IB Statements/testbit

From CometWiki

TESTBIT function

Discussion: The TESTBIT function returns the value of a specified bit in a string expression.

Syntax: Result = TESTBIT(string-expression, bit-location [,EXCP=label])

Where:

Result is the value (0 or 1) of the bit at the specified bit-location.

String-expression is a string value encoded in binary form.

Bit-location is a numeric value specifying the bit that is to be set.

Bits are 0-based and are ordered according to the following scheme:

If the string-expression contains 8 bits, they are ordered:

7 6 5 4 3 2 1 0

If the string-expression contains 16 bits, they are ordered:

7 6 5 4 3 2 1 0 15 14 13 12 11 10 9 8

If the string-expression contains 24 bits, they are ordered:

7 6 5 4 3 2 1 0 15 14 13 12 11 10 9 8 23 22 21 20 19 18 17 16

An exception occurs if the program attempts to test a bit beyond the declared length of the string-expression.

Example:

A$ = “@7FA5@”
!
FOR I = 0 TO 15
Result = TESTBIT(A$,I,EXCP=9999)
Print “Bit”;I;”is”;Result
NEXT I