Word Processing BAR Code
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
This article describes a binary code useful for word processing applications and usable on impact and nonimpact printers. The code is insensitive to low-frequency velocity variations so that it can be scanned by hand or machine.
Word Processing BAR Code
This article describes a binary code useful for word processing applications and usable on impact and nonimpact printers. The code is insensitive to low- frequency velocity variations so that it can be scanned by hand or machine.
Certain terms used in this description are defined below.
BAR CODE: A binary encoding on printed media using two contrasting colors, usually black and white, containing information in one dimension only.
MODULE: The minimum dimension that can be specified for the code, defining the code resolution (in modules per unit distance).
BAR: One or more modules of the same color in a contiguous group.
MARK: A printed bar in the color of the ink.
SPACE: An unprinted bar in the color of the background (paper).
BIT CODES: Bar codes intended to be printed and decoded on a bit basis.
CHARACTER CODES: Bar codes intended to be printed and decoded using a fixed number of modules. (Character codes have the advantage that a printer can print them as it would any other character font.)
WIDTH DECODING: A decoding process measuring the relative widths of bars. (Systematic variations, such as marks that are consistently too wide, adversely affect the performance of width decoding.)
LIKE-TRANSITION DECODING: A decoding process measuring the widths of adjacent mark-space and space-mark pairs. Distances are always measured from a mark to a mark or from a space to a space, hence the designation like- transition.
The two most common classes, encompassing most of the codes defined to date, are binary bar width modulation codes (BBWM) and (N,K) codes.
BBWM codes are characterized by one or two bar widths and one or two space widths. BBWM codes are well suited to bit codes, but they have also been used for character codes. Depending upon the coding rule chosen, BBWM codes can be either width or like-transition decoded.
The other class of common bar codes, the (N,K) codes, are character codes. N is the number of modules in the character having K marks and K spaces. The (N,K) codes are like-transition decodable and so have good insensitivity to systematic variations. An example of an (N,K) code is the UPC (Universal Product Code) which is a (7,2) code, i.e., the UPC character is composed of 7 modules with two marks and two spaces.
The word processing bar code (WPBC) to be described has the
(1) The code is applicable to impact printers, e.g.,
daisy wheel, and nonimpact printers, e.g., ink
(2) The code is velocity independent so it is hand- or
(3) The bar code is bidirectionally readable, short
beginning and end sequences being used to provide
unique decodability independent from scan
(4) There are at least 63 unique code points for the
upper and lower case alphabetics, the decimal
numbers, and one escape code, with control and
special codes being encoded using the escape
(5) The average density (number of symbols per unit