audit

1.  Data codes have two purposes:
1) Uniquely identify an entity or identify
an entity as a member of a group or set.
2) Identification purposes, codes often
are more compact than textual or
narrative description because they
require fewer characters to carry a given
amount of info.

2.  Addition: An extra character is added to
the code
 Truncation: a character is omitted.
 Transcription: a wrong character is
recorded.
 Transposition: Adjacent characters of
the code are reversed.
 Double transposition: characters
separated by one or more characters
are reversed.

3.  Length of the code: Longer codes are
more error prone. They should be broken
into chunks by using hyphens, slashes, or
spaces.
 Alphabetic / numeric mix: if alphabetic
and numeric characters are mixed in a
code, error rate is lower if alphabets are
grouped together and numeric are
grouped together.

4.  Choice of characters: If possible, the
characters B,I,O,S,V,Z should be avoided
because they frequently confuse with
characters 8,1,0,5,U, and 2.
 Mixing uppercase/lowercase fonts:
Having to use the shift key during keying
of a code breaks the rhythm and
increases the likelihood of error. Special
characters like @,*,# also cause
problem.
 Predictability of character sequence:
some character sequences are more
predictable than others and as such, are
less error prone.

5.  Serial codes: assign consecutive
numbers(or alphabetic) to an
entity, irrespective of the attributes of the
entity.
Advantage: Ease of addition of new
item and conciseness. Different users
might wish to view data differently. A
code that presumes one view of data
might be inappropriate for certain users.
Disadvantage: Creates problem when
file of item is volatile-i.e significant no. of
addition and deletion occur.

6. block sequence codes: assign
blocks of numbers to particular category
of an entity. Primary attribute on which
entities are to be categorized must be
chosen. And blaocks of numbers must
be assigned to customers on the basis of
the discount allowed each customer.
Advantage: have the advantages of
giving some mneumonic value to the
code.
Disadvantage: difficult to choose size
of the block needed.

7.  Hierarchical codes: Require
selection of the set of attributes of the
entity to be coded and their ordering by
importance. The value of code is a
combination of the value of the codes
for each attribute of the entry.
Advantage: Describe more attributes
of the entity which they apply.
Disadvantage: Not always concise.
They mix alphabets and numerics, which
undermine recall accuracy.

8.  Association codes: attributes of the
entity to be coded are selected. and
unique codes are then assigned to each
attribute value. Codes can be numeric
alphabetic or alphanumeric.
The code for the entity is simply the
concatenation of the different codes
assigned to the attributes of the entity.