programming-for-dummies

210
Playing with Nested Loops
The following shows a FOR-NEXT loop nested inside another FOR-NEXT
loop, as shown in Figure 5-3:
FOR I = 1 TO 4
PRINT “Outer loop run #”; I
FOR J = 1 TO 3
PRINT “
NEXT J
NEXT I
Nested loop run #”; J
FOR I = 1 TO 4
PRINT “Outer loop run #”; I
Figure 5-3:
A nested
loop
appears
inside
another
loop.
Outer loop
Nested loop
FOR J = 1 TO 3
PRINT “ Nested loop run#”; J
NEXT J
NEXT I
When one loop is nested inside another loop, the inner (nested) loop runs
first. Then the outer loop runs once. Then the outer loop repeats running the
nested loop again.
With nested loops, the nested (inner) loop runs more often than the outer
loop.
In the preceding example, the outer loop runs 4 times and the nested loop
runs 3 times, so the nested loop ultimately runs 12 times (3 * 4), as shown
here:
Outer loop run #1
Nested loop run #1
Nested loop run #2
Nested loop run #3
Outer loop run #2
Nested loop run #1
Nested loop run #2
Nested loop run #3
Outer loop run #3
Nested loop run #1
Nested loop run #2
Nested loop run #3