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BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention disclosed herein related to data processing devices and more
particularly relates to post processing devices for the detection of
typographical errors resulting from the use of keyboards and the like.
2. Description of the Prior Art
One of the more burdensome problems to principals in the word processing
industry is the necessity for retyping of documents due to spelling
typographical errors. The invention of typewriters with electronic and/or
magnetic memories has aided in the solution to this problem by permitting
the typist to only retype the error words while the remainder of the text
is played out automatically at high speed. However, the likelihood of
spelling error free output from these devices is only as good as the
spelling ability of the typist and the likelihood that error words will be
overlooked is high.
A significant advance in the art of misspelling detection has been
contributed by W. S. Rosenbaum in U.S. Pat. No. 3,995,254, issued Nov. 30,
1976, entitled "Digital Reference Matrix to Word Verification", and
assigned to the same assignee as the present application. A digital
reference matrix is disclosed therein which provides for compact storage
of a dictionary of correctly spelled words to be used to verify input
words from a keyboard, character recognition machine or voice analyzer. A
vector representation for each word in the dictionary is calculated in the
form of a magnitude and unique angle combination. These representations
are stored in a memory. Input words to be checked for spelling errors then
undergo a magnitude and angle calculation, the results of which are
compared to the dictionary/memory. An output signal is generated
indicating the result of the compare. While Rosenbaum provides an accurate
means for verifying the spelling of input words, it does not provide for
efficient operation in word processing systems where throughput is the
paramount requirement. This lack of efficiency is due to the disruption of
the operator's typing rhythm caused by signalling each time a typed word
does not appear in the dictionary.
SUMMARY OF THE INVENTION
The invention provides a dictionary and an error list memory in a word
processing system which includes processing logic, a keyboard, a printer
and a page of storage. The error list memory has associated with it,
pointers to load and unload the memory, a counter to describe which word
in the list is being corrected, a location list which contains in sequence
the absolute horizontal and vertical position in text of the end of each
word on the page found in the error list, and a pointer to indicate the
point being accessed in this location list.
Each word keyed on the keyboard is compared to the contents of the
dictionary. Any word that is not found in the dictionary is stored in the
error word memory along with its horizontal and vertical position on the
page. Prior to storing a word in the error memory, the memory is searched
to determine if the same error has previously occurred. If it has, a
pointer is set at the previous occurrence indicating the address of the
next occurrence of the error.
After a page is completed the error list memory is addressed for error
words. The carrier automatically repositions itself at the first
occurrence of the first error word in the error list memory. If the word
is spelled correctly, the operator depresses a word correct key and a
correct bit is set in each subsequent occurrence of the word in the error
list memory. The system uses the correct bit to ignore the word when it is
again encountered.
If the word is incorrectly spelled, the operator depresses a word incorrect
key which causes automatic erasure of the word from the page. The correct
word is then keyed in by the operator and the system automatically
corrects all subsequent occurrences of the word in the memory and sets a
word incorrect bit. A word subsequently encountered with its incorrect bit
set is automatically erased from the page and correctly typed without
operator intervention.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a block diagram of a word processing system including the
apparatus of the present invention.
FIG. 1A is a perspective view of a typewriter including a keyboard and
printer.
FIG. 2 is a diagramatic illustration of the typewriter shown in FIG. 1
together with the control circuitry by which the typewriter is controlled.
FIG. 3 is a diagramatic illustration of the circuitry for the dictionary
verification function.
FIG. 4 is a diagramatic illustration of the error word memory and its
associated control circuitry.
FIG. 5 is a system timing chart for controlling system operation during
keying of text on the keyboard.
FIG. 6 is a system timing chart showing the operation of the system at the
end of a page of text.
FIG. 6A is a continuation of the system timing chart of FIG. 6.
DETAILED DESCRIPTION
Referring now to FIG. 1, there is shown in block diagram form a word
processing system. The system includes processing logic 1, display 2, auto
erase 25, printer 22, keyboard 30, word queue 307, dictionary 300, page
memory 304, and error memory 325. The printer may be a serial
character-by-character impact page printer or typewriter 10 (FIG. 1A) that
can be generally like the well known IBM SELECTRIC I/O Writer as described
in IBM Customer Engineering SELECTRIC I/O Writer Instruction Manual,
form/part number 241-5159-1, revised Nov. 12, 1962, published by
International Business Machines Corporation, Armonk, New York. The
typewriter 10 includes the well known printing mechanism 11 comprising a
type element having characters shaped type thereon. The type element
together with a page supporting impact resistant platen 13 defines a print
point 20. The typewriter 10 also includes a keyboard 30 having printing
control keys and print position moving keys such as a space bar 32, line
return key, backspace, and line feed key.
Referring now to FIG. 2, the typewriter 10 is provided with horizontal and
vertical motion transducers 54 and 43 respectively, each of which can be
similar in theory and operation to that disclosed in U.S. Pat. No.
3,579,195. The horizontal motion transducer 54 comprises a pulse emitting
wheel 55 which generates strobed position and direction information in
photosensing mechanism 56 by which displacement of the lead screw 17 in
individual character increments is measured. Suitable control circuitry
including a counting register provides a digital horizontal print point
position sensing device 57. The sensing device 57 stores a seven digit
true binary code output that numerically represents the column position of
print point 20 along the writing line 22.
The vertical motion transducer 43 is substantially identical to transducer
54 and includes an emitter wheel 44 and optical sense mechanism 45.
Suitable control circuitry including a counting register provides a
digital vertical print position sensing device 46. Sensing device 46
stores only a six digit binary code output which is numerically
representative of the writing line position of the page 21 within the
typewriter 10.
The lead screw 17 is driven through gears 18 and 19 by a direct current,
forward and reverse drive motor 50. The carrier 16 thus is positioned
along the length of platen 13 by operation of the motor 50. To obtain
precise positioning of the print point 20, a detent member 51 is normally
engaged with a ratchet wheel 52 on the lead screw 17. When seeking a new
typing field, electro-magnet 53 is activated to withdraw the detent member
51 from ratchet wheel 52 and thereby free the lead screw 17 for movement
prior to driving of lead screw 17 by motor 50. Termination of lead screw
rotation is followed by release of electro-magnet 53 and re-entry of the
detent member 51 to again precisely position and hold the lead screw 17.
In summary it is seen that the typewriter 10 provides a mechanism capable
of positioning the print point 20 horizontally and vertically both in the
forward and reverse directions. While a type impact printer has been
illustrated, those of skill in the art will recognize that a serial
printer operating to produce visibly hard copy by other techniques would
be equally appropriate. For example, the printing mechanism could employ a
controlled ink jet spray, a thermal matrix, or an optical character
generator with equal facility. Also, the printer could be replaced by
other suitable types of output devices such as video displays or audio
output device.
In operation, a page 21 is inserted by the operator to align a fixed
position on the page 21 with the print point 20. Reset key 61 is depressed
to set the horizontal position sensing device 57 and vertical position
sensing device 46 to a zero or normalized position. Thereafter, all
displacement of the print point 20 relative to the page 21 is accounted
for and the horizontal and vertical print point position sensing devices
57 and 46 as unit displacement is added or subtracted with the motion of
either the platen or carrier 16.
Referring now to FIG. 3, keyboard 30 is connected by data bus 501 to word
queue 307 and page memory and print control 304. The page memory and print
control apparatus is fully disclosed in U.S. Pat. No. 3,780,846, issued
Dec. 25, 1973, to R. A. Kolpek, et al., assigned to the same assignee as
the present invention and expressly incorporated herein by reference.
Characters keyed on the keyboard are stored in the page memory and the
print control controls the print mechanism in printer 22 along bus 502 to
print each character on the print media 21.
Word queue 307 stores each character as it is keyed on keyboard 30. The
output of word queue 307 is connected to assembly algorithm 303 through
data lines 503. Assembly algorithm 303 calculates a vector representation
for the group of characters stored in word queue 307 in accordance with
the theory and apparatus disclosed in U.S. Pat. No. 3,995,254, entitled
"Digital Reference Matrix for Word Verification", issued Nov. 30, 1976, to
W. S. Rosenbaum, assigned to the same assignee as the present invention,
and expressly incorporated herein by reference. The assembly algorithm 303
is connected to sequence control circuit 306 through line 523 and is
activated to calculate the vector representation for a word stored in word
queue 307 when a space, tab, or carrier return is keyed on keyboard 30 and
sensed by sequence control circuit 306 over line 504. The sequence control
306 and the gates and registers on FIGS. 3 and 4 make up the processing
logic on FIG. 1. The sequence control 306 provides the sequential timing
signals shown in FIGS. 5, 6, and 6A for initiating the operations in the
components of the processing logic 1 of FIGS. 3 and 4. The detailed
discussion of the timing signals appears in the operation section of the
specification. Circuits that may be used as a sequence control for a
sequentially operating system are well known in the prior art. For
example, a read only memory may be used where each of the signals input to
the read only memory accesses a specified address within the memory which
outputs one signal or a series of signals in response to the input. Basic
sequence control circuits exist in text books. As an example, the text
book entitled " Arithmetic Operations In Digital Computers" by R. K.
Richards, copyright 1955, published by D. Van Nostrand Company, Inc. at
pages 337-342 features two exemplary circuits. The first of these circuits
is a clocked or "synchronous" control circuit and the second one is an
unclocked or "asynchronous" control circuit.
Richards' asynchronous control circuit comprises an operation matrix having
an output line for each of the operations the system will perform and
having miscellaneous input lines from other devices in the system. The
operation matrix and the miscellaneous input lines communicate with a
series of AND gates and delays. Inputs to the AND gates pass through the
delays to provide output command signals which are used to run the system
in the manner shown in FIGS. 5, 6 and 6A of this application. In an
asynchronous control system, as in the sequence control circuit of this
invention, "there is no fixed time reference for the execution of the
operations. Instead, one operation is commenced as soon as the previous
one is completed. To accomplish this purpose, the circuits must be
arranged so that, at the completion of each operation, a signal is
generated which may be used to initiate the next one". The output of
assembly algorithm 303 is connected to magnitude register 301 and angle
register 302 over lines 505. Dictionary memory 300 contains vector
representations for a predefined dictionary of words. When a word end
signal is sensed by the sequence control circuit 306, it outputs a read
signal to dictionary memory 300 over line 506. The address for the read is
defined by the magnitude and angle calculated for the word in word queue
307 by assembly algorithm 303. If the word is correctly spelled, the
output of the dictionary memory 300 will be on output line 508 to sequence
control circuit 306 so indicating. The sequence control circuit 306 then
resets word queue 307 over line 521 and the dictionary is ready to verify
the next word.
A second output from dictionary memory 300 is connected to assembly
register 305 over line 507. If the word in word queue 307 is not found in
dictionary 300, then a signal so indicating is output on line 507 to set
assembly register 305. The output of assembly register 305 is connected to
sequence control circuit 306 over line 522.
Referring now to FIG. 4, sequence control circuit 306 has an output to
error list memory address register 323 over line 510. An input to the
sequence control circuit 306 over line 522 from assembly register 305
causes the sequence control circuit to reset memory address register 323
to the first location in memory 325 over line 510. A read signal output
from sequence control circuit 306 is connected to error memory control
over line 511. A signal on line 511 causes memory control to read from the
memory, at the address specified by memory address register 323, the error
word into error word input/output register 310, the page position into
page position I/O register 314 and the next cell location into the next
cell location I/O register 322. Error word input/output register 310
serves three functions. When an error word occurs during input keying,
each word already stored in error list memory 325 is read out into error
word input/output register 310 for comparison by comparator 311 to the
word stored in word queue 307. The purpose of this comparison is to
determine if the error word stored in word queue 307 has previously been
stored in the error list memory 325. The second function of the error word
input/output register 310 is to receive a word from word queue 307 through
gate 308 that is to be written into the error list memory 325. The third
function of the error word input/output register 310 is utilized during
the error correct operation wherein each word in the error list memory 325
is gated from the error word input/output register into the word queue 307
through gate 309 for transfer over line 501 to the page memory and print
control 304 for correction.
The page position I/O register 314 has an input connected to gate 313 which
is connected to the vertical position sense register 46 and the horizontal
position sense register 57 over lines 47 and 58 respectively. The page
position input/output register temporarily stores the vertical and
horizontal locations of a word on the print media 21. During the input
keying phase of operation, the page position I/O register 314 stores the
location of an error word which is to be written into error list memory
325. During the error correct phase of operation, page position I/O
register 314 passes the location of a word to be corrected through gate
312 over lines 82 and 92 to registers 83 and 93 to cause the carrier to
space to the defined print position on the media 21.
The next cell location register 322 controls the contents of the next cell
in error list memory 325 which is associated with each error word stored
in the error list memory. The next cell defines whether or not an error
word appears more than one time in the error list memory 325. If the word
appears more than one time then the next cell location associated with
that word will contain the address of the next occurrence of the word in
the error list memory 325. During the input phase of operation, the next
cell location is read out with each error word during the comparison to
the contents of the word queue 307. If a word already stored in the error
list memory 325 is equal to the word in the word queue 307 and the next
cell location associated with that the word is empty, then the address at
which the word in word queue 307 will be stored is written into the next
cell location of the word already stored in error list memory 325. During
playout, the next cell location is used to automatically correct the error
in all subsequent locations in the error list memory once the word is
corrected at its first occurrence.
The new cell register 317 always contains the address of the next empty
cell in the error list memory. During the input phase when a word is to be
written into the error list memory the contents of the new cell register
are gated through gate 318 into the next cell location register 322 so
that an empty cell location is recorded with the word. The word correct
register 316 is connected to sequence control circuit 306 over line 556
into error list memory 325. During the error correct phase of operation
when a word appears in the error list memory because it was not found in
the dictionary memory 300, but which is actually spelled correctly, the
operator will activate a key on keyboard 30 to set the word correct
register 316. The word correct register 316 then causes a correct bit to
be set in each occurrence of the word in error list memory 325.
Thereafter, when the word is encountered in the error list memory 325 and
has its correct bit set, it is simply ignored. The word incorrect register
315 is connected to sequence control circuit 306 through line 562 and to
error list memory 325. During the error correct phase when a word appears
in the word queue that is incorrectly spelled then the operator will
activate an incorrect key on the keyboard 30. The incorrect key sets word
incorrect register 315 and activates an incorrect bit at each occurrence
of the word in error list memory 325. Each additional occurrence of the
word is also automatically corrected at this time. Thereafter, during
playout whenever the word appears it is automatically erased from the
print media 21 and the corrected version inserted in its place.
While in the preferred embodiment of the invention the input device is a
keyboard, it is well understood that it is within the skill of the art to
substitute other input devices without changing the spirit or scope of
this invention.
OPERATION
FIG. 5 shows a timing chart representing the input phase of operation of
the system. Referring to FIGS. 3 and 4 in conjunction with FIG. 5, input
characters keyed on the keyboard 30 are passed to word queue 307 and page
memory and print control 304 over data bus 501. The print control section
of block 304 passes the characters onto printer 22 over data bus 502. As
each character enters the word queue 307 it is passed over line 503 into
the assembly algorithm 303. At the end of a word, a space, tab, or carrier
return pulse passes from keyboard 30 over line 504 to the sequence control
circuit 306. Receipt of a space, tab or carrier return causes the sequence
control circuit 306 to send a signal on line 506 to read from the
dictionary memory the word defined by the contents of the magnitude and
angle registers 301 and 302 generated by the assembly algorithm 303. If
the word is not found, which would indicate that it is incorrectly
spelled, then the assembly register 305 is set over line 507. This brings
up a signal on line 522 from the output of assembly register 305 to the
input of sequence control circuit 306. The input signal to sequence
control circuit 306 on line 522 causes the sequence control circuit 306 to
output a pulse on line 510 to reset memory address register 323 to the
first memory location in error list memory 325. Sequence control circuit
306 then causes a read signal on line 511 to read the first word in the
error list memory 325 into the error word input/output register 310 along
with its corresponding page position into the page position I/O register
314 and its next cell location into next cell location register 322. The
word just read from the error list memory 325 into error word input/output
register 310 is compared to the present incorrect word stored in word
queue 307 by comparator 311. The memory address register 323 is then
incremented to the next memory location over line 512. This comparison
sequence is repeated for each word already stored in the error list memory
325.
If the word in word queue 307 compares equal to any word already stored in
error list memory 325, an output signal will be generated from the
comparator 311 to the sequence control circuit 306 on line 513. In FIG. 5
an equal comparison appears after the second read pulse on line 511 which
brings up the pulse on line 513 indicating that the word is found in the
error list. When a word is found to already appear in the error list
memory 325, the contents of the next cell location register 322
corresponding to that word is tested on line 514 by the sequence control
circuit 306. If the contents of the next cell location indicates that it
is full this means that the word appears subsequently in the error list
memory also. Reading from the error list memory into the error word
register 310, page position register 314 and next cell location register
322 continues until the word is subsequently found and its next cell
location is empty as shown by no pulse on line 514. At this time, the
sequence control circuit 306 outputs a gate signal on line 516 to gate 318
the contents of the new cell register 317 into the next cell location I/O
register 322. This places the address of the next empty cell in the next
cell location I/O register 322. A write signal is then produced by
sequence control circuit 306 on line 515 to the memory control section of
the error list memory 325. This write signal causes the contents of the
error word input/output register 310, the page position I/O register 314,
and the new contents of next cell location I/O register 322 to be
rewritten into the error list memory 325.
The next read signal on 511 from sequence control circuit 306 to the error
list memory 325 will produce an empty cell signal on line 517 from error
word input/output register to sequence control circuit 306. At this point
the memory address register 323 is reset by a signal on line 510 and the
contents of vertical position register 46 and horizontal position register
57 are gated by a signal on line 518 through gate 313 into the page
position I/O register 314. Also, the contents of the word queue 307 are
gated through gate 308 by a signal on line 519 into the error word
input/output register 310. The sequence control circuit 306 then outputs a
write signal on line 515 to the memory control section of the error list
memory 325 to write the contents of the error word input/output register
310, page position I/O register 314, and next cell location I/O register
322 into the error list memory 325. The new cell register 317 is then
bumped over line 520 to the address of the next empty cell in the error
list memory. Following this, a final read from the error list memory 325
indicates that the next cell location is empty and the word queue 307 is
reset and an assembly finished signal is output by the sequence control
circuit to the assembly register 305 on line 509. The preceding sequence
is repeated for each word that is keyed on the keyboard and does not
appear in dictionary until the operator enters a end of page signal on key
61.
Keying of an end of page signal on keyboard 30 initiates a verify signal on
line 550 to the sequence control circuit 306. Since the memory address
register 323 is reset upon the completion of each operation during the
input sequence, it already contains the address of the first location in
the error list memory 325. Sequence control circuit 306 initiates a read
signal on line 511 to the memory control section of error list memory 325.
This read causes the contents of the first cell in the error list memory
325 to be transferred into the error word input/output register 310, the
page position I/O register 314, and the next cell location I/O register
322. The sequence control circuit 306 signals gate 312 on line 552 to gate
the contents of the page position I/O register on data busses 82 and 92
into binary registers 83 and 93 of FIG. 2. As is well known in the art,
these registers 83 and 93 are constructed to be overridden by whatever
information is gated into them. The contents of registers 83 and 93 are
compared by comparators 85 and 95 to the contents of horizontal position
sense register 57 and vertical position sense register 46 which contain
the present print position of the carrier mechanism on the print media 21.
A start carrier and page positioning signal is initiated by the sequence
control circuit on line 553. The signal on line 553 sets a start latch 101
to activate an output line 102. The start signal is then applied to the
horizontal detent control AND circuit 104 and into enabling gates 84 and
94 respectively of horizontal compare circuit 85 and vertical compare
circuit 95.
If horizontal repositioning is required, that is, if the comparison is
unequal, indicating that the carrier is not at the location of the
misspelled word on the print media, a "not horizontal stop" signal will be
presented by line 86 to the inverted input to AND circuit 104 and the
coincidence will be satisfied. Electromagnet 53 is thus activated to
withdraw detent 51 from ratchet 52. Horizontal compare circuit 85 will
provide one of three outputs respectively on a forward drive output line
87, a reverse drive output line 88 and the stop drive output line 86.
Compare circuit 85 functions to determine whether the binary code
presented by horizontal print point position sensing device 57 on lines 58
is greater, less than or equal to the binary code presented by register 83
on lines 89.
If the binary code on lines 89 is greater than that on lines 58, a signal
will be presented to the forward drive output line 87 which is connected
to the motor 50 so as to drive the motor 50 in a direction to move carrier
16 to the right by rotation of lead screw 17. The rotation of lead screw
17 is sensed by optical sensor 56 in terms of the number of pulses in a
direction of lead screw rotation as described in U.S. Pat. No. 3,579,195.
These pulses are added to the original binary number retained in the
horizontal print point position sensing device 57 to continuously update
the binary code presented by lines 58 to compare circuit 85. When the
binary code presented on lines 58 equals the binary code presented on
lines 89, the signal on forward drive line 87 will be removed and in its
place a signal will be generated on stop line 86. This signal provides an
input to stop AND circuit 105 and also applies a horizontal stop signal to
horizontal detent AND circuit 104 thereby completing the required
coincidence necessary to deactivate electromagnet 53 and permit detent
pawl 51 to reengage lead screw detent ratchet 52 to securely retain the
newly obtained horizontal position of carrier 16.
The same operation occurs if the binary code presented on lines 89 is of a
lesser magnitude than that presented on lines 58 with the exception that
the compare circuit output signal would appear on reverse feed line 88 to
drive the motor 50 in a direction such that carrier 16 is displaced
leftwardly by rotation of the lead screw 17. This displacement of the lead
screw 17 decrements the horizontal print point position sensing device 57
to reduce the binary code applied to lines 58 until it becomes equal to
that applied by lines 89. Vertical compare circuit 95 operates like
horizontal compare circuit 85 and determines the difference between a
desired vertical position as presented in the form of a binary code by
register 93 on lines 96 with the current print position as presented in
binary form on lines 47 from the vertical print point position sensing
device 46. If the binary code presented on lines 96 is greater than that
presented to the compare circuit 95 by lines 47, the line feed signal will
be applied to output line 97 to energize line feed magnet 41 and cause
repeated stepping of the platen to move the print point 20 toward the
bottom of the page 21. Motion of the platen is sensed both in magnitude
and direction by optical sensor 45 which increments the vertical print
point position sensing device 46 to continuously update the binary code
applied to line 47. When the code applied to line 47 equals that presented
on line 96, the output signal on feed line 97 is removed and an output
signal is applied to vertical feed stop line 98 which is connected to the
stop AND circuit 105. A signal applied simultaneously by line 98 and line
86 to stop AND circuit 105 generates an output on line 106 to reset start
latch 101 and terminate the operation. At this time the print element 11
is positioned at the last character in the word which is to be corrected
and a signal on line 554 indicates completion of positioning to the
sequence control circuit 306.
As soon as the word at the address specified by the memory address register
323 has been read from the error list memory into the error word
input/output register 310, page position input/output register 314, and
next cell location input/output register 322, the sequence control circuit
306 senses line 514 which is "high" indicating that the next cell location
I/O register is full and correspondingly that the word under consideration
appears more than once in the error list memory 325. Sequence control
circuit 306 then activates gate 319 over line 557 to pass the address in
memory address register into new cell register 317 thereby storing the
address of the first occurrence of the word in error list memory 325.
Sequence control circuit 306 activates gate 321 over line 558 to pass the
address in the next cell location register 322, which indicates the
address of the next occurrence of the word, into the memory address
register 323.
After the print element has been positioned to the last character of the
word, the operator observes the word to determine if the word is spelled
correctly or incorrectly. In the example under consideration, the first
word observed is spelled correctly and therefore the operator presses the
word correct key on the keyboard 30 which causes a pulse on line 555 to
the sequence control circuit 306. The sequence control circuit activates
word correct register 316 over line 556. A second read from error list
memory 325 is then executed by sequence control circuit 306 over line 511.
This read reads the second occurrence of the error word from the error
list memory into the error word input/output register 310, page position
I/O register 314, and next cell location I/O register 322. Having the word
correct register 316 set during a read operation inhibits the signal on
line 552 from causing a repositioning of the carrier. Following this read,
the signal on line 514 indicates that the next cell location register 322
is "low" and that this is the last occurrence of this word in the error
list memory 325. Sequence control circuit 306 then initiates a write
signal on line 515 to the memory control section of error list memory 325
causing the word stored in error word register 310, page I/O position
register 314, and next cell location register 322 along with the word
correct bit to be rewritten back into the error list memory 325. Having
the word written in the error list memory 325 with the correct bit on will
cause the word to be ignored when it is subsequently addressed. This step
is repeated for each occurrence of the same word in the error list memory
325. Following the write into the error list memory 325, sequence control
circuit 306 resets the word correct register 316 over line 559 causing
line 556 to become "low". Gate 320 is then activated by the sequence
control circuit over line 560 to gate the contents of the new cell
register 317 into the memory address register 323. This places the initial
location address back into the memory address register. The memory address
register 323 is then bumped over line 512 by sequence control circuit 306
to the address of the next word in the error list memory 325. A read is
then initiated by the sequence control circuit to the memory control
section of the error list memory 325 over line 511. At the completion of
the read cycle, the output of the word correct register on line 556
becomes "high" indicating that the word just read is one that was found to
be correct during the previous cycle. Therefore, no positioning takes
place and the sequence control circuit 306 initiates a write on line 515
to the memory control section of error list memory 325 to rewrite the word
into the memory. A signal is then initiated on line 559 to reset the word
correct register 316. The memory address register is then bumped over line
512 to the address of the next error word in error list memory 325 and a
read is initiated on line 511 to read the word and its corresponding
position information into the error word register 310, page position
register 314, and next cell location register 322.
Following the read operation, gate 312 is activated by a signal on line 552
to gate the contents of the page position I/O register 314 into binary
registers 83 and 93 to start repositioning the carrier to the position of
the last character in the word on media 21 over line 553 as previously
described. Line 514 becomes "high" indicating that the next cell location
register 322 is full. The contents of the memory address register are then
gated through gate 319 by a signal on line 557 into new cell register 317
and the contents of the next cell location register 322 are gated through
gate 21 into the memory address register 323 by a signal on line 558.
Sequence control circuit 306 also activates gate 309 over line 564 to pass
the contents of the error word register 310 into word queue 307.
Following repositioning of the carrier to the last character in the word
under consideration, the operator must again make a choice as to whether
the word is spelled correctly or incorrectly. In the example under
consideration, a signal is produced on line 561 from the keyboard to the
sequence control circuit indicating that the word is spelled incorrectly.
This causes the sequence control circuit 306 to set the word incorrect
register 315 over line 562. The signal on line 561 also activates page
memory and print control 304 to initiate over line 563 erasure of the
characters on the page by the printer 22. The printer is equipped with an
erase ribbon 27 and other additional erase apparatus as is fully disclosed
in U.S. Pat. No. 3,780,846, which is expressly incorporated herein by
reference. If the word to be entered has more or less characters than the
error word on the page, the operator may control the apparatus of U.S.
Pat. No. 3,780,846 to erase the entire line or any portion thereof as is
necessary.
Upon completion of the erasure, a signal is produced on line 566 from page
memory and print control 304 to sequence control circuit 306. The operator
then enters the correct characters on keyboard 30 which are transferred on
line 501 to page memory and print control 304 and into word queue 307.
Page memory and print control 304 causes the characters to be printed upon
printer 22 over line 502. Upon completion of keying of the corrected word,
the operator enters a space by depressing the space bar 32 which signals
the sequence control circuit 306 over line 504. The sequence control
circuit 306 then initiates a read on line 511 to read the next word from
the error list memory 325. Since the next cell location register 322 was
full on the previous read cycle and that address was gated into the memory
address register this read occurs at the address of the next occurrence of
the same error word in the error list memory. Again, the next cell
location address register 322 presents a "high" signal on line 514
indicating that the same word occurs at a succeeding location in the error
list memory 325. Since the word in the error word input/output register
310 is the same as the word just corrected, the sequence control circuit
306 initiates a write signal on line 515 to write the contents of the word
queue 307 into the error list memory 325. Since at this time the word
incorrect register 315 is presenting a "high" signal on line 562 an
incorrect bit is also written into the error list memory 325 with the
word.
Following the write into the error list memory 325, sequence control
circuit 306 activates gate 319 over line 557 to gate the contents of
memory address register 323 into the new cell register 317. The memory
address register 323 then has the contents of the next cell location
register 322 gated into it through gate 321 by a signal on line 558 from
sequence control circuit 306 so that now the memory address register
contains the address of the next occurrence of the same word in the error
list memory 325. The sequence control circuit 306 then initiates a read
signal on line 511 from error list memory 325. Following this read the
output of the next cell location register 322 on line 514 is low
indicating that this is the last occurrence of this word in the error list
memory 325. The correct word from the word queue 307 is once again written
into the error list memory 325 in response to a write signal on line 515
from sequence control circuit 306.
Since the same word does not occur in the error list memory 325 again as
indicated by the output on line 514 from the next cell location register
322, the sequence control circuit ini | | |
