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Logical Type

  The logical data type is mainly used in conjunction with IF statements which select a course of action according to whether some condition is true or false. A logical variable (or array element) may be used to store such a condition value for future use. Logical variables and arrays are also useful when dealing with two-valued data such as whether a person is male or female, a file open or closed, power on or off, etc.

Some programmers seem reluctant to use logical variables and arrays because they feel that it must be inefficient to use an entire computer word of perhaps 32 bits to store just one bit of information. In fact the extra code needed to implement a more efficient data packing scheme usually wastes more memory than the logical variables would have occupied.

Helen Rowlands