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Printing BAR Code on Dot Matrix Printer Using Programmable Symbols

IP.com Disclosure Number: IPCOM000035341D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 16K

Publishing Venue

IBM

Related People

Barcomb, JG: AUTHOR [+3]

Abstract

Disclosed is a method of determining that minimum set of symbols, representing valid segments of bar code, needed to permit program assembly of application-required bar code in a succession of character cells, which is downloaded to printer storage for printing.

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This is the abbreviated version, containing approximately 47% of the total text.

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Printing BAR Code on Dot Matrix Printer Using Programmable Symbols

Disclosed is a method of determining that minimum set of symbols, representing valid segments of bar code, needed to permit program assembly of application-required bar code in a succession of character cells, which is downloaded to printer storage for printing.

Assume one wants to produce "3 of 9" bar code on a printer capable of printing dots at 90 or 180 dots per inch horizontally, with dot diameters of .018 and .016, respectively. The bar code is composed of narrow and wide bar and space elements with a narrow to wide element ratio of approximately 3. The printer requires character cell definition of 8 dots vertically and either 9 dots horizontally, if printing 90 dots per inch, or 12 dots horizontally, if printing 180 dots per inch.

From the above, it is possible to derive, for 90 dots per inch, the dot definition of the bar code elements to achieve the required ratio: NARROW BAR = 1 NARROW SPACE = 00 WIDE BAR = 1111 WIDE SPACE = 00000 in which 1 is a dot and 0 is an equivalent space.

Now, since "3 of 9" bar code characters consist of nine elements, three of which must be wide elements, and since the first and last elements must be bars, and since bar and space elements alternate, it necessarily follows that each bar code character requires twenty-two (22) printer dot spaces. Assuming left-hand justification in the first cell, this is two full printer character cells plus four dot spaces of a third cell. (The remainder of the third cell provides intercharacter white space.) Since the printer character cell is nine dots wide, it is apparent that for some bar code characters the multiplicity of dots or spaces required for some individual elements may overflow from one cell to the next. If the contents of each of the three successive printer character cells is considered to be a symbol, it follows that any desired bar code character can be produced by program selection of the correct sequence of three symbols from a table containing all required symbols. It must be noted that the left-hand symbol must start with a bar, and the right-hand symbol must contain only four significant dot spaces and end with a bar. In addition, the "0's" or "1's" on opposing sides of the junctions of the middle cell and each of its two neighbors must be complementary and form a complete bar or space.

To determine the set of symbols required, consider that if the nine dot spaces of a character cell, each of which may contain a "0" or a "1", are treated as three binary numbers of three positions each (which can be interpreted as octal numbers), it follows that there are 512 (2 to the 9th power) possible combinations. It also is apparent that, considering the bar and space definitions, and the conditions noted above, not all 512 combinations form valid symbols.

Since each 9-element character must start with a bar and end with a bar, and since bars and spaces alternate, it follows that all...