CA1118702A - Underscore erase - Google Patents

Abstract

UNDERSCORE ERASE

Abstract of the Invention The electronic controls for a typewriter disclosed herein allow the operator to erase a character using automatic erase capability such as disclosed in U. S. Patent 3,780,846 and at the same time to remove any underscores associated with that character. When an underscore command is entered the memory which stores the code representing the characters typed is caused to be altered in its content to indicate upon the reading of that code segment that the character has been underscored and that the character must be erased along with the underscore. The apparatus accomplishes multiple erase cycles to remove the underscore and then the character. In proportional space mode of operation it is possible that multiple underscore erase cycles will be necessary to remove an underscore which is wider than the underscore type font on the type element.

Description

37~

l UNDERSCORE ERASE
This invention relates in general to typewriters and more speci-fically to means for erasing errors in a typing line where the type-writer is provided with proportional spacing capabil-ity.
In order to accomplish the correction of information on a typing line in a typewriter where an error has been made and where the in-Formation to be corrected has been underscored, it is necessary to remove both the underscore and the character which is being corrected.
This is particularly necessary in the situation where erasure is effect~
ed automatically upon the depression of the correction key on the type-writer keyboard since in this mode of operation it is possible to remove all characters in reverse order back to the erroneous character. The need for the removal of the underscore as well as the character is further necessitated because, in a typewriter having proportional space capability, the character inserted in place of the corrected character may not have the same width or escapement value and therefore, the underscore may not correspond to the word or line length as is desirable.
When an electronic memory is included into the typewriter for its operation and control, it is also advantageous to utilize an automatic erasing arrangement similar to that disclosed in U.S. Patent No. 3,780,~46 to Robert Kolpek et al, commonly assigned herewith.
SUMMARY OF TH~ INVENTION
The improvement over the techniques which are capable with such products as the IBM* Memory Typewriter comes in that the electronic controls will automatically reposition the print carrier oF the typewriter, erase the underscore and then erase the character upon depression of the erase control key. In the event that the underscore does not correspond to the full width of a wide character such as a capital "W" or capital "M" in the proportional space mode of operation, the electron1c controls reposition the carrier for a second underscore *IBM is the registered trade mark of International Business Machines Corporation.
LE9-77-016 -l-)2 erase functlon to fully remove the underscore which has been applied under that letter.

In an underscore erase operation, the under~core beneath the character is first erased and then the character is removed by a second error S correction cycle of the typewrlter. The inormation as to the presence of an underscore is determined by checking one of the binary bits stored in memory representing the character on the typing line. Since all the bits in an eight blt byte are not utilized in the coding of the alphanumeric characters as they are coded from the electrical contact~
on the typewriter keyboard and as processed by the processor, the eighth bit which is normally on or represented by a 1 is changed upon the underscoring of a character to an off or zero condition to indlcate that that particul~r character has been Imderscored. This blt is changed ln memory so that an error correction or erase command ls received and the character is read from memory for utilization in the error correction operation the eighth bit is sensed as a zero to indicate that that character has been underscored and thereby initiates an underscore erase routine in the typewriter to accomplish removal of the underscore.

Objects of the Invention .

It is an ob~ect of this invention to remove the underscore and the charac~er from a typed page in response to a single erase operation keyboard command.

It is another object of this invention to revmoe the underscore fro~ a composite character and the character regardless of character and underscore width.
If is a further object of this invention to de~ect the presence of an underscore under a character and to remove it when commanded to remove the çharacter.

Description of the Drawing FIG. 1 illustrates the electronics in b:Lock diagram ~orm ~hich is capable of controlling the printer to accomplish underscore erase.

FIG. 2 lllustrates the pri.nter wlth ~he electronic inputs and ou~puts which interface with the electronics of FIG. l.

FIGS. 3 through 7 are flow diagrams of the logic flows performed by the logic represented in block diagram for in FIG. l.

FIG. 8 is a diagram showing the interrelations of r~gisters and accumu-lators which manipulate the data within the logic and which utilizes the code contained in Appendlxes A through D.

A more complete understanding of the invention will be h~d from a reading of the detailed description to follow.

Detailed Description of the Invention Referring to FIG. l, there is illustrated a typewriter lO which is controlled by electronics in that the keyboard signals generated are processed electronically and the electronic controls therein then issue electronic commands to the printer to effect the appropriate functions of the printer elements to cause printing, escaping, backspacing, tabultion~ correction and other normal printer functions~
When a key lever on the keyboard 12 is depressed to effect the : selection of a character for printing, the keyboard apparatus 12 causes the switches to close in a predetermined pattern thereby transmitting signals from the keyboard 14 to the keyboard control unit l&. The keyboard control unit 16 captures the electronic inputs from the bail codes Bl through B7 and generates an appropriate strobe or control signal which then causes the total data signals to be transmitted to the character and velocity decode logic 18. The character and velocity decode logic 18 thel1 converts the signals from the keyboard control ~mit 16 i~o 3t~Z

signals which represent ~he posltion on ~he type element of the character selected by the key lever depresslon. Thls is accomplished by converting the keyboard control unit 16 slgnal into inpue signals to magnet drivers 30 which then efEect the rotation and the tilt of a single type element 15 or other conventional selection technlque, to position the type font desired at the print point and then the select;lun of other controls; such as the velocity with which that type font is propelled toward the printed page.

The keyboard control unit signals 16 are simult~meously read Lnto the escapement logic 22 which then through a conventional table look up determines the assigned escapement va].ues for each of the ch~racters which are represented by the output of the keyboard control unit 16.
These escapement values or width may be a standard width such as for example using a l/60th of an inch per unit, 6 units for a 10 pitch escapement or 5 units for a 12 pitch escapement. Addicionally with the escapement of characters being defined as units of l/60th of an inch, it is possible to assign escapement values to characters proportional to their actual printing width, otherwise known as proportionally spaced characters. This thereby provides the capability of escaping the typewriter responsive to the keyboard control signals and effecting - proportionally spaced character printingO

The position of the carrier or the print point of the typewriter is constantly stored in the escapement register 24 which is a portion o~
the escapement logic 22, thereby provlding a current location, measured from the left most point of travel of the carrier 17, and this value ls constantly being updated as the carrier 17 translates left or right under the control of any of the keyboard signals. The escapement logic 22 outputs the width of the characters which have been selected at the keyboard 12 to the escapement counter 36. This is necessary to provide a control over the escape~ent functlons of ~he printer. The escape~en~
counter 36 then stores on a temporary basis the information necessaxy to contr-l the translation of the print carrler 17 over a predeter~lne~

or preselected dis~ance. The escapemen~ colmter 26 ls controlled in lts operatlon by the signals emanatirlg from the integrator 2~ which has signals going into it representing the ou~put o~ the pitch l9 selection switch and the photoemitter/sensor 21 associated with the lead screw 23 and the escapement sLgnal wheel 25 which indicates the portion of a complete rotation through which the lead screw 23 has been rotated. The pulses created by the photoemitter/sensor 21 arrangemen~
on the end of the rotatable lead screw 23 of the typewriter 10 effect the decrementing of the escapement counter 36. A4 long as the escapement counter 36 contains a numerical value, the photoemitter/sensor 21 wl~
then pulse the escapement counter 26, through the :Lntegrator 28, and cause ~he escapement counter 36 to provide an O~ltpUt signal to the appropriate magnet drivers 30 to cause movement of the print carriage.

The escapement or movement of the print carriage ls a result of clutches 31 activated by signals emanating from the magnet drivers 30 which are provided their input from the escapement counter 36. The escapement signal, the direction signal, the drive signal and the erase signal all may emanate from the magnet drivers 30 which are controlled ultimately from the main keyboard 14. The escapement magnet driver 30 causes the release of the lead screw 23 and thus allows its rotation together with the emitter wheel 25 which interacts with the photoemitter/sensor 21 thus creating the signals discussed above. The direction magnet driver controls the engagement of the clutches 31 in the drive unit to determine the forward or reverse direction of the carrier, by controlling the rotational direction of the lead screw. The direction magnet driver provides the engagement or the coupling between the main drive motor 33 of the typewriter 10 and the lead screw 23, through the power tranfi~ission apparatus 35 or drive module.

The erase magnet driver 30 controls the elevation of the erase tape from the withdrawn position so that any subsequent printing effected by the print element 15 causes the impacting of the erase media agains, the pag~ to effect erasure, if the character being impacted was the same 7~)~

character as ~Jas previous:Ly impacted onto the printing ribbon at Lhat print point.

The printer control unlt 41 contains the character ve:Locity decode logic 18, the escapement logic 22, the escapement register 24 and the escapement counter 36, and the line memory 34. AB signals are decoded by the character and velocity decode logic 18 for subsequent util-l~atlon by the magnet drivers 20 for selection, that same information is temporarily stored in a memory designated as the line memory 34. Th's memory register is capable of receiving the storable data and placing it into the line memory 34 in the sequence in which Lt has been received, The line memory 34 is capable of being read in reverse tc determine characters which have been previously prln~ed and machine functions which have occurred during that particular line of operation, such as the underscoring or space command.

Functions of the typewriter are controlled by the function portion 26 of the keyboard 12. The functions which may be included into such a typewriter include underscore, tabulation, space, carrier return, shift and index. 0f particular interest in this case is the underscore function. The underscore command is sent from the keyboard 12 as a series of electronic signals emanating from the swltches 13 contained in the keyboard to the function decode logic 38. The function decode logic 38 determdnes which signal has been received and then pas~es t`nat function decode logic output into the escapement logic 22. The escapement logic 22 receives the decoded function signals and determines Z5 whether any escapement function is involved.

In the case of ~ord underscore, the characters are already stored in memory when the underscore command is keyboarded. This is due to the fact that the underscore command is keyboarded after the last character which the operator desires to underscore has been inserted, by way of the keyboard 12, into the printer 10 and the control logic.
Although the actual underscore command follows the text to be underscored . .

z in cases involving line underscore where more than one word and ~he intervening spaces are underscored, the keyboard 10 has been manipulated at the begimling of the underscora~le text to indicate tha~
that is the starting point for any subsequent line ~nderscore co~mand.
This is accomplished by depressing the alternate ~unction key or code key and a predetermined and designated alphanumeric key on the keyboard 12. Then the text to be underscored is typed and followed by the line underscore command. As a result of the line underscore command, the memory is searched for the "start o~ underscore" code or alternatively if the word underscore is the underscore command the memory 34 is searched for the next preceding space or tab which has been recorded into memory 34. During this reverse search operation for one of the codes which indicates a starting point for the underscoring, the eighth bit of each of the recorded characters, nu~.erals or spaces, collectively referred to as graphics, is converted to a 3ero from the normal one condition. With the eighth bit of the code bei.g turned off or converted to a zero, this will indicate on any subsequen, functions where underscoring is partially or totally determinative, that the graphic has been underscored. Upon the finding of the start underscore, either recorded as a result of the line underscore com~and or upon the finding of the space or tab function referred to above, the graphics accumulated between the point of the entry of the underscore command and ehe start underscore code is then utilized to determine the distance through which the carrier 15 of the printer 10 must reverse escape. With this distance determined and entered into the escapemert logic 22, and par~icularly the escapement counter 36, the printer is then caused to reverse tabulate or reverse escape to the start under-score position. The escapement register 24 has that location stored therein and the carrier 17 reposltions itself over the start of underscore location.

As this point the underscore logic 46 will then command the escapement logic 22 to cause appropriate escapements and the character and velocity decode logic 1~ to command the printing of underscores until the c~rrier '7~2 has returned to the position at which the underscore command was entered. The position at which the underscore command was entered ls stored in the line memory and the escapement lo~lc Z2 compares the carrier location, under the control of the underscore logic ~6 with ~he position recorded in line memory. As long as that position is more than one underscore width d-lstance from the print carrier posltion~ another underscore function operation will be accomplished the underscore printed together with the appropriate escapement until the point at which the underscore command was entered is reached by the carrier.
When an underscore operations ls initiated the first character to be underscored may not be an integral number of underscore lengths rom the end point of the underscore. If that is the case, the underscore logic escapes the carrier an amount after the fi~st underscore print to ali~n the carrier an integral number of underscore lengths from the end of underscore location. This will cause a small overlap between the first and second underscore print marks but will accomplish the alignment on the last underscore character. This particular sequence i5 neces3ary where the text to be underscored has been printed in a proportional spacing mode of operation where each character may vary in width an~
~0 escapement value. The realignment of the carrier for the last impact of underscore is not hecessary where the apparatus is being operated in a uniform pitch mode such as 10 or 12 pitch operation.

Character Erase If it is desired to return the carrier to some point in the line and erase a character which has been underscored, it being inmaterial whether it be the immediately preceding character or one earlier in the line where all characters are to be remo~ed back to the erroneo~s character, the erase command is accomplished by the depression of the erase key on the typewriter 10. When the erase key on the typewriter keyboard is depressed a signal emanates from the special function portion 26 of the keyboard 10 to the function decode logic 38. The function decode logic 38 then determines that an erase function has LE9~77-016 :

.. . . . . . ..

.9_ been keyed. The outputs from the functlon declode logic 38 are fed into the escapement logic 22 which causes the line memory 34 to be read in reverse order to determine the escapement value necessary to reposition the printer rarriage over the appropriate print point ~or correction. At the time that the line memory 34 is read to determ:Lne the character and therefore the escapement value, the escapement logic 22 detect~ the eighth bit condition belng a æero or off condition.
This causes the escapement logic 22 to divert control to the erase underscore logic 42. The erase underscore logic 42 then issues a series of electronic commands through the escapement logic 22 to cause the print element 15 and print carrler 13 ~o reverse escape to position the carrier 13 over the print position occupied by the character to be removed. This is accomplished by loading the escapement counter 36 with the number of escapement increments corresponding to that character width and the escapement counter 36 then commanding the magnet drive s 30 for escapement magnet, direction magnet and the drive magnet, to reposition the carrier in the reverse direction the requisite number of escapement increments. At the same time the escapement register 24 ls loaded with the position of the new print point. The erase underscore logic 42 commands the character and velocity decode logic 18 to effect a selection of an underscore and to effect the printlng of the underscore. This is accomplished by directlng, to the magn~t drivers 20, the appropriate rotate codes and velocity signals to effect the printing of the underscore. At the same time, as a result of the erase underscore logic 42 having controlled the escapement logic 22 ~nd the escapement counter 36, the erase magnet has been turned on to effect the positioning of the correction or erase tape 37 between the print element 15 and the printed page. Thus when the underscore is printed, it effects the erasure of the underscore. The erase underscore logic 42 control routine then causes the reading of the line memory 34 by the character and velocity decode logic 1~ and the decoding of the character code stored in the line memory 34 to effect a second selection using rotate, tilt and velocity codes and the turning on of the appropriate magnet drivers 20 to effect the '7~)~

the rotation and tilt of the type elemen~. The er~se underscore logic 42 also command the escapement logic 22 and the escapement counter 36 to inhibit escapement on the next cycle but to turn on the magnet driver 30 effecting the raislng of the erase tape 37. Thus upon the next machine cycle initiated by the escape underscore logic 42, this being the second complete machine cycle opera~ed at the same print point, the character is then selected and the erase med-la 37 positioned between the print element 15 and the prlnt point on the paper thus affecting erasure of the character.

Should additional cycles be necessary to correct additional characte~s, the sequence is then repeated for each depression of the error corre~t or erase key on the keyboard 12 or ls continued Imtil the correction key is released after being held in a depressed position.

In cases where the typewTiter 10 i3 capable of printing in a proportional spacing escapement arrangement, additional electronic controls are required to ensure that the character and the underscore are appropr'ately removed.

In the proportional mode~ when the line memory 34 is read to determine the character immediately preceding the print point, the escapement value for that character is determined and the print mechanism is reverse escaped, as described previously, through that escapement value or that number of escapement units corre~ponding to the character read from line memory. Thus it can be said that for narrow characters, a command to erase will result in the underscore type font on the typ~ng element being impacted onto only a short portion of the underscore line with the right end thereof extending onto non-printed paper. This results in the engagement of the correction medium 37 with non-printed paper and has no visual effect of any substance. When a character is read which has a width or escapement value exceeding the width of the underscore, the escapement logic 22 determines that condition from the character and velocity decode logic 18 and inputs a signal to the escapement LE9-77~016 .. .. . . ... . . . . . .. ... .. . .. . . . . ... : . .. .. . ..

7~)~

logic 22 to reverse escape the pr-Lnt carrier 13 a distance e~ual to the width of the underscore. It then commands ~n erase operation as described above wherein the erase media 37 is positlan~d between the type element 15 aad the paper and commands are conveyed from the character and velocity decode log:lc 18 t:o l:he magnet dr-ivers 20 effecting the appropriate positioning oi the type element 15 for the impacting of the underscore type font OlltO the erase media and the erase media then onto che printed page. Upon the completion of the erase cycle the erase underscore logic 42 then commands the escapement logic 22 to reverse escape any remalning value necessary to place the left end of the underscore type font at the left edge of the character.

At this point a second erase cycle, while selecting the underscore through the character and velocity decode logic 18, is accomplished thus removing a second small segment of underscore from the page. Also, this point the type font and print mechanism are properly pasitioned so that the character which has been read from line memory 34 may then l~e selected by way of the character and velocity decode logic 18 to effect the selection of that type font and impacting onto the erase media and thence onto the page for erasure. As each character is read from the memory 3~ the erase underscore logic 42 through the escapement logic 22 controls the escapement register 24 to reflect all intermedlate positions of the pri~t carrier and print polnt through the mutiple cycles. As the print carrier is moved, the photoemitter/sensor 21 signals through the integrator 28 acts to reduce the count in the escapement counter 36 and thus control the magnet drivers 20 which then in turn control the dlrection, drive and escapement magnets. In any cycle when the escapement counter reaches a zero value, the escapement, direction, and drive magnet drivers are turned off and the escapement logic 22 then relea3es the character and velocity decode logic 18 to perform the function of outputting signals to the selection magnet drivers 20.

The controls necessary to control the typewriter 10 which have been explàined above in b~oc~ diagram form are preferably embodied in ., ... . . -- , .

7r~Z

operational sequences of ~he electronlc logic and devlces whlc,h may be represented by the flow charts ln FIC;S. 3 through 7. To more fully understand the operat-f.onal sequenc:es and the lvgic c~ntrols whlch are a part of the block di.agram illustrated in FIG. 1., refer to FIGS, 3 through 7. Referring to FIG. 3, the main flow of the logic contained in the underscore and underscore erase logic are illustrated in conventional flow chart form.

During normal typing operations lk is from tisne to time necessary to cause words or lines of typed material to be underscored. It is alsc necessary, considering the occaslonal error made by a typis~, to have the ability to correct errors made in underscored te~t.

Referring to FIG. 3 and the start point therein, it is assumed that typing is in progress. When a signal is received in the electronic logic it is determined whether the signal which has been received is a character. If the code emanating from the keyboard control unit to the character and velocity decode logic 18 is in fact a character 50, the routine will then branch by the "yes" route to cause the placing of the character into the line memory 52. Upon the completion of the placing of that character 52 into the line memory 34 the routine wil'.
then flow to the print character sub-routine. The prin~ character sub-routine will be e~plained later.

If the character and velocity decode logic 18 does not detect a code representing a character then the logic flow branches through the "no~' path to the question of whether the signal represents a line underscore function 54. In the event that the coded function decode 44 determines that the signal is a line underscore, the line underscore code is then stored into the line memory 56. At the same time that the line underscore code is stored into the line memory 34, a line underscore flag 56 i~ set to indicate upon subsequent commands that the search back through the line memory must be extended until the line underscore flag is encountered.
LE9-77-016' . .

~ 8~

-13~
Upon the completJon of the settlng of the 'Iine underscore f'lag, the routine then branches back to t'he star~ of thls flow path. In the event that the decislon is made that there is no line underscore function 54 received by the coded function decode 4~ the "no" path is followed to the decision bloc~ 60 in wh:Lch the question is asked "is there a word underscore function being received?" If the answer to that question is "yes" then the flow path branches to the underscore routine, to be described more fully below. In the event that the answer to that decision is "no" then the flow passes through the llno branch to the decision block to determine if the functlon being receive~
by the coded function decode block 44 of the electronics as :Lllustrated in FIG. 1, is an erase function 62. If the code does represent an erase function then the flow branches to the erase routlne. If the code is not that of an erase function, then the logic flow branches ':o other routines o the electronics which are not material to this invention.

In the event that the code received by the character and velocity decode logic 18 represents a character and that the logic flow has branched through the storing of ~hat character into line me~ory as indicated in FIG. 3 and described above and that the flow path is subsequently branched to the print character routine, the next functl~n o the electronics is to place a code through the escapement logic ~2 and into the character and velocity decode logic 18 to provide outputs to the magnet drivers 30 as shown 6~ in FIG. ~. These magnet drivers 3~
arè representative of and control the rotation, tilt and veloclty necessary to effect the printing of the selected character. Upon the complet.on of the signals being sent to the magnet drlvers 36, the escapement value is then determined from an escapement table 66 and the value for that character is placed in~o the escapement counter and the escapement register is updated to indicate the destination of the carrier 17 and print element upon the completion of the cycle. Upon the escapemellt counter being loaded with the escapement value representing the char~cter, the escapement direction and drive magnets 30 are then turned on as a .. i .. . ~ .. . . . . . .

t7~2 result of the escapement coun~er 26 being loaded and the carr-Ler ls escaped. As the carrier 17, the photoemitter/sensor 21 together w1th the pitch control will provide feedback signals through the integrator 28 to the escapement counter 36 to reduce the count and at the same t'ime provide a signal to the character and velocity decode logic 18. When the escapement counter 36 ls decremented to ~ero as a result of the photoemitter/sensor pulses indicating movement of the carrier, the escapement counter 36 will turn off the magne~ drivers 30 thus comple,~.ng escapement.

In the event that a word underscore function 60 has been detected by ~he coded functlon decode block ~4 and as a result of the character and velocity decode logic 18 determining that there is no character being keyed at the keyboard, the flow branches to the underscore routine, as described with respect to FIG. 5. Upon the branching to the underscore routine, the value in the escapement register 24, the present carrie~
position, is stored in memory 68 for future use and the preceding characters in line memory is then read 70. Then signals derived fro-,~
the line memory 34 are processed by the underscore logic 46 to determ-ne if the code or character being read from the line memory is a space or tab code 72. If the code is a space or tab code then the underscore logic determines whether the line underscore flag has been set 2~. If the underscore flag has not been set, then the process branches to the playout routine.

If the line underscore flag has been set, then the logic determines 25 whether the code previously detected is a space 76. If the code does represent a space then the stored carrier position is decremented an amount representing the space width 28. If the code represented is not a space, then it must be a tab command and in that case a carrier position, which was stored in line memory at the time the tab comma~ad was initiated, is read into memory as the stored carrier position 80.
Upon completion of the storage of that carrier position code, the routine '7~Z

then branches back to polnt UN 7 to repeat the cycle with respect to the next code immediately precedLng in the llne memory.

After the decision has been made that the code has been in fact a space code and the carrier position has been decremenLed by an amount equa to the syace width, the routine then branches to UM 3 which will be more fully explained subsequently.

If the decision i~ made that the charact:er belng read from the memory i~
not a space or tab code 72, then the logic flow branches to the decision block where the question is raised "is the character a line underscore code?" 82. If the answer to that decision is "yes" then the log-lc checks to detennine whether the line underscore flag is set 8~. If ;he decision with respect to that question is "yes" then the logic then branches to the playout subroutine to be more fully described below.

If the answer to that decision is "no" then the logic will then branch to a path which is the same as if the character was not a line underscore code in decision block 82. At this point, the logic flow has deter~:Lned that the code is not a space, tab, or line underscore code. If that condition exists then the code belng read from the memory must of necessity be an alpha or numeric character. Thus the eighth bit of that character code is turned off or conditioned to a zero state in memory 8 The escapement value is then determined from the table look up and the stored carrier position is decremented that escapement value and rest~red in memory for future manipulation 88. At this point, the underscor, routine is then repeated with respect to each character positione u-~til such time as the routine goes to the playout routlne; which only occurs upon the discovery o~ a space or tab or a line underscore code with the line underscore flag being set appropriately.

Referring now to FIG. 6, which represents the playout routine referred to immediately above, upon the satisfying of the conditions requir~d as described above ~nd illustrated in FIG. 5, the routine will branch to , 7(~

playout routine. As was descr-Lbed earlier wlth respect to FIG. 5, the underscore routine has calculated a pos-ltion as it moves back through the memory which will represent the position to which the carirer must reverse escape before the starting of the actual underscoring of the characters. This position which has been determined as a result of the underscore routine ls referred to as the calculateo carrier position. The playout routine represented by FIG. 6, starts ~y subtracting the immediately above referred to calculated carrier posltion from the position that the carrier actually occupies; that being the present carrier position at the end of the text to be underscored 90 The remainder of this subtraction operation is then placed into the escapement counter 36. The underscore logic 46 then causes the reverse magnet and the escape magnets to be turned on through the escapement counter 36 to effect reverse escapement 9Z. Upon each succeeding loglc lS ~y~le, the escapement counter 36 is then compared with zero 94 and if the value of the escapement counter is not equal to zero then the "no" path is followed and the escapement counter 36 continues to accept control pulses emanating from the photoemitter/sensor 21 decrement 96 the value in the escapement counter 36. At this point, the logic path returnP to the decislon block as the escapement counter equals zero 44. As the e~capement counter 36 i8 decremented it will eventually reach a zero value and the yes path is followed. At this point, the underscore logic will then place a code into the character and velocity decode to effect the printing of the underscore under the character 98. Upon t~e ~S printing of the underscore mark under the character, the velocity and character decode logic 18 will then cause the normal escapement for the underscore character 100. The underscore logic then will compare thP
carrier position upon the completion of the underscore print operation to the posltion which the carrier occupied at the time that the underscore routine was entered 102. This position was stored in memor~
at the beginning of the underscore routine for future comparison. If the carrier is not at the same position, then the underscore logic will then cause the placing of another underscore code under the character and cause velocity decode logic 18 to effect printing and escaping as ~ust previously described.

7l~Z

Upon the carrier reaching the previous positLon, the decision w-lll be made that the carrier is at the previous position and the logic will then cause a branching from the playout routlne ba~k to ~tart in FIG. 3.

In the event that an error has been made in the typing of a character prior to the underscoring or an underscore is placed in a position whicl, the operator does not desire to have underscored, the erase routine ~y be entered as a result of the special functions 26 portion of the keyboard 12 indicating that erasure or correction is to occur. The function decode block 38 as illustrated in FIG. 1 will receive ~he erasure signal and read the next preceding character code in the line memory 34. Upon the function decode block 38 determining that there exists an erase command, the erase logic 42 will assume control and will check the code from line memory 104 to determine if the eigh~h blt of that code is in an oEf condition or a zero state 106. If the eighth bit is not in an off position the routine will branch to other functions not relevant to the erase underscore routine. If the eighth bit is a zero or of~, the "yes" path is followed and the escapement value is then determined for the character code received by the erase logic from memory 108. Upon the determining of the escapement value, it is then compared to the width value 5 to determine if the escapement value is greater than S escapement units 110; which is the width of the underscore mar~.
If the escapement value of the character which has been read from the line~
memory is less than or equal to 5 the "no" path is followed and the carrier is then caused to reverse escape, by substantially repeating the same operation as described earlier by the value of the escapement fcT
character read from memory 112. This reverse escapement is effected by t`ne reverse escapement control of the escapement counter 36 and the reverse and escape magnets drivers 30 as controlled through the escapement logic 22.

Upon the completion of the escapement of the carrier 17 in the reverse direction to the designated position as immediately described above, the erase logic 42 and underscore logic 46 act through the character and .

velocity decode 18 and the escapement loglc 22 to condition thc erase 30 and rotate magnets 20 to effect the posltioning oE an correction medllm 37 between the type element 15 and the prlnted page and ~he appropria~e selection of the underscore character and in then lmpacting of that character onto the erase media 37 to caLLse the removal o~ the underscore from the printed page 114.

Upon the completion of the erasing of the underscore, the erase logic 42 causes the character code read from llne memory 22 to be entered into the character and velocity decode :Logic 18 and controls the escape-ment logic 22 to effect the activation of the erase magnet driver 30together with the selection of the character as controlled by the character and velocity decode logic 18 to cause the character to be erased 116.

If the escapement value of the character read fro~i line memory is greater than 5 escapement units, such as capital IIW'1 and capital "M", then the logic will branch to cause the carrier to reverse escape 5 units and erase 5 units of the underscore (the width of the underscore type font) lg.
Then 5 will be subtracted from the escapement value of the character as determined from the escapement table and the logic will then branch back to the decision block "is the escapement value greater than 5 units?" llO.
At this point the answer will be "no" and the sequence previously described will be followed.

The embodiment which this invention may take may be one of several alternatives forms. One form described above in conjunction with the block diagrams and flow charts illustrates one embodiment. An alterna ive embodiment may be an electronic processor control which may operate in conjunction with a permanently configured read only storage in whicn a series of instructions and codes may be stored. This electronic apparatus would correspond to the apparatus as described in conjunction with FIGS. 1 and 3 through 7.

In such case, an alternative to the 10w d:lagrams lllustrated in FIGS. 3 through 7, codes or com[nands may be stored ln the read only store to cause the electronics to process the informa~ion ~om the keyboard and to control the printer in a predetermined sequence of steps. The commands and codes stored in the read only store may take the form of those attached in Appendix A and Appendix B. Appendix A
is a listing of definitions which indentLfy and are associated ~7ith particular registers or particular bits ~lthin a byte and equates those register designations and or bit designations with mnemonics.

Appendix B is the complete listing of a set of instructions ~hich serve to control the processor and may be programmed or coded as desired in order to control the electronic processor. Particular embodlments of the code or instructions may be modified as desired by one skilled in the art to accomplish the particular function of the invention.
Additlonally it should be recognized that a programmable processor may embody a program which may be written conforming to the requirements of that processor for accomplishing the same result.

Referring to Appendix B, Column 1 is the address, in hexideclmal code, where that particular instruction is stored. Column 2 represents the hexidecimal code for the instruction and is stored in the location designated by the corresponding information in Column 1. Column 3 is the mnemonics indentifying the start point of particular sub-routines.

- Column 4 is the mnemonics for the instruction which the processor thenexecutes. Column 5 contains mnemonics which then, through definitions and equality statements in Appendix A assigns numerical values for registers or bits as appropriate for the -lnstructions contained in Column 4. Column 6 are explanatory comments.

With reference to those bytes illustrated in the two byte columns, these bytes represent how that particular instruction would appear in the read only store memory. The ones and zeros in those bytes are dedicated .... . .. ..

7~

values which remain unchanged for ~hat particular instruction ~7hlle the B contained in the instruction code :Indicates the bits to be tested ~nd the A's are representative cE the address to which the ~n~tructlol series will branch upon the mee~ing of partlcular conditions set fort~, depending upon whether the bits ~ are represented by a 1 or 0.
Referring to other instructions, the letter D represents a fixed valtle in meMory and is determined by the individual implementing the partlc~lar devlce.

The R's are representative o~ the numerical designation for 1 of 32 separate registers which are available for storage of data and which are available to the processor.

Appendix D includes an instruction su = ry which lists the mnemonic, the name of the instruction represented by the mnemonic and a brief description of the function performed by the processor as a result o that particular instruction.

As an aid to understanding the description of the instructions contained in Appendix D, reference should be made to FIG. 8 which is illustrati~e of the flow of the instructions between different registers, memories and accumulators.

While the invention has been particularly shown and described with reference ~o preferred embodiments thereof, it will be understood by those skilled in the art that the ~oregoing and other changes in fo m and details may be made therein without departing from the spirit and scope of the invention.

. . _., 3 70;~

APPENDIX A

MTARG EQUALS O SUBADDRESS OF PAST CARRIER POSITION

LCNT EQUALS 2 ADDRESS OF PRE';ENT CARRIER POSITION

MLCNT EQUALS 4 MEMORY LINE COUNT, ADDRESS LINE I~MORY

PM EQUALS 6 PRINTER MAGNET REGISTER, REPRESENTS OUTPUT
TO PRINTER
REV~fAG EQUALS 1 REVERSE MAGNET

WKl EQIJALS 9 WORKING REGISTER

- CHARACTERS
VELTABL EQUAI,S 200 TABLE THAT CONTAINS VELOCITY VALUE OF
CHARACTERS

VELMAG EQUALS 4 MAGNET T~LAT SELECTS VELOCITY OF IMPACT

Bl EQUALS O FIRST BAIL FROM KEYBOARD

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FIRST BYTE SECOND BYTE

TEST BIT - JU~ EQUAL TJE 1 1 0 B B B A A A A A A A A A A
TEST BIT -JU~ NOT EQUAL TJN 1 1 1 B B B A A A A A A A A A A

BR~YCH BR 0 0 A A A A A A A A A A A A A A

INCREMENT Al 1 0 1 0 1 1 1 0 DECREMENT Sl 1 0 1 0 1 1. 1 1 :

~ .. . . . . . .
__ 3~

3'70~

APPr.NDIX D

Ins~ruction Summary Mnemonic Name Description TJE B,A Test Bit - Jump Equal Test bit B in the accumulato.
and when on, branch to A.
TJN B,A Test Bit - Jump ~nequa]. Test bit B :Ln the accumulato ~nd when off branch to A.
CJE R,A Compare - Jump Equal Compare byte R in B reglster with accumulator and when equal branch to ~.
CJL R,A Compare - Jump Low Compare accumulator to byte R in B register and when accumulator is less than R
branch to A.
BR A Branch Branch to A.
J A Jump Jump to A.
LDL D Load Direct Low Load low half of the accumulator from the instruction. Ze:o high half.
LDH D Load Direct Load the accumulator from the instruction.
LR R Load Register Load accumulator from direct memory. Place direct memorv address in storage address Register.
LBR R Load B Register Load the B Register from direct memory.
LN A Load Ir~direct Loacl the accumulator from indirect memory. (Addre,s given by B Register and 4 ti s of the instruction.) ~ . . . . .

.

7~)Z

~'P~NI)IX D (COllt ~ d) ~Jnemonic Name Description .

STR R Store Register Store the accumulator in direct memory. Place direct memory address .
STN Store Indirect Store the ~ccumulator in indirect memory (Address in Register.) SBS B Set Bit and Store Set bit B in direct memory (address in Storage Address Reglster) to 1.
RBS B Reset Bit and Set blt B in direct memory (address in Store Storage Address Register) to O.
Al Increment Add one to the accumulator.
Sl Decrement Subtract one ~rom the accumulator NOP No Operation Go to next instruction.
ER Emitter Reset Reset Emltter latch.

: ~:

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: :
.

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~ ~ .
~ . .
.~

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A system including a typewriter having means for printing characters on a page in response to keyboard commands, means for printing underscores, memory means for recording codes indicative of said keyboard commands;
escapement means for escaping said means for printing relative to said page, said escapement means responsive to said keyboard commands and said codes for varying the amount of escapement for different ones of said commands and codes, in accordance with predetermined widths of said characters;
means for backspacing;
error correction means responsive to keyboard command for conditioning said typewriter to backspace, for reading said memory in reverse order of said recording, for deleting the read character from said page, and an erase control means, said erase control means comprising:
means for altering said recorded codes to indicate the presence of an underscore;
means for determining the width of said character from said recorded code and for controlling said backspacing means to terminate said backspace movement at a point to align the left end of said underscore with the left edge of said character;
detection means for detecting said altered code;
means responsive to said means for detecting for selecting an underscore character and causing said under-score character to be utilized in the deleting of the underscore mark on said page; and means responsive to the detection of said altered code to initiate a second deletion operation of said error correction means after the operation of said error correc-tion means to delete said underscore.

2. The system of claim 1 wherein said means for determining the width of said character and for controlling said backspace means is further operative to control said backspace means to backspace said print means by an amount equal to the difference of the width of said underscore and said character where said character is wider than said underscore, in combination with a backspace movement equal in width to said underscore and said corrections operative to cause said deletions operation after each of said back-spacing movements.

3. The system of claim 1 or 2 wherein said error correction means controls said escapement means to backspace said print means less than the width of said character when said character width is greater than said underscore width, and to cause repetition of said deletion operation after each backspace movement.