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Verification & Validation

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Batch processing
In a batch processing system, documents such as sales
orders are collected into batches of typically 50
documents. A data control clerk is responsible for:
­ Counting the documents
­ Checking each one visually to see that the customer has
entered essential details
­ Calculating a control total…

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Batch processing (continued)
A data control clerk is responsible for:
­ Filling in a batch header document to show, e.g.
· batch number
· number of documents in batch
· date received
· control total
· hash total
­ logging the batch in a log book

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Validation checks
Almost every field in a database can have some type of
validation to ensure that data entry is accurate.
­ Presence check
Certain fields such as customer number, item code, quantity
etc must be present.
­ Format check (also called picture check)
e.g. code may have a pattern…

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Validation checks
­ Specific options
e.g. Sex (M / F)
­ File lookup check
If the customer has filled in their customer number, the
computer can look this up on the customer file and display
the name and address. The data entry operator can check
that it tallies.
­ Look-up…

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Check digits
Code numbers are often lengthy and prone to error.
­ E.g. customer no., employee no. or product no.
One way of preventing these errors is to add an extra
digit to the end of a code number which has been
calculated from the digits of the code number.…

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Modulus-11 Check Digit
1. Each digit of the code number is assigned a `weight'. The
right hand (least significant) digit is given a weight of 2, the
next digit to the left 3 and so on.
2. Each digit is multiplied by its weight and the products
added together.
3.…

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Verification
Entering data twice and comparing the two
Common in batch processing for a second
data entry operator to key in a batch of data
to verify it
Example
­ When setting a password, you are usually asked to
key the password in a second time.
­ This is to…

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