Page 157 - DCAP507_SYSTEM_SOFTWARE

Unit 10: Programming Languages Concept (I)

The type boolean Notes

This type allows only two values true or false. So a boolean variables can assume one of two
values true or false.

The type double

It is an advancement of the type float. In this case, the length of signed or unsigned decimal
numbers can be larger than that of float type. These are called as double precision numbers.

Example: of this data type are:
23512.6732469, -6712345.98765

10.3.2 User-defined Data Types

Both languages provide facilities for declaring and defining new data types by the user.
In PASCAL, these are:
(i) Enumerated data type

(ii) Subrange data type
In case of language C, these are:
1. Enumerated data type
2. By using typedef statement

Enumerated Data Type

An enumerated data type is a user created data type in which the values, appropriate to the
datatype, are specified in a user-defined list. The syntax is:
PASCAL:
Type Enumerated-type-identifier (i1, i2, i3,à.in);
Type : Reserved word
Enumerated-type-identifier : Identifier
i1, i2, i3,à.in : Item list

The item-list constitutions the allowed values which the enumerated type variable can assume.
For example,
Type
MONTHS= (JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC);
Enumerated data type item list

Now, variables of type MONTHS can be defined as
Var A, B, C: MONTHS;
Thus A, B & C can have the values defined by the item-list.

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