Text constants represent strings of characters which usually do not have a numeric value. A text constant is enclosed between two double quotes - the string "Hello" is a text constant. The five letters between the quotation marks are the actual string. The quotation marks are not actually part of the string but just indicate its beginning and end.
Space characters are allowed within a text string as well as any character except the ASCII 0 character. Special characters which do not appear on the keyboard may be entered by holding down the ALT key on the keyboard, typing the decimal ASCII code for the character and then releasing the ALT key. Refer to your computer manuals for more information on this technique. VTS will not directly accept characters with ASCII codes greater than 127.
One special character is the double quote character itself. To include it as a character in the string instead of using it as the beginning or ending character, you must use two consecutive double quote characters. For example, the characters " " " " represent a text constant which is one double quote character. The first quote marks the beginning of the string. The middle two quotes are the two consecutive quotes used to represent the one double quote character to be included in the string. The last quote marks the end of the string.
There is no limit on the number of characters in the text constant. A text constant may even contain no characters (""), in which case it is called a null string. The use of the single quote (') is not a legal substitute for the double quote (").
Some examples of text constants are:
"Feed conveyer malfunction"
"1232.55"
"""We lived for days on nothing but food and water."" W.C. Fields"
Note the use of double quotes within the last text constant example. Since variables and constants satisfy the definition of an expression, they are expressions in themselves.