lmayer@elgin.edu

8 - FOR loops and Arrays

For/Next loops:

Add integers from 1 to 100: p. 262

• 'loop using Do While ‘loop using For Next
• CLS ‘clear screen  CLS ‘clear screen
• Sum = 0  Sum = 0
• Count = 1  For Count = 1 to 100
• Do While Count <=0   Sum = Sum + Count
• Sum = Sum + Count Next Count
• Count = Count +1 Print "The Sum is "; Sum
• Loop
• Print "The Sum is "; Sum
• Sum  Count
• 0  1
• 1  2
• 3  3
• 6  4
• 10   5
• ...  ...
• 4950   100
• 5050   101
• Incrementing:
• If no Step is included, Step 1 is assumed
• Stepping by values other than 1 and initializing the loop variable to other than one
• 'Add all even integers
• CLS ' clear screen
• Sum = 0
• For Count = 2 to 100 Step 2
• Sum = Sum + Count
• Next Count
• Print " The Sum is "; Sum
• Sum  Count
• 0  2
• 2  4
• 6  6
• 12   8
• ...  ...
• 2350   100
• 2450   101
• Values for a For statement:
• Decimal: For Count = .5 to 10 Step .5

Variables in a For statement:

Sum = 0

Number = 20

Increment = 1

FOR 1 TO Number Step Increment

 Sum = Sum + Number

NEXT Number

• PRINT " The Sum is "; Sum

Expressions as values in a For statement:

For Y =  (A * B )/C to P* (F-G)  Step C*2

*note: an increment value of zero creates an infinite loop

• Exiting a For loop prematurely: p. 268
• ' Premature exit from a For loop
• ' *************************
• Total.Amount = 0
• FOR Loop.Variable = 1 to 5
• Input "Amount Value"; Amount
• IF  Amount <= 0 THEN
• PRINT  "Amount = <=0..... Program ending"
• END IF
• Total.Amount = Total. Amount + Amount
• NEXT Loop.Variable
• PRINT : PRINT “Value of Loop.Variable is”; Loop.Variable

Loop.Variable = 1  Total.Amount = 0

     2       23

     3       39

Number of Iterations for a FOR loop

= (limit - initial value)/ increment value +1

What happens in the following? p. 270

Count = 0

FOR I = 10 TO 1 STEP 2

 Count = Count + 1

NEXT I

PRINT| "The loop variable is equal to"; I

PRINT "The FOR loop is executed"; Count; "times"

What if the increment value is -2?

Nested FOR loops: page 271

'Generating the multiplication table

'*****************************

CLS 'clear screen

PRINT " x !  0   1   2   3   4   5   6   7   8   9   10  11   12"

PRINT "---------------------------------------------------------"

FOR Row = 0 TO 12

 PRINT USING "####"; Row ;

 FOR Column = 0 to 12

  PRINT USING "####"; Row * Column

 NEXT Column

 PRINT 'move to next line

NEXT ROW

PRINT  'move to next line

Invalid nesting of FOR loops:

FOR A = 1 TO 10

     do stuff

     FOR B = 1 TO 10

             Do other stuff

Next A

     Next B