If

IF Statement

if condition then statement

Applications use selection statements to choose among alternative courses of action.

For example, suppose that the passing grade on an exam is 60. The BR statement below determines whether the condition grade >= 60 is true or false. If the condition is true, "Passed" is displayed, and the next BR statement in order is performed. If the condition is false, the output statement is ignored, and the next BR statement in order is performed.

00010 print "Enter a grade"
00020 input grade
00030 if grade >= 60 then print "Passed"
00040 stop

Multi-line IF Statements

The same program could be rewritten to put the print "Passed" statement on a separate line with indentation to emphasize that this statement may or may not happen:

00010 print "Enter a grade"
00020 input grade
00030 if grade >= 60 then 
00040    print "Passed"
00050 end if
00060 stop

In the above example, end if marks the end of the statements which will be performed if the grade >= 60 condition is true. The indentation of line 40 of this selection statement is optional, but recommended, because it emphasizes the inherent structure of the if statement.

Programmers often run into situations in which more than one statement needs to be executed if a particular condition is true. To illustrate the method of achieving this in BR, we will expand the above example to print multiple statements if the grade entered by the user is more than or equal to 60:

00010 print "Enter a grade"
00020 input grade
00030 if grade >= 60 then 
00040    print "Passed"
00050    print "You will not need to re-take the test" 
00060    print "Good job"
00070 end if
00080 stop

IF... ELSE Statement

When your programming needs call for two different actions depending on whether or not a condition is true, the IF... ELSE statement should be used.

00010 print "Enter a grade"
00020 input grade
00030 if grade >= 60 then 
00040    print "Passed"
00050 else
00060    print "Failed"
00070 end if
00080 stop

IF... ELSE IF Statement

When your programming needs call for many different actions depending on multiple conditions, the IF... ELSE IF statement should be used.

00010 print "Enter a grade"
00020 input grade
00030 if grade >= 90 AND grade <= 100 then 
00040    print "Got an A"
00050 else if grade >= 80 AND grade <= 89 then 
00060    print "Got a B"
00070 else if grade >= 70 AND grade <= 79 then 
00080    print "Got a C"
00090 else if grade >= 60 AND grade <= 69 then
00100    print "Got a D"
00110 else if grade < 60 AND grade > 0 then
00120    print "Failed"
00130 end if
00140 stop

IF... ELSE IF... ELSE Statement

The program above covers all scenarios except two:

1. When the grade entered by the user is negative 2. When the grade entered by the user is greater than 100

In order to catch this problem, you may add an ELSE clause to the end of the program above, resulting in:

00010 print "Enter a grade"
00020 input grade
00030 if grade >= 90 AND grade <= 100 then 
00040    print "Got an A"
00050 else if grade >= 80 AND grade <= 89 then 
00060    print "Got a B"
00070 else if grade >= 70 AND grade <= 79 then 
00080    print "Got a C"
00090 else if grade >= 60 AND grade <= 69 then
00100    print "Got a D"
00110 else if grade < 60 AND grade > 0 then
00120    print "Failed"
00130 else
00140    print "Invalid grade. Must be positive and less than 100"
00150 end if
00160 stop

Complex Conditions

Category:Operations#Logical_Operations