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SULPHUR AND ITS COMPOUND SULPHUR AND ITS COMPOUND:A.SULPHUR (S) Sulphur is an element in Group VI(Group 16)of the Periodic table . It has atomic number 16...





DATA PROCESISSING-Data processing deals with how data is organized & processed in the computer.


  • Data is a collection of facts & figures, which can be processed to produce information.
  • Data are the facts relating to an activity in a given environment.

The activity can be Accounting, Inventory control, etc.  Environment can be business, scientific, education, etc.


  • In an educational environment, when students sit for exams, the grades obtained represent the data to be processed by the computer. In this case, data can be Names of students & Marks
  • In a business environment, data can be the No. of Hours worked, names of employees, Stock Inventory levels, expense statements, etc.

Data can also be described as Raw data, if they are not yet processed, i.e. if they do not convey particular meaning to a given activity within any given environment.

It therefore means that, Data are unprocessed information consisting of details relating to business transactions.  For example, in a Payroll system, data are employee’s names, basic salary, department number, marital status, etc.


  • The collection, manipulation & distribution of data (i.e.) letters, numbers & graphic symbols, to achieve certain objectives.

The processing may involve calculations, comparisons, decision-making and/or any other logic to produce the required result.

  • The activity of manipulating the raw facts to generate a set of meaningful data (described as Information), which is able to convey some meaning.
  • Those activities, which are concerned with the systematic recording, arranging, filing, processing, and dissemination of facts relating to the physical events occurring in a business.

Data processing is a very important activity in any organization of any size or nature because it generates information for decision-making.

If the data processing uses complicated processing tools or aids, e.g. the computer, it is described as Electronic Data Processing (EDP).


  • Information is data, which is summarized and processed in the way you want it, so that it is useful in your work.
  • Information is an assembly of meaningful data items.

The information in Payroll activity includes; Net pay, Total Tax deductions, etc.  In Stock Control, the information generated includes; Closing stock, Total cost of the items, Purchases, Sales, etc.

The information is obtained by applying some processing procedures onto the raw data being input.  For example, to get the Net pay in a Payroll activity, the procedure would be;

Net pay = (Basic salary + Allowances + Overtime, if any) – Taxes.

Information is the end product of data processing available at the right place, the right time and in the right form.

The information generated by the data processing activities is very important in the working strategies of any organization, because it is used by the organization to make decisions.


Characteristics/ Features of good Information.

It should: –

  • Have and serve a purpose.
  • Be relevant to its purpose.
  • Be complete, accurate, and comprehensive.
  • Have been obtained from a reliable source.
  • Be communicated to the right person and in the right time (i.e. it should be timely).
  • Be clear and understandable by the user.
  • The user must have confidence in it.

Relationship between Data, Data Processing, and Information.

Data are the facts which relate to any particular activity, and do not have any specific meaning.

Information is data with a definite meaning.

Data processing is the process, which transforms data into information.

In a Manufacturing industry, data may be compared to raw materials and Information to finished products.  Just as raw materials are transformed into finished products, raw data are transformed into information.

In order to generate information from data items, a set of processing activities have to be performed on the data items in a specific sequence depending on the desired final result.  Performing these processes is known as Data processing.

Raw data
Data processing



  1. Define the term Data processing.
    1. Distinguish between the following terms:
  • Data processing.
  • Information
  1. Using examples, explain the difference between ‘Data’ and ‘Information’.



Data processing cycle refers to the various stages involved in converting data into information.

Basic stages in the Data processing cycle.

There are 5 primary elements/functions of data processing system.  They include; Input, Processing, Storage, Output, and Control.


Exercise I.

  1. (a). What is a Data Processing cycle.

(b). State and describe the stages involved in data processing cycle.

  1. Draw and label a clear flow diagram of the stages involved in a data processing cycle.
  2. List the various steps in the data processing cycle and briefly describe what happens at each stage.


Data Collection is the process involved in getting the data from the point of its origin to the computer in a form suitable for processing.

Note.  Data collection starts at the source of the raw data & ends when valid data is within the computer in a form ready for processing.


Data Entry:

Nowadays, most end-users input data to the computer using Keyboards on PCs, Workstations, or Terminals.

Data can originate in many forms, but the computer can only accept it in a machine-sensible form.

Problems of Data Entry.

  1. The data to be processed by the computer must be presented in a Machine-sensible form (i.e. in the language of a particular input device).

Note that most of the data originates in a form that is not machine-sensible.  Therefore, the data must undergo the process of Transcription before it is suitable for input to the computer.

  1. The process of Data collection involves getting the original data to the “processing center”, transcribing it, sometimes converting it from one medium to another, and finally getting it into the computer. This process involves a great number of people, many machines, and much expense.

Data Capture:

Data Capture is the process of obtaining data in a computer-sensible form at the point of origin.

Obtaining of data in a computer-sensible form helps to avoid many of the problems of data entry.

The captured data may be stored in some intermediate form for later entry into the main computer in the required form.  If data is input directly into the computer at its point of origin, the data entry is said to be On-Line.  In addition, if the method of direct input is a terminal or workstation, the method of input is known as Direct Data Entry (DDE).



The process of data collection may involve any number of the following stages depending on the methods used.

  1. Data Creation.

This involves 2 basic alternatives:

  • Source documents.

Source document is the original document used to record data and/or instructions. 

Most of the data is in form of a manually scribed or typewritten documents, i.e. the data is on clerically prepared source documents.

  • Data capture. This involves preparing the source document itself in a machine-sensible form so that it may be used as input to the computer without the need for transcription.  The prepared source document is then read directly by a suitable device, e.g. a Bar code reader.

 Data capture eliminates the need for transcription. 

Note.  The method and medium adopted for data creation will depend on factors such as Cost, Type of application, etc.

  1. Data Transmission.

This will depend on the method & medium of data collection involved/adopted.

If the computer is located at a central point, the documents will be physically “transmitted”, i.e. by the Post office or a Courier to the central point.

The data can also be transmitted by means of Telephone lines to the central computer.  In this case, no source documents would be involved in the transmission process.

  1. Data Preparation.

Data Preparation is the term given to the transcription of data from the source document to a machine-sensible medium.

There are 2 parts involved in the data preparation:

  • The original transcription itself, and
  • The Verification process that follows.
  1. Conversion of data from one medium to another.

Data is prepared in a particular medium & converted to another medium for faster input into the computer.

For example; data might be prepared on Diskette, or captured onto Cassette, and then converted to magnetic Tape for input.

The conversion will be done on a computer that is separate from the one for which the data is intended.

  1. The data, now in magnetic form, is put into the computer and subjected to validity checks by a computer program before being used for processing.


  1. This stage is required to re-arrange the data into the sequence required for processing.

Sorting is necessary for efficient processing of sequentially organized data in many commercial and financial applications.

In all the stages of data collection, control must be established and applied where necessary.  In other words, Control is usually applied through out the whole process of data collection.



The following are alternatives that can be used to collect data:

  • Use of Data Capture devices such as Scanners, Kimball Tags, Point-of-Sale systems, Bar-code readers & Magnetic strip readers.


The System designer must guard against the following types of errors:

  • Transcription (copying) errors.
  • Missing source documents.
  • Source documents whose entries are omitted, illegal and suspicious/doubtful.
  • Program faults (errors).
  • Machine hardware faults.

Note.  Machine hardware faults are less common because modern computers have self-checking facilities & usually signal any internal failure.


  • Accuracy:
  • Timeliness:
  • Relevance:



The quality of Input data is important to the accuracy of output.  Control must be instituted as early as possible in the system & everything possible must be done to ensure that data is complete and accurate before being input to the computer.

Objectives of Data Control.

The objectives of Control are:

  • To detect, correct and re-process all errors.
  • To ensure that all data is processed.
  • To preserve the integrity/reliability of maintained data.
  • To prevent and detect fraud/deception.

Note.  Control must be designed into the system & thoroughly tested.  Failure to build in adequate control may cause expensive systems to fail.  In addition, all users must be fully consulted to ensure that adequate controls are implemented.

Types of Data Controls.

The following are controls that can be used to ensure data accuracy:

  • Verification:

This is the process of checking & ensuring that data has been transcribed/ written out correctly.

Verification is whereby several computer users are given data to enter into the computer and the results are compared.  Or else, a second transcription is compared with the first one.  If the results are different, then there is inaccuracy in that data.

This method is mostly used to verify password changes.

Note.  Verification calls for manual intervention, hence errors are possible.  Note that some copying/transcription mistakes that bypass the verification stage are difficult to isolate during verification, e.g. the confusion of l (letter l) and 1 (one).  In this case, l might be input instead of 1 and vice versa, hence such mistakes go undetected.

The main types of errors, which might occur are: –

  • Missing data.
  • Duplicating of data.
  • Use of outdated records.
  • Incorrect batches of input data.
  • Incorrect recording at the source.
  • Incorrect data preparation.

Manual controls.

This involves considerable checking of the source documents.

Such checks may be:

  • Inspecting the source documents to detect missing entries, illegible entries, illogical or unlikely entries.
  • Comparing the document against stored data to verify entries.
  • Re-calculating to check calculations made on the document.



A Computer cannot notice errors in the data being processed in the way that a Clerk or Machine operator does.

Data validation is the process of preventing wrong data from being processed.  It involves checking whether the results generated by the computer are valid or applicable.  During input or data preparation, the data must be checked for transcription errors, through a process known as Verification.

Once the data is brought into the computer memory directly from an input device, immediately before processing, the data is again subjected to checks built in the program described as validation checks, to check the data integrity or the conformity of the data to the processing requirements.

Data validation includes testing for the following:

  • Test for reasonableness.

The computer program checks whether the data is reasonable, e.g., number of people should not be represented in decimals, i.e. 9½ children.

  • Test for numbers.

E.g., numbers should not be given as alphabets.

  • Test for alphabets.

E.g., alphabets should not be represented as numbers.

These checks can be made at 2 stages:

  • Input stage: When data is first input to the computer, different checks can be applied to prevent errors going forward for processing. For this reason, the first computer run is often referred to as Validation or Data vet.
  • Updating stage: Further checking is possible during data processing (or when the data input are being processed).

The program checks the consistency of the input data with existing stored data.  This check is possible during the input run if the stored data is on-line at the time.

Note.  Validation is an online process (i.e. validation checks are build into the computer programs using the input data, so that incorrect data items are detected and reported).  Since the checks are under the influence of the computer, they are not prone to errors.

Exercise I.

  1. Distinguish between Data verification and Validation as used in the context of data collection.




In Manual systems, the data processing activities are carried out manually by the human Clerks assisted by some calculating tools such as Slide rule, Logarithms, etc.

In individual business units, the transactions are recorded on the source documents, which are taken to the data processing department for processing.  Human beings work on source documents mentally or with the aid of some simple manipulation tools.

The files maintained are updated appropriately to reflect the correct image of the business.

The records are stored in form of Ledger cards, in the filing trays or in cabinets.  The Ledger cards contain the sales data (the amount owed by customers) and purchases data (the amounts owed to suppliers).

The Information (in the form of business documents) is generated, e.g., Statements of Accounts, and sent to the customers.

Control is carried out/ monitored by the Supervisor guided by the instructions written down in a Procedure manual.

In Manual systems, the data being used by one individual becomes inaccessible to another individual.


Mechanical systems are data processing systems whose activities are carried out by Keyboard devices operated by human beings.  The devices include; Accounting machines, Cash registers, Calculators, etc.

Data is keyed in by the Machine operator, manipulated by the machine, and the output is obtained in form of printed documents.

Once the machine is switched on & given the relevant instructions, it works on the data input automatically. 


Note.  The instructions, in this case, may be pressing the relevant Keyboard button, e.g. pressing the button for addition, after a set of values have already been keyed in or as they are being keyed in.

The control activity is carried out automatically by the machine itself or by a human machine-operator guided by the instructions laid down in a Procedure manual.  Other control strategies include; Self-experience on the job and Supervision.


Electronic Data Processing (E.D.P) systems use electronic machines, such as Computers, to process data.  This is because of the volume of data to be processed, and timing of the information expected from such processing activities.

Data that is to be input into an ED.P system should be first prepared into machine-sensible form.  This means that, data cannot be input directly through the terminal or Keyboard, connected online to the computer system.  In such a case, the Key-to-disk data preparation method could be used.  The contents of the disk are input using the reading/writing unit of the disk.  The disk pack is mounted onto its drive and the computer is activated to read or transfer the contents of the disk into its memory, where the data are held temporarily to await processing based on the instructions given.

The processing is done automatically by the computer under the influence of a set of instructions (programs).

The master files are stored in the mass storage media, e.g. Disk.  The disk contents are updated accordingly during the processing run.

The type of output generated by the E.D.P system is influenced by the type of output device used, e.g. hardcopy outputs are produced through the Printers, while Softcopies are produced through the Screen displays.

The control of the Electronic systems is automatic under the influence of the Control unit (CU) of the computer, whose actions are influenced by stored programs.


Comparison between Manual, Mechanical and Electronic Systems.


Functions Manual Systems Mechanical Systems Electronic Systems


–     Human observation

–     Keyboard

–     Written records

–     Human observation

–     Keyboard

–     Written records

–     Keyboard

–     Data entry terminals

–     Document readers



–     Human brain

–     Calculators

–     Written procedures

–     Conventional machines, e.g. Calculators, Cash registers, etc –     Computer’s C.P.U.


–     Human voice

–     Written documents

–     Calculator display.

–     Human voice

–     Written reports

–     Printed reports.

–     Visual Display unit

–     Voice Output

–     Printed output.

–     Photographed output.



–     Human brain

–     Manual files

–     Written records

–     Manual files or folders. –     Computer’s Main memory.

–     Storage media – disks, tapes, etc




–     Human brain

–     Written procedures on manuals.

–     Personnel experience.

–     Supervision.

–     Machine influence

–     Written procedures on manuals.

–     Personnel experience.

–     Supervision.

–     Computer’s Control unit (CU).

–     Stored programs.


Reasons for changing from Manual to Mechanical and Electronic Systems.

The following are the factors, which may necessitate the change from Manual to Mechanical or to Electronic data processing method:

  • Operation Speed.

The timing aspect of information availability (i.e. when the information is required) is very important.

Electronic & Mechanical systems provide automatic processing of the input data.  This quickens the operations on the input data to produce timely information.

For example, a Clerk assisted by mechanical or electronic devices takes shorter time to complete the posting of a transaction.

  • Accuracy of the information.

The use of mechanical or electronic data processing tools makes information more accurate & neat, by removing the use of illegible hand written entries.

In addition, verification is made easy; hence wrong data are easily prevented from entering the processing stage.

  • Volume of data.

The data processing method selected should be able to cope with the processing tasks, in respect to the data held.  The data (records) of an organization depends on the size & the nature of the business.

Small organizations with low volumes of data, require few personnel with little or no data processing aids.

Large or complex business organizations, with high volumes of data, require the use of sophisticated processing tools, if the information is to be produced on timE


Data processing that requires repeated operations may be boring & tedious when carried out manually.  In such a case, mechanical or computer machines may be employed to assist in the processing depending on the nature of the business.

  • Linked Applications.

In a situation where there is a common data pool that supports several applications, and e.g., Manual D.P method is used, then different operations may be required to produce different informations.  However, if Electronic D.P method is used, the informations can be easily produced from the same data.  This is because, the computer is versatile, and can operate in any desired manner provided the relevant programs are available.

  • Better services to customers.

As Data processing systems produce information, the recipient of such information should receive them immediately to enable them take decisions that control their business operations.

Using the sophisticated processing aids, such as Computer as in Electronic D.P systems, improves the quality of information produced, e.g. statistical summaries are produced in good time, enquiries are answered in good time, and orders are dispatched promptly.

Factors that determine the Methods of Data Processing.

The following are the factors that influence the method of data processing selected:

  • Size and Type of business.
  • Timing Aspects of the information produced from the system.
  • Link between Applications.

Size and Type of Business.

Simple or small business organizations require relatively fewer personnel and processing methods that are less complicated.

In a very small company, a single person can be used to produce all the information required, but as the volume of business increases, more people and tools/aids in the form of Calculators and small Computers may be employed.  Large volumes of data and information will require the use of large computers.


For example;

In some companies, the Payroll may involve paying a member of staff the same amount each month, while in others a complex payment system may be involved.

Similarly, producing an Invoice may be a matter of simply copying from the customer’s order, or it may require complex discount calculations.

Simple calculations indicate the need for fewer people and tools to produce the information, while complex situations indicate the need for more people and aids.

Timing Aspects of the information produced.

Some applications/ jobs require much shorter time between the origination of the transaction and the production of information (e.g. Hotel bookings), while other business applications may require the information to be made available after a relatively longer period, e.g. in Passport application, where information is required periodically.

Some information requirements are less important than others.  E.g., the Payroll and Statement of Accounts may only be produced once a month, whereas in certain companies, the Invoices may be produced all the time (i.e. as a customer collects the goods).

Link between Applications.

In some applications, the same data items may be used in producing more than one information; hence, the most suitable data processing system should be used depending on circumstances surrounding these information requirements.

E.g. a particular item sold may be needed to produce the Invoice & to amend the recorded Stock position (i.e. to make adjustment of Stock level, and the Bank account or Cash account).

Exercise I.

  1. Distinguish between Manual, Mechanical and Electronic systems.
  2. Describe the reasons for changing from Manual to Mechanized or Electronic systems.

Exercise II.

  1. Write short notes on the following:
  • Manual systems.
  • Mechanized systems.
  • Electronic systems.
  1. By use of a clear table and brief explanation, show the differences between manual, mechanized and electronic systems touching on the following functions: input, process, output, storage and control.                                                                   (20 marks).