Bronze Edition Guide - True BASIC

38 BRONZE Edition Guide
Notice the variable total. In the fourth line, an arithmetic expression assigns a value to total
(the sum of the three items, or 1476 in this case):
LET total = item1 + item2 + item3
The next line uses that value of total with the constant .04 to compute the value of tax (.04
* 1476 = 59.04). Now examine the next statement:
LET total = total + tax
This statement assigns a new value to total by adding the previous value of total (1476) to
the value of tax (59.04). After this statement, total has this new value (1535.04), and thus
the PRINT statement uses that value when you run the program.
You could rewrite the COST program to use a separate variable (such as itemtotal or subtotal)
for the intermediate total. Indeed, using two different variables may often be the wisest
choice. However, this ability to add to the value of a variable is important as you’ll see
when you begin to use loops in your programs (see Chapter 8).
An Introduction to Strings
True BASIC processes words as well as numbers. In computer terminology, anything that
doesn’t have a numeric value is called a string. Your age is a number, but your name or
street address is a string. Strings can include any character your computer can display.
Like numbers, strings can be constants, variables, or expressions.
In the Chapter 5, you used strings with PRINT statements to tell the user what to enter for
the INPUT statements in your MPG2 program:
! Compute miles per gallon
!
PRINT “How many miles”;
INPUT miles
PRINT “How many gallons”;
INPUT gallons
PRINT miles, gallons, miles/gallons
END
Another common use of strings in computer programs is to print text with the output, to
make it clear what the numbers mean. You could add another PRINT statement near the
end of the above program:
. . .
PRINT “Miles”, “Gallons”, “Miles per Gallon”
PRINT miles, gallons, miles/gallon
END