Scope of DO Variables

Fortran 90 is not block structured, all DO variables are visible after the loop and have a specific value. The index variable is recalculated at the top of the loop and then compared with < expr2 >, if the loop has finished, execution jumps to the statement after the corresponding END DO. The loop is executed three times and i is assigned to 4 times, the index variable will retain the value that it had just been assigned. For example,

    DO i = 4, 45, 17
     PRINT*, "I in loop = ",i
    END DO
    PRINT*, "I after loop = ",i

will produce

    I in loop =  4
    I in loop =  21
    I in loop =  38
    I after loop =  55

Elsewhere in program the index variable may be used freely but in the loop it can only be referenced and must not have its value changed.

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