A function returning the value -1.

 10 flag=FALSE
100 IF answer$=correct$ flag=TRUE
150 IF flag PROC_got_it_right ELSE PROC_wrong

BBC BASIC (Z80) does not have true Boolean variables. Instead, numeric variables are used and their value is interpreted in a 'logical' manner. A value of 0 is interpreted as false and NOT FALSE (in other words, NOT 0 (= -1)) is interpreted as TRUE.

In practice, any value other than zero is considered TRUE. This can lead to confusion; see the keyword NOT for details.

See the Variables sub-section for more details on Boolean variables and the keyword AND for logical tests and their results.



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