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Proportional Spacing Print Point Calculation Without Line Memory

IP.com Disclosure Number: IPCOM000047083D
Original Publication Date: 1983-Sep-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 6 page(s) / 50K

Publishing Venue

IBM

Related People

Booth, JR: AUTHOR [+2]

Abstract

When printing in proportional spacing mode, the escapement required to move from print point to print point is one half of the immediately preceding character escapement plus one half of the new character escapement. In printing systems that erase, a memory that remembers the previous character is required to correctly compute the escapement distances required for erasure, if the above equation is to be applied directly. The operation described below may be employed to compute the required escapement distances for printing and erasing without utilizing line memory. At the outset it is desirable to define the various types of discrete escapement operations. These types may be classified as "go to" (new line), "tab" (tab and backspace), and "graphic" (print and/or erase).

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Proportional Spacing Print Point Calculation Without Line Memory

When printing in proportional spacing mode, the escapement required to move from print point to print point is one half of the immediately preceding character escapement plus one half of the new character escapement. In printing systems that erase, a memory that remembers the previous character is required to correctly compute the escapement distances required for erasure, if the above equation is to be applied directly. The operation described below may be employed to compute the required escapement distances for printing and erasing without utilizing line memory. At the outset it is desirable to define the various types of discrete escapement operations. These types may be classified as "go to" (new line), "tab" (tab and backspace), and "graphic" (print and/or erase). Each of these escapement types may be processed by a separate white space accumulator operation to produce the net escapement of the carrier of the printer. The white space accumulator operation uses two variables, the carrier position and the present "hammer position", to perform a calculation. The carrier position is defined as the leading edge of the next carrier character box, while the present hammer position is defined as the present location of the print hammer. The operator's cursor is assumed to be pointing into the next character box. In the subsequent discussion, the printer is assumed to escape and then print. (Impact printers may be classified into those which print a character and then escape and await an order to print another character, or printers that escape first and print only after receipt of a character to be printed signal.) The computational process performed for the three types of escapements defined above are accomplished in any convenient microprocessor (processor) implementation which allocates some portion of its read-only memory (ROM) and random-access memory (RAM) (registers and the like) for analyzing and computing the escapement types set forth above. The actual performance algorithms employed by the computational process are as follows: The "go to" escapement computational processes include: 1. Net escapement (new) = net escapement (old) + destination (new) - carrier position (old) 2.

Present hammer (new) = present hammer (old) + destination (new) - carrier position (old) 3. Carrier position (new) = absolute destination (new) The "tab" escapement computations or algorithms may be set forth as follows: 1. Net escapement (new) = net escapement (old) + displacement (relative displacement) 2. Present hammer (new) = present hammer (old) + displacement 3. Carrier position (new) = carrier position (old) + displacement The "graphic" escapement algorithms are set forth as follows, assuming that the "next hammer" is a temporary variable in the process. 1. Next hammer (new) = carrier position (old) + (graphic escapement/2) 2. Net escapement (new) = net escapement (old) + next

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