Students' Guide to Information Technology, 2nd Edition

Computer

software

Le.

its program code, must be such as enable it to respond to

messages sent to it.

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Inheritance

- classes form hierarchies with ancestors and

descendants.

For example, the class 'accounts' may have as its

descendants 'customer accounts', 'supplier accounts' and so on,

and customer accounts may have as descendants 'credit

customers' 'cash-only customers', etc. Descendant classes are

able to call upon the services offered by ancestor classes as well

as offering services of their own. When an object receives a

message, if it does not contain the code enabling it to respond to

the message it forwards the message up the ancesto ...