Software Engineering – Input & Output Design

Input Design 

Introduction :

Input design involves capturing data as well as inputting it to the computer.

Accordingly input design consists of data capturing and data validation.

Data Capture :

Data capture covers all the stages from the recording of basic data to the feeding if this data into the computer for processing.


  • Reduction in the volume of input to the extent possible.
  • Lesser manual preparation
  • An input design will ease the work of the person engaged in input Preparation.
  • Minimizing the number of steps practicable in the data capturing process.

Basic steps in data capture:

  • Original recording
  • Data transmission
  • Data preparation
  • Verification
  • Sorting
  • Control
  • Computer input  

Data Validation :

The objective of a data validation system is to detect errors at the earliest possible stage before costly activities are performed in invalid data.

Some data validation is done by way of manual verification in data capture stage. Still there may be incorrect batched if input data, missing data, duplicated data and incorrect file record.

Therefore it is necessary that before data is first input to the computer for processing different checks are carried out. These checks are classified valid and invalid data.

These checks are as under:

Validation Checks:

Field checks

  • Limit/range check (Salary must be within 0 to 15000)
  • Picture checks (E.g. Pic of Emp no is AAA999 then PRD4N4 will be rejected)
  • Valid code checks (E.g. Designation must be clerk, manager or assistant)
  • Check digit (used to check transcription and transposition error)
  • Arithmetic check (Used to check the validity of a result)
  • Cross check (used to verify fields appearing in different files to verify result)

Transaction Checks

  • Sequence checks (E.g. to check whether any employee missed out from payment of salary)
  • Format completeness (used to check presence of all the transaction)
  • Redundant data checks (used to check the validity of reference to description)
  • Combination checks (E.g. Whether the number in digit and words are same or not)
  • Probability checks (used to avoid unnecessary rejection of data)
  • Passwords (used to check entry of data by unauthorized persons)
  • Checks (used to check that transaction pertains to the current period)
  • Batch total (used to check that transaction have been transcribed (recorded) correctly or not)
  • Hash total (used to verify that the transaction have been transmitted correctly)

Output Design 

Introduction :

Output is dependent on input. There is principle known as” Principle of starting without output”.

This means that organizations output needs should be considered first before devising appropriate methods and procedures, databases, planned inputs and effective internal control.

Design Principles :

  • Principle of starting without output.
  • Principle of acceptability of reports.
  • Principle of timely output.
  • Principle of enhancing the decision making process.
  • Principle of practicing “Management by Exception”.
  • Principle of duplication reduction in report.
  • Principle of simplicity in reports.

Objective :

Convey information about

  • Past activities: vendor history
  • Current status: inventory on hand
  • Future projection: sales or cost of manufacturing a new item
  • Confirm an action: completed task
  • Trigger an alarm: market loss
  • Signal events: through exception reporting or report by waiting Opportunities etc.

Types of Output:

  • External output: Invoices, Tax returns, pay slips, etc.
  • Internal outputs: Used within the users’ organization. E.g. Inventory reports, etc.
  • Operational outputs: Use is limited to the computer departments. E.g. Program listing
  • Interactive outputs: This involves user communicating directly with the computer.
  • Turnaround outputs: This will be a document containing data before submission for the further process.

Output Media:

  1. Printed output: Devices uses are line printer, dot matrix printer, etc.
  2. Visual output : Airlines and hotel reservation system
  3. Turnaround document output: Employee time card, credit card billing, etc.
  4. Secondary storage output: magnetic disk, magnetic tapes, etc.
  5. Micro film or microfiche output: are generally taken out on magnetic tapes.
  6. Audio response output: Banking system provides the balance of the customer’s account.

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