"Bar Code Loader"
By Ken Budnick
Copyright 1977
ISBN: 0-07-008856-X


Description from Back Cover of "Bar Code Loader"
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PAPERBYTE - An Exciting New Way To Distribute Software
 
One of the most common problems for users and suppliers of personal computer 
software is the need for product distribution in a form which is helpful to the 
user, low in cost, tolerant of errors in production use, and free of the need 
for expensive highly specialized peripherals.  One solution, conceived in 
detail by Walter Banks of the Computer Communications Network Group at the 
University of Waterloo, Ontario, Canada, is the use of bar code patterns 
prepared on a computer controlled phototype-setter.  A bar code is a linear 
array of printed bars of varying width which encodes digital data as 
alternating patterns of black ink and white paper. By using a ruler as a guide, 
an inexpensive hand held "wand" scanning unit converts the bar patterns into a 
time varying logic level signal.  This time varying binary value can then be 
interpreted by a program which understands the format of the bars.
 
The purpose of this pamphlet is to present the decoding algorithm which was 
designed by Ken Budnick of Micro-Scan Associates at the request of BYTE 
Publications Inc.  The text of this pamphlet was written by Ken, and contains 
the general algorithm description in flow chart form plus detailed assemblies 
of program code for 6800, 6502 and 8080 processors.  Individuals with computers 
based on these processors can use the software directly.  Individuals with 
other processors can use the provided functional specifications and detail 
examples to create equivalent programs.



Table of Contents
-----------------

Byte Publications and PAPERBYTE Software
The Bar Code
Loader Design Considerations
A General Bar Code Loader Algorithm
     LDA or LDR Subroutine
     RBYT Subroutine
     RBIT Subroutine
     RBAR Subroutine
Adjusting Program Timing Loops
The 6800 Bar Code Loader Program
The 6502 Bar Code Loader Program
The 8080 or Z-80 Bar Code Loader Program
Using The Bar Code Loader Algorithm
     Implementation and Checkout Procedure Text Entry Procedure
     Absolute Entry Procedure
     A Note About Bar Codes



BYTE Publications and Paperbyte (TM) Software
---------------------------------------------

Notes by Carl Helmers, Editor in Chief

     The bar code format presented here was conceived as a result of a 
telephone conversation between Walter Banks and myself in August of 1976.  This 
conversation led to Walter's presentation on bar code technology at the 
Personal Computing '76 show in Atlantic City NJ in August 1976.  It was Walter 
who came up with a practical way to implement printed software, a prospect 
which had been a relatively low priority "wouldn't it be neat if we had a way . 
. ." kind of idea in our minds before we met.

     Our intent is to promote a method for recording machine readable printed 
software that would be both easy to use and publicly available for software 
product distribution.  We have no intentions of restricting the use of this 
kind of notation in any way.  We believe that its relationship to the personal 
computer software industry parallels that of written music notation to the 
music industry: no one company, individual or organization has any specific 
proprietary claim to the notation itself; rather it is the intellectual 
property expressed by music notation which is produced and distributed by 
composers and music publishing companies.  (The legal and ethical comparisons 
between the software publishing and music industries do not stop at this one 
point.)

     As a firm, BYTE Publications Inc does formally claim trademark on our 
"brand name" of Paperbytes (TM).  I feel that BYTE magazine's articles and 
software books that use bar code machine readable text have a distinctive 
quality of style and technical excellence which sets them apart from the 
ordinary.  This pamphlet serves as but one example of our product, the kind of 
technical documentation and information which is needed by individuals 
experimenting with the personal use of computers.

     Our purpose as a book production company is to make high quality technical 
documentation of software products available to personal computer 
experimenters.  Mass production allows us to make these products available at 
relatively low prices when compared with the cost of similar software items in 
the recent history of the computing industry. Our  Paperbytes (TM) assemblers, 
compilers, interpreters, operating systems and applications programs come 
complete with source code listings, relevant object code listings, and machine 
readable bar code format.  Paperbytes (TM) provides a means by which software 
artists can earn royalties from their creations by making them available to a 
larger number of people, thereby benefiting both the author and the computing 
public.  I see this as a technological turning point in the history of computer 
software.

Carl Helmers
BYTE Publications Inc August 15, 1977