Category: Character Literals

A character literal is any string of characters enclosed in quotation marks as shown in the following example:
‘This is a character string.’
“This is a character string, too.”
For convenience, you can enter character literals without the delimiting quotation marks; however, quotation marks are required in some situations. The rules for using quotation marks are described in Quotation Marks.
Valid and Invalid Literals
The following are examples of valid literals:
‘abc’
Is a character string.
‘ab”C’
Is a character string.
”
Is a null string.
3.14159
Is a number literal.
9
Is a number literal.
‘10.99’
Is a character string.
‘John\’s toy boat’
Is a character string.
‘ABCd_EfG’
Is a character string.
‘1234A’
Is a character string.
The following are examples of invalid literals:
1 23
Spaces are not permitted in number literals.
$10.99
Periods are not permitted in an unquoted character string, and the dollar sign is not permitted in a number literal.
‘John’s toy boat’
‘John’ is a valid character string, but the rest of the line is invalid.

A null string is a character string of zero length. Unlike the $Null property that indicates that the value is unknown or unassigned, the null string is a known value.

For example, if you have two variables, x and y, both of which are null strings, then the expression

x = ” and y <> ‘abc’

is logically true.

Certain characters, such as quotation marks and the backslash, have special functions in the software. If you need to use one of these metacharacters as a literal character in a string, you must “escape” the special function by inserting a backslash ( – Escape) preceding the metacharacter as shown in the following example:

‘This is a quotation mark (‘).’
‘This is a backslash (\).’

Any character string containing a metacharacter used as a literal must be enclosed in quotation marks.

If you need a place a character not normally available from the keyboard into a character literal, use the backslash to create the hex code for that character as shown in the following example:

‘This string has an ASCII escape generated by hex 1B (1B)’

The two characters immediately following a quoted backslash are treated as hex code provided they are either digits from 0 to 9 or letters from A (a) to F (f).

Any character string containing a hex code must be enclosed in quotation marks.

Note: The escape function of the backslash inside quoted character strings can be switched off with a SET ESCAPECHAR command.

Example

Character literals that include hex codes can be useful for sending control codes to printers and terminals. For example, if the ASCII codes SI (hex 0F) and DC2 (hex 12) are used, respectively, to select and cancel condensed printing on your particular printer, use the following sequence of statements to print a report in the condensed mode:

set output printer   % switch serial output to printer
output ‘F’;        % switch condensed print on
…. commands to generate report ….
output ’12’         % switch condensed print off
set output terminal  % switch output back to terminal

A character literal is any string of characters enclosed in quotation marks as shown in the following example:

'This is a character string.'
"This is a character string, too."

For convenience, you can enter character literals without the delimiting quotation marks; however, quotation marks are required in some situations. The rules for using quotation marks are described in Quotation Marks.

Valid and Invalid Literals

The following are examples of valid literals:

The following are examples of invalid literals: