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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
  Input Human observationKeyboardWritten records Human observationKeyboardWritten records KeyboardData entry terminalsDocument readers
  Process Human brainCalculatorsWritten procedures Conventional machines, e.g. Calculators, Cash registers, etc Computer’s C.P.U.
  Output Human voiceWritten documentsCalculator display. Human voiceWritten reportsPrinted reports. Visual Display unitVoice OutputPrinted output.Photographed output.
  Storage Human brainManual filesWritten records Manual files or folders. Computer’s Main memory.Storage media – disks, tapes, etc
    Control Human brainWritten procedures on manuals.Personnel experience.Supervision. Machine influenceWritten 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.

  • Convenient.

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.

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

Exercise II.

  1. Write short notes on the following:
  2. Manual systems.
  3. Mechanized systems.
  4. Electronic systems.
  5. 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).
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