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Output Statements
19
This section illustrates some of the more common uses of the PRINT USING statement. Appendix D contains a
more formal discussion of the details.
Numeric Format Fields
First consider a simple example of formatting numeric values:
PRINT USING “-###.###”: -Pi, 9^3
The format string “-###.###” causes the PRINT USING statement to print a numeric value with exactly three
decimal places, adding zeroes or rounding if necessary. It allows up to three places before the decimal point and
reserves a space for the sign if the value is negative. Leading zeroes will not be printed. Thus, the output for the
above statement would appear as:
- 3.142 729.000
You may define the format string within the PRINT USING statement, or you may define a string variable for
use with PRINT USING. The following two statements produce the same output as the example above:
LET format$ = “-###.###”
PRINT USING format$: -Pi, 9^3
In these examples, the format string contains only one field. A field is the format specification for a single print
item. Since there is only one field but two print items, the field is used twice — once for each print item. Notice that
each item uses eight spaces with no extra spaces separating the two print items. True BASIC follows the format
string precisely and adds no additional spaces regardless of data type or punctuation between print items. If you
want spaces to precede or follow each number you must include those spaces within the format string:
LET format$ = “ -###.### “
PRINT USING format$: -Pi, 9^3
The field length is the number of character positions that the value will occupy when printed. In the format string
“-###.###”, the field length is eight spaces, which includes the spaces reserved for the sign and the decimal point.
Numeric values are aligned with the decimal within a field (that is, they are printed decimal justified). This means
that if several numbers are printed with the same format string, one under the other, any decimal points (or commas)
will line up. If no decimal point is present in the field, numeric values are aligned with the right edge of the
field (right justified).
In the format string “-###.###”, the first position in the field is reserved for a negative sign; it may not be occupied
by a digit. Here are some examples; notice the last one in particular.
Examples of Output Formatted with the String: “-###.###”
——————————————————————————————————————
Number
Output
17 17.000
17.1234 17.123
-123.4687 -123.469
-17.2 - 17.200
12345 ********
——————————————————————————————————————
If a number cannot be printed in the specified format, asterisks are printed instead, as in the last example. The
field’s length determines the number of asterisks printed.
Format fields are composed of place holders. Place holders are characters that reserve space within the field for a
specific character or range of characters that may appear in the printed value. The format string “-###.###” contains
three different place holders: the minus sign (–), the pound sign (#), and the decimal point (.).
There are other place holders that you may use to compose fields in format strings. The following table summarizes
all the place-holder characters valid for numeric values: