If the case body contains a numbered statement list, then the statement list to be executed is selected in the following manner:
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The arithmetic expression in the case head is evaluated. If the resulting value is not an integer, it is integerized by rounding.
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If the integer value is equal to one of the statement numbers, the statement list associated with the number is executed.
If the integer value is not equal to any of the statement numbers, then an invalid index fault occurs unless the word ELSE appears in a number list in the CASE statement, in which case control is transferred to the statement list following ELSE.
The statement numbers given by the constant arithmetic expressions in the number list must lie in the range 0 to 1023, inclusive. The word ELSE can appear only once in a CASE statement.
