The concept of Data Processing

INPUT DESIGN Input Data Persistent Data Process Output

Why be concerned about INPUT DESIGN? Garbage In - Garbage Out (GIGO) Data Verification & Validation (V&V): Self-checking digits or check-digit Combination check Limit and Range checks Completeness checks

“Input” involves 3 steps: Batch On-Line (real-time) Hybrid “Input” Methods: 1. Collecting 2. Entering 3. Processing

BATCH INPUT - ADVANTAGES Collecting and Entering can be done off-line. Entering data can be done by trained personnel. Processing can be done very quickly. Processing can be done during non-peak times.

BATCH INPUT - DISADVANTAGES Data collection usually has to be a centralized activity. Data entry usually needs to be done by specially trained personnel. The processing activity is delayed, hence the possibility exists for data to be considered old or untimely when it finally gets processed. Since processing is usually done during off-hours, input errors detected during processing would not get corrected until the next regularly scheduled processing of input data. The off-hours computer operator may have to call the systems analyst or programmer if the program malfunctions.

ON-LINE INPUT - ADVANTAGES The data can be entered by its owners. The data can be entered as close to their origination as possible. Immediate feedback can usually be given regarding the correctness and acceptability of the data. The input data can immediately update a database thus making it as current as possible.

ON-LINE INPUT - DISADVANTAGES Equipment may be more costly to perform the input. Users are not always well trained to input data. User data entry procedural controls may be lacking. Software must have additional controls to handle it. Data is often only entered during business hours thus impacting the normal computer load. The data entry activity could actually be slower than the equivalent batch processing for the same data.

Batch vs. On-Line Transaction Processing Two types of TPS: –Batch processing »A system whereby business transactions are accumulated over a period of time and prepared for processing as a single unit or batch –On-line transaction processing (OLTP) »A system whereby each transaction is processed immediately, without the delay of accumulating transactions into a batch

Batch Schematic Data entry of accumulated transactions Input (batched) Output

On-line Schematic Output Terminal Immediate processin g of each transactio n

 There are three main ways to access data, depending on the storage device that has been used and the way that the data has been saved… Accessing Data 1. Direct Access 2. Serial Access 3. Sequential Access  To access data means to retrieve it from storage and place it in RAM, so that it is ready to be processed.

 Hard drives, optical drives, flash drives and almost all other storage devices are direct access devices (also know as random access). This means that data stored anywhere on the device can be accessed in an equally short period of time. Direct Access  Direct access devices are much quicker and more efficient than serial access devices, such as magnetic tapes which are only used for backup and archive purposes.  The location of each file is stored in a ‘table’ on the drive (called a FAT – File Allocation Table), which enables the operating system to find the file quickly.

Serial or Sequential Access  Magnetic tape is a serial access or sequential access device. This means that you have to wind through it to reach the data that you require. Access time varies depending on where the data is located on the tape.  Serial access is where the data is stored in the order that the data files were created, one after the other.  Sequential access is where the data is stored in a logical order, e.g. the records of a bank may be stored in numerical order by account number, or in alphabetical order by surname of the account holder.

 When data is stored in a computer system, there are two main things you can do with it – you can process it in the CPU, then you can output the results. Data Processing  There are many different ways of processing data… 1. Real-Time Processing 2. Interactive Processing 3. Batch Processing 4. Transaction Processing

 Real-time processing involves processing the data immediately, e.g. Real-Time Processing  Processing the data immediately makes sure: That the flight data displayed on the instruments is current, so that the pilot can operate the aircraft controls with confidence. Computer control, e.g. aircraft, robot, flight simulator  Real-time processing gives instant feedback.

 Interactive processing (also known as online processing) accepts and processes data items piece by piece and may produce prompts in response to each stage, e.g. booking a holiday… Interactive Processing  Departure Airport…  Departure Date…  As soon as all the data is entered, the holiday will be booked so that no double-booking occurs.  Destination Airport…  Arrival Date…  The processing for booking systems is not as urgent as for real-time processing – if the system is busy, the user can wait a little.  At this point the system may prompt the user, “There are no available flights for those dates…”

 Batch processing waits until a group of data files is ready to be processed, then processes them all at once. Batch Processing A business sending overdue letters to its creditors.  Batch processing is usually done at night or at weekends to avoid busy system times, as batch processing uses the CPU intensively and will slow down the system for other users.  Batch processing suits large volume tasks that have to be done at regular intervals, e.g. A council sending out council tax bills. A business sending out direct mail using a mail merge with its customer database.

 Transaction processing is where an individual file is processed as a one- off, e.g. Transaction Processing A library customer may return a book late. The librarian will process the request to return the book. This process cannot be done through batch processing because… The request is processed as a one-off transaction, and the amount owing is calculated.  The customer may owe money, and must pay before they leave.  Credit and debit card expenditure uses transaction processing as the bank needs to know straightaway when a customer has reached their credit limit.

Chapter Summary Processing Methods Online vs. Batch Processing

On-line processing System in which transactions are processed when and where they occur, allows output directly to end users –also called online transaction processing or interactive processing

On-line processing workstation -- either a PC or terminal connected to online processing system –online processing system verifies the transaction values and allows end user to interactively enter data and correct errors

On-line processing Online file -- data file with direct or indexed organization that allows random access –sequential files not used for online processing IS must be continuously available whenever end users require processing of transactions

Batch Processing IS in which data is collected and, at some later time, all the data that has been gathered is processed as a group, or batch Used extensively in 1950’s- 60’s Still used today for many applications

Batch Processing Any application that requires periodic processing of a large number of records is good candidate for batch processing –payroll –billing/invoicing –hard copy reports

Today’s processing trends Online and batch processing combined in single IS –random access files are available for transactions that require interaction –actual files available off-line for large batch processing –copies of online files available for batch reports that don’t require update

Online vs. Batch Online Advantages –data is entered and validated as it occurs –data is available sooner in more accurate form –data is up-to-date

That’s all folks!