Introduction

Data refers to the raw facts that do not have much meaning to the user and may include numbers, letters, symbols, sound or images.
Information refers to the meaningful output obtained after processing the data.
Data processing therefore refers to the process of transforming raw data into meaningful output i.e. information.
Data processing can be done manually using pen and paper. Mechanically using simple devices like typewriters or electronically using modern data processing tools such as computers.
Data processing cycle
- It refers to the sequence of activities involved in data transformation from its row form to information. it is often referred to as cycle because the output obtained can be stored after processing and may be used in future as input.
- The four main stages of data processing cycle are:
  - Data collection
  - Data input
  - Data processing
  - Data output

Data collection

Also referred to as data gathering or fact finding ,it involves looking for crucial facts needed for processing.

Methods of data collection

Include interviews; use of questionnaires, observation, etc.in most cases the data is collected after sampling.
Sampling is the process of selecting representative elements (e.g. people, organizations) from an entire group (population) of interest. Some of the tools that help in the data collection include source documents such as forms, data capture devices such as digital camera etc.

Stages of data collection

The process of data collection may involve a number of stages depending on the method used. These include:
- Data creation: this is the process of identification and putting together facts in an organized format. This may be in the form of manually prepared document or captured from the source using a data capture device such as a barcode reader and be inputted easily in a computer.
- Data preparation: this is the transcription (conversion) of data from source document to machine readable form. This may not be the case for all input devices. Data collected using devices that directly capture data in digital form do not require transcription.
- Data transmission: this will depend on whether data need to be transmitted via communication media to the central office.
1. Data input:
- Refers to the process where the collected data is converted from human readable from to machine readable form (binary form). The conversion takes place in the input device.
- Media conversion: data may need to be transmitted from one medium to another e.g. from a floppy disk to a computer’s hard disk for faster input.
- Input validation: data entered into the computer is subjected to validity checks by a computer program before being processed to reduce errors as the input.
- Sorting: in case the data needs to be arranged in a predefined order, it is first sorted before processing.
1. Processing
- This is the transformation of the input data by the CPU to a more meaningful output (information).Some of the operations performed on the data include calculations, comparing values and sorting.
1. Output
- The final activity in the data processing cycle is producing the desired output also referred to as information. This information can be distributed to the target group or stored for future use. Distribution is making information available to those who need it and is sometimes called information dissemination. This process of dissemination may involve electronic presentation over the radio or television, distribution of hard copies, broadcasting messages over the internet or mobile phones etc.

Description of errors in data processing

1. Computational errors
- Occurs when an arithmetic operation does not produce the expected results. The most common computation errors include overflow, truncation and rounding
- Overflow errors
- Occurs if the result from a calculation is too large to be stored in the allocated memory space. For example if a byte is represented using 8 bits, an overflow will occur if the result of a calculation gives a 9-bit number.
- Truncation errors
- Result from having real numbers that have a long fractional part which cannot fit in the allocated memory space. The computer would truncate or cut off the extra characters from the fractional part. For example, a number like 0.784969 can be truncated to four digits to become 0.784
The accuracy of the computer output is critical. As the saying goes garbage in garbage out (GIGO),the accuracy of the data entered in the computer directly determines the accuracy of the information given out.

Some of the errors that influence the accuracy of data input and information output include

Transcription,
Computation and
Algorithm or logical errors.

2.Transcription errors

Occurs during data entry. Such errors include misreading and transposition errors
Misreading errors
Are brought about by the incorrect reading of the source by the user and hence entering wrong values. For example a user may misread a handwritten figure such as 589 and type S89 instead i.e. confusing 5 for S.

Transposition errors
Results form incorrect arrangement of characters i.e. putting characters in the wrong order. For example the user might enter 396 instead of 369.
These errors may be avoided by using modern capture devices such as bar code readers, digital cameras etc which enter data with the minimum user intervention.

Rounding errors
Results from raising or lowering a digit in a real number to the required rounded number. for example, to round off 30.666 to one decimal place we raise the first digit after the decimal point if its successor is more than or equal to five. In this case the successor is 6 therefore 30.666 rounded up to one decimal place is 30.7.if the successor is below five,e.g.30.635,we round down the number to 30.6

Algorithm or logical errors
- An algorithm is a set of procedural steps followed to solve a given problem. Algorithms are used as design tools when writing programs. Wrongly designed programs would result in a program that runs but gives erroneous output. Such errors that result from wrong algorithm design are referred to as algorithm or logical errors.

Data integrity

Data integrity refers to the accuracy and completeness of data entered in a computer or received from the information system. Integrity is measured in terms of accuracy, timeliness and relevance of data.

Accuracy
It refers to how close an approximation is to an actual value. As long as the correct instructions and data are entered, computers produce accurate results efficiently. In numbers, the accuracy of a real number depends on the number. For example, 72.1264 is more accurate than 72.13.

Timeliness
This is the relative accuracy of data in respect to the current state of affairs for which it is needed.
This is important because data and information have a time value attached to them. If received late, the information may have become useless to the user. For example, information in the newspaper that is meant to invite people for a meeting or occasion must be printed prior to the event and not later.

Relevance
Data entered into the computer must be relevant so as to get the expected output. In this case, relevance means that the data entered must be pertinent to the processing needs at hand and must meet the requirements of the processing cycle. The user also needs relevant information for daily operations or decision making.

Threat to data integrity

Threats to data integrity can be minimized through the following ways:
Backup data preferably on external storage media.
Control access to data by enforcing security measures.
Design user interfaces that minimize chances of invalid data entry.
Using error detection and correction software when transmitting data
Using devices that directly capture data from the source such as bar code readers, digital cameras, and optical scanners.

Data processing methods

As mentioned earlier, data can be processed manually, mechanically and electronically.

Manual data processing

In manual data processing, most tasks are done manually with a pen and a paper. For example in a busy office, incoming tasks (input) are stacked in the “tray” (output). The processing of each task involves a person using the brain in order to respond to queries.
The processed information from the out tray is then distributed to the people who need it or stored in a file cabinet.

Mechanical data processing

Manual is cumbersome and boring especially repetitive tasks. Mechanical devices were developed to help in automation of manual tasks. Examples of mechanical devices include the typewriter, printing press, and weaving looms. Initially, these devices did not have electronic intelligence.

Electronic data processing

For a long time, scientists have researched on how to develop machine or devices that would stimulate some form of human intelligence during data and information processing. This was made possible to some extent with the development of electronic programmable devices such as computers.
The advent of microprocessor technology has greatly enhanced data processing efficiency and capability. Some of the micro processor controlled devices include computers, cellular(mobile) phones, calculators, fuel pumps, modern television sets, washing machines etc

Computer files

A file can be defined as a collection of related records that give a complete set of information about a certain item or entity. A file can be stored manually in a file cabinet or electronically in computer storage devices.
Computerized storage offers a much better way of holding information than the manual filing system which heavily relies on the concept of the file cabinet.

Some of the advantages of computerized filing system include:

information takes up much less space than the manual filing
it is much easier to update or modify information
it offers faster access and retrieval of data
It enhances data integrity and reduces duplication
It enhances security of data if proper care is taken to secure it.

Elements of computer file

A computer file is made up of three elements: characters, fields and records.

Characters
A character is the smallest element in a computer file and refers to letter, number or symbol that can be entered, stored and output by a computer. A character is made up of seven or eight bits depending on the character coding scheme used.

Field
A field is a single character or collection of characters that represents a single piece of data. For example, the student’s admission number is an example of a field.

Records
A record is a collection of related fields that Represents a single entities, e.g. in a class score sheet, detail of each student in a row such as admission number, name, total marks and position make up a record.

Logical and physical files

Computer files are classified as either physical or logical

Logical files
A computer file is referred to as logical file if it is viewed in terms of what data item it contains and details of what processing operations may be performed on the data items. It does not have implementation specific information like field, data types, size and file type.

Physical files
As opposed to a logical file, a physical file is viewed in terms of how data is stored on a storage media and how the processing operations are made possible. Physical files have implementation specific details such as characters per field and data type for each field.

Types of Computer Processing Files

There are numerous types of files used for storing data needed for processing, reference or back up. The main common types of processing files include

Master files,
Transaction,
Reference,
Backup, report and
Sort file.

Master file

A master file is the main that contains relatively permanent records about particular items or entries. For example a customer file will contain details of a customer such as customer ID, name and contact address.

Transaction (movement) file

A transaction file is used to hold data during transaction processing. The file is later used to update the master file and audit daily, weekly or monthly transactions. For example in a busy supermarket, daily sales are recorded on a transaction file and later used to update the stock file. The file is also used by the management to check on the daily or periodic transactions.

Reference file

A reference file is mainly used for reference or look-up purposes. Look-up information is that information that is stored in a separate file but is required during processing. For example, in a point of sale terminal, the item code entered either manually or using a barcode reader looks up the item description and price from a reference file stored on a storage device.

Backup file

A backup files is used to hold copies (backups) of data or information from the computers fixed storage (hard disk). Since a file held on the hard disk may be corrupted, lost or changed accidentally, it is necessary to keep copies of the recently updated files. Incase of the hard disk failure, a backup file can be used to reconstruct the original file.

Report file

Used to store relatively permanent records extracted from the master file or generated after processing. For example you may obtain a stock levels report generated from an inventory system while a copy of the report will be stored in the report file.
Sort file
It stores data which is arranged in a particular order.

Used mainly where data is to be processed sequentially. In sequential processing, data or records are first sorted and held on a magnetic tape before updating the master file.

File organization methods

File organization refers to the way data is stored in a file. File organization is very important because it determines the methods of access, efficiency, flexibility and storage devices to use. There are four methods of organizing files on a storage media. This include:

sequential,
random,
serial and
indexed-sequential

Sequential file organization

Records are stored and accessed in a particular order sorted using a key field.
Retrieval requires searching sequentially through the entire file record by record to the end.
Because the record in a file are sorted in a particular order, better file searching methods like the binary search technique can be used to reduce the time used for searching a file .
Since the records are sorted, it is possible to know in which half of the file a particular record being searched is located, Hence this method repeatedly divides the set of records in the file into two halves and searches only the half on which the records is found.
For example, of the file has records with key fields 20, 30, 40, 50, 60 and the computer is searching for a record with key field 50, it starts at 40 upwards in its search, ignoring the first half of the set.

Advantages of sequential file organization

The sorting makes it easy to access records.
The binary chop technique can be used to reduce record search time by as much as half the time taken.

Disadvantages of sequential file organization

The sorting does not remove the need to access other records as the search looks for particular records.
Sequential records cannot support modern technologies that require fast access to stored records.
The requirement that all records be of the same size is sometimes difficult to enforce.

Random or direct file organization

Records are stored randomly but accessed directly.
To access a file stored randomly, a record key is used to determine where a record is stored on the storage media.
Magnetic and optical disks allow data to be stored and accessed randomly.

Advantages of random file access

Quick retrieval of records.
The records can be of different sizes.

Serial file organization

Records in a file are stored and accessed one after another.
The records are not stored in any way on the storage medium this type of organization is mainly used on magnetic tapes.

Advantages of serial file organization

It is simple
It is cheap

Disadvantages of serial file organization

It is cumbersome to access because you have to access all proceeding records before retrieving the one being searched.
Wastage of space on medium in form of inter-record gap.
It cannot support modern high speed requirements for quick record access.

Indexed-sequential file organization method

Almost similar to sequential method only that, an index is used to enable the computer to locate individual records on the storage media. For example, on a magnetic drum, records are stored sequential on the tracks. However, each record is assigned an index that can be used to access it directly.

Electronic data processing methods

There are several ways in which a computer, under the influences of an operating system is designed to process data.
Examples of processing modes are:

online processing
real time processing
distributed processing
Time sharing
Batch processing
multiprocessing
multitasking
interactive processing

Online processing

In online data processing data is processed immediately it is received. The computer is connected directly to the data input unit via a communication link. The data input may be a network terminal or online input devices attached to the computer.

Real-time processing

Computer processes the incoming data as soon as it occurs, updates the transaction file and gives an immediate response that would affect the events as they happen.
This is different from online in that for the latter an immediate response may not be required.
The main purpose of a real-time processing is to provide accurate, up-to-date information hence better services based on a true (real) situation.
An example of a real time processing is making a reservation for airline seats. A customer may request for an airline booking information through a remote terminal and the requested information will be given out within no time by the reservation system. If a booking is made, the system immediately updates the reservation file to avoid double booking and sends the response back to the customer immediately.

Distributed data processing
Multiprogramming, also referred to as multitasking refers to a type of processing where more than one program are executed apparently at the same time by a single central processing unit.Distributed data processing refers to dividing (distributing) processing tasks to two or more computer that are located on physically separate sites but connected by data transmission media.

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DATA PROCESSING