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22 True BASIC Language System
When run, this program produces the unexpected output:
Answer 31 is
The reason for this output is quite simple: the pound sign before the digit 1 (intended to represent the number sign)
is interpreted as the first numeric field. Therefore, True BASIC rounds the value of 2.6 to 3 and prints it in this
field. Other characters, including the 1, are printed as constants. Since no second print item is available for the
second field (which we intended to be the only field), the format string is printed only to the first character in that
field.
Now consider the following potential solution:
PRINT “Answer #1 is “;
PRINT USING “##.#. Good job!”: 2.6
END
Since the problematic pound sign is no longer part of the PRINT USING statement, this form of the program
solves that part of the problem, but it also brings up another problem. When you try to run this program, you get
an error message claiming that you have a “Badly formed USING string.” This means there is now something illegal
in the format string.
This problem is a little trickier to find, but it makes sense. The second period (intended to end the first sentence)
is directly adjacent to the format field. Since it is a valid place holder, True BASIC considers it part of the field.
However, this results in a field with two decimal points which is not possible, so True BASIC generates the error.
(This error didn’t occur in the first example because True BASIC stopped using the string before it reached that
point.)
To fix this problem, modify the program as follows:
PRINT “Answer #1 is “;
PRINT USING “##.#”: 2.6;
PRINT “. Good job!”
END
When you run this version of the program it produces the output originally intended:
Answer #1 is 2.6. Good job!
Notice that a semicolon at the end of a PRINT USING statement has the same effect as at the end of a PRINT
statement.
String Format Fields
True BASIC also lets you format string values with the PRINT USING statement, but the options are more limited.
The PRINT USING statement with string values is most useful if you wish to define fixed length fields and
control the justification (alignment) of the string values within those fields.
You may print strings with any numeric format item. Unless you specify otherwise, True BASIC centers the string
within the field, adding spaces if needed. (If necessary, there will be one more space to the right than to the left.)
If the string is too long to fit the format field, asterisks are printed instead, just as with numbers.
You may also tell True BASIC to align a string to the left or right within the format field using two special string
place holders, “”:
String PRINT USING Place Holders
——————————————————————————————————————
Place Holder
Reserves Space For
# character or space
< character or space; left justifies string value in field
> character or space; right justifies string value in field
——————————————————————————————————————
In case of more than one “”, the left most one decides.