SAD-Input Design

Inaccurate input data are the most common cause of errors in data processing. Errors entered by data entry operators can be controlled by input design. Input design is the process of converting user-originated inputs to a computer-based format. The information for the input design is obtained from the data flow diagram and the system flowchart.

Input data

The goal of designing input data is to make data entry as easy, logical, and free from errors as possible .In entering data, operators need to known the following:
The allocated space for each field.
Field sequence, which must match that in the source document.
The format in which data fields are entered. For ex; filling out the date field is required through the edited format mm/dd/yy.

Source Documents

Source data is initially captured on paper or a source document.  Example: A cheque written against an account.  Source documents can be entered into the system through punch cards, diskettes or through keyboards.


1.Should be logical and easy to understand.
2.Should be clear.
3.Should specify to the user what to write and where to write.

Input media and devices

Source data are input into the system in a variety of ways. The following media and devices are suitable for operation:

1.Punch cards are either 80 or 96 columns wide. Data are arranged in a sequential and logical order. Operations use a keypunch to copy data from source documents onto cards. This means that the source document and card design must be considered simultaneously.

2.Key-to-diskette is modeled after the keypunch process. A diskette replaces the card and stores op to 325,000 characters of data-equivalent to the data stored in 4050 cards. Like cards, data on diskettes are stored in sequence and in batches.

3.MICR translates the special fonts printed in magnetic ink on checks into directed computer input.

4.Mark-sensing readers automatically convert pencil marks in predetermined locations on a card to punched holes on the same card.

5.Optical character recognition (OCR) readers are similar to MICR readers, except that they recognize pencil, ink, or characters by their configuration rather than their magnetic pattern. They are often used in remote locations as free standing input preparation devices or direct input media to the system.

6.Optical bar code readers detect combination of marks that represent data. The most widely known system is the Universal product code (UPC), Which codes retail items in stores. Automatic tag reading is a major breakthrough in speeding up customer service and eliminating costly data input errors at a point of sale.

7.Cathode-ray tube (CRT) screens are used for online data entry. CRT Screen display 20,40, or 80 characters simultaneously on a television like screen. They show as many as 24 lines of data.

In addition to determining record media, the analyst must decide on the method of input and the speed of capture and entry into the system. Processings may be
  •  Batched ( a group of records handled as a unit)
  •  Online ( records that are processed directly)
  •  Sequential ( sorted records)
  •  Random (unsorted records).
Online data entry

CRT screens are used mostly for online data entry. As terminal prices decline and microcomputers are commonly used, entering data directly through the keyboard is becoming popular.

Examples: Automated teller machines (ATMs) in banking  Point of sake (POS) in retailing.

Online data entry makes use of a processor that accepts commands and data from the operator through a keyboard, touch sensitive screen or a voice input. The input is analyzed by the processor and is accepted or rejected. There are three major approaches for entering data into the computer:

1. Menu
2. Formatted forms
3. Prompts. 
Menu: A menu is a selection list that simplifies computer data access or entry. Instead of remembering what to enter, the user chooses from a list of options and types the option letter associated with it. A menu limits a user’s choice of responses but reduces the chances for error in data entry.
In the above example the user can select any option manipulate on customer files. 

The formatted form: A formatted form is a preprinted form or a template that requests the user to enter in appropriate locations. It is a Fill-in the blank type form. The form is flashed on the screen as a unit. The cursor is usually positioned at the first blank. After the user responds by filling in the appropriate information, the cursor automatically moves to the next line and so on until the form is completed. During this routine, the user may move the cursor up, down, right, or left to various locations for making changes in the response.
The above example shows how to add customer details

The prompt. In prompt the system displays one inquiry at a time, asking the user for a response. After giving response the system will again display another inquiry, askng the user for a response. Most systems edit the data entered by the user.

In the above example the words in bold denote the system generated messages and the others represent user generated messages.

CRT Screen Design:

Many online data entry devices are CRT screens that provide instant visual verification of input data . The operator can make any changes desired before the data go to the system for processing CRT screen is actually a display station that has a buffer for storing data. A common size display is 24 rows of 80 characters each or 1920 character.

There are two methods for entering data on CRT screens
1.Manual method: The manual method uses a worksheet similar to a printout chart. The menu or the data to be displayed is blocked out in the reserved areas.

Example: In dBase the command to print “Hello” in the 10th  row and 10th column is as follows
 @ 10,10 SAY “HELLO”

The main objective of screen display design is simplicity and accurate and quick data capture or entry. Some of the guidelines to be followed are:
1.Use the same format throughout the project.
2.Allow ample space for the data. Overcrowding causes eyestrain.
3.Provide help or tutorial for technical terms or procedures.

2.Software utility method: This method designs screen layouts through software utility.

Example: IBM provides a Screen Design Aid  (SDA) package that allows the designer to modify the display components.
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