Text Strings

Text Strings

A "string" is a sequence of any valid ASCII character (of the decimal range of 0 to 127) enclosed by double quotes.

Strings may be of any length that will fit within a 255 column source line. If a matching quote mark is found, the string ends. If none is found before the end of the line, the string will end at the end of the line. While there is no direct provision for continuation onto a second line, it is generally no problem to use a second DW directive for the next line.

The DW directive will store the entire string into successive words. If a string has an odd number of characters (bytes), the DW and DATA directives will pad the end of the string with one byte of zero (00).

If a string is used as a literal operand, it must be exactly one character long, or an error will occur.

Code Examples

See the examples below for the object code generated by different statements involving strings.

7465 7374 696E dw "testing output string one\n"

6720 6F75 7470

7574 2073 7472

696E 6720 6F6E

650A

#define str "testing output string two"

B061 movlw "a"

7465 7374 696E data "testing first output string"

6720 6669 7273

7420 6F75 7470

7574 2073 7472

696E 6700

Escape Characters

The assembler accepts the ANSI `C' escape sequences to represent certain special control characters:

Table: ANSI `C' Escape Sequences

Escape Character	Description	Hex Value
\a	Bell (alert) character	07
\b	Backspace character	08
\f	Form feed character	0C
\n	New line character	0A
\r	Carriage return character	0D
\t	Horizontal tab character	09
\v	Vertical tab character	0B
\\	Backslash	5C
\?	Question mark character	3F
\'	Single quote (apostrophe)	27
\"	Double quote character	22
\0OO	Octal number (zero, Octal digit, Octal digit)
\xHH	Hexadecimal number