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Looping and Decision Making
 
The following programming examples illustrate how to code loops and
decision-making program structures.
 
Example 1
 
The following examples illustrate the similarities and differences
between the SELECT CASE and IF...THEN...ELSE statements.
 
Here is an example of using block IF...THEN...ELSE for a multiple-choice
decision:
 
  INPUT X
  IF X = 1 THEN
    PRINT "one"
  ELSEIF X = 2 THEN
    PRINT "two"
  ELSEIF X = 3 THEN
    PRINT "three"
  ELSE
    PRINT "must be integer from 1-3"
  END IF
 
The above decision is rewritten using SELECT CASE below:
 
  INPUT X
  SELECT CASE X
    CASE 1
      PRINT "one"
    CASE 2
      PRINT "two"
    CASE 3
      PRINT "three"
    CASE ELSE
      PRINT "must be integer from 1-3"
  END SELECT
 
The following decision can be made with either SELECT CASE or
the block IF...THEN...ELSE statement. The comparison is more
efficient with the block IF...THEN...ELSE statement because
different expressions are being evaluated in the IF and ELSEIF
clauses.
 
  INPUT X, Y
  IF X = 0 AND Y = 0 THEN
    PRINT "both zero."
  ELSEIF X = 0 THEN
    PRINT "only X is zero."
  ELSEIF Y = 0 THEN
    PRINT "only Y is zero."
  ELSE
    PRINT "neither is zero."
  END IF