later) 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: 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 Transaction files Contain activity data History or archive files Contain inactive past or historical data Reference files Contain information needed for reference purposes Suspense files Contain items awaiting action, errors, missing information Record Structure Sources: James A. Hall Accounting Information Systems 2008 Storage and Access of Data Sequential Storage and Sequential Access Records are stored in order (by primary key) To access a record, 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 hard disks, floppy disks, CD-ROMs, and DVDROMs 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 Processing Methods Batch: accumulates transaction data for a period of time; all transactions are posted to the master file in one processing run 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) Flowchart Symbols Batch Processing, Sequential File Real-Time File Processing Advantages and Disadvantages of Batch Processing Main Advantages: Main Disadvantage: Advantages and Disadvantages of Real-Time Processing Main Advantage: Main Disadvantages: Controls over Data Processing Controls designed to insure: ????? Controls over Data Processing Batch Processing--Batch totals generated during processing to compare with batch input totals: ...
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