Ediate arithmetic results extra bit for floating decimal control and correction of false interm

Claim 2

A calculator of the digital type including in combination: a pair of data registers, each having a plurality of orders for storing digital data, each order having n+1 bits, n of said bits as a group expressing a digit and including a least significant bit and a most significant bit, means for storing a radix point in each register as a predetermined binary value in the remaining bit of the order in which there is stored the digit associated with said radix point, operation initiating means. means for radix point alignment of the data in said pair of registers in response to said initiating means, means for performing arithmetic operations on the data in said pair of registers in response to said initiating means and subsequent to said alignment, said operations involving interdigit carries or borrows and the results of said operations being stored in a particular one of said pair of registers in the form of false n-bit groups for each result digit, and said arithmetic operations means comprise means for performing said interdigit carries or borrows through the remaining bit of each order, said carry or borrow being effective between the most significant bit of the digit in a given order and the least significant bit of the digit in the next higher order, and for recording said carry or borrow as a binary value in said remaining bit of said given order, means for correction if each false n-bit group after a said arithmertic operation, according to the value in the remaining bit of each order in said particular register, and means responsive to the remaining bits in each order of the other of said pair of registers for recording identical values in the remaining bits of said particular register after correction of said false n-bit groups.

Claim 3

A calculator as defined in claim 1 wherein said remaining bit is the most significant in a sequence of (n+1) bits.

Claim 4

A calculator as defined in claim 2, wherein said calculator is of the binary-coded decimal type, each order of said registers comprising five binary bits, four bits of which are used to express a decimal digit; said radix point being a decimal point stored as a ''''1'''' in the fifth bit of said order storing the associated digit; and said binary value for an interdigit carry or borrow being recorded over said stored decimal point in response to occurrence of said carry or borrow in the order where said decimal point is stored.

Claim 5

A calculator as defined in claim 3, wherein the binary-coded digits are stored in excess-three code, and said correction means comprise means enabled during an addition; And operable to add a three to a false bit group if there was an interdigit carry and for subtracting a three if there was not.

Claim 6

A calculator as defined in claim 3, wherein the binary-coded digits are stored in excess-three code, and said correction means comprise means enabled during subtraction and operable to subtract a three from a false bit group if there was an intergidit borrow and for adding a three if there was not.

Claim 7

A calculator as defined in claim 3, wherein said means for performing said interdigit carries or borrows further include means enabled during an addition and storing a particular one of the binary values in said fifth bit of a respective order if there was a carry from that order, and the other of said binary values if there was not; and means enabled during subtraction and storing the other of said binary values in said fifth bit of a respective order if there was a borrow propagated from that order, and the particular one of the binary values if there was not.

Claim 8

A calculator as defined in claim 3, wherein said means for performing said interdigit carries or borrows further include means enabled during an addition and storing a ''''1'''' in said fifth bit of a respective order if there was a carry in that order, and a ''''0'''' if there was not; and means enabled during subtraction and storing a ''''0'''' progated from said fifth bit of a respective order if there was a borrow in that order, and a 1'''' if there was not.

Claim 9

A calculator as defined in claim 3, wherein said operation initiating means include a set of manually depressible function keys and said radix point storing means include a manually depressible decimal point key, and further including means for automatically entering a decimal point at the order storing the rightmost digit of an entered number upon depression of a function key of said set, and means disabling said automatic decimal point entry means upon depression of said decimal point key prior to depression of a function key of said set.

Claim 10

A calculator of the binary-coded digital type including in combination: a set of registers for storing coded digits in a plurality of orders, each order having five binary bits, four of said bits being used to express a coded digit, means for entering coded digits in one of said registers, means for entering a radix point in said one register following entry of any one said digit of a number, said radix point being entered as a ''''1'''' in the remaining bit of the order wherein said one digit is stored, means for performing arithmetic operations on digits of said one register, said operations involving intergit carri or borrows and the result digits obtained from said operation being stored in an other of said registers in the form of f four-bit codes, and said arithmetic operations means comprise means for performing said interdigit carries or borrows through the remaining bit of each order, said carry or borrow being effective between the most significant bit of the digit code in any given order and the least significant bit of the digit code in the next higher order, and a binary value being recorded in said remaining bit of the given order as an indication of each carry or borrow, means for correction of each false code after a said arithmetic operation, according to the binary value in the remaining bit of each order in said other register, and means responsive to the radix point information in the remaining bits in the orders of said one register for storing a radix point relative to said result digit codes in said other register subsequent to correction of the false codes.

Claim 11

A calculator of the binary-coded digital type including in combination: a set of registers for storing coded digits in a plurality of orders, each order having five binary bits, four of said bits being used to express a coded digit, means for entering coded digits in one of said registers, means for entering a radix point in said one register following entry of any one said digit of a number, said radix point being entered as a ''''1'''' in the remaining bit of the order wherein said one digit is stored, means for performing arithmetic operations on digits of said one register, said operations involving intergit carri or borrows and the result digits obtained from said operation being stored in an other of said registers in the form of f four-bit codes, and said arithmetic operations means comprise means for performing said interdigit carries or borrows through the remaining bit of each order, said carry or borrow being effective between the most significant bit of the digit code in any given order and the least significant bit of the digit code in the next higher order, and a binary value being recorded in said remaining bit of the given order as an indication of each carry or borrow, means for correction of each false code after a said arithmetic operation, according to the binary value in the remaining bit of each order in said other register, and means responsive to the radix point information in the remaining bits in the orders of said one register for storing a radix point relative to said result digit codes in said other register subsequent to correction of the false codes.

Claim 12

A calculator as defined in claim 9, wherein each binary code identifies a decimal digit, said remaining bit is the fifth bit of each order, and the radix point is a decimal point stored as a 1'''' in the fifth bit of the order storing said one digit, and further including means effective subsequent to sAid correction and said storing of a radix point relative to said result digit codes, and responsive to the data in said other register for displaying the result digits with said decimal point properly located.

Claim 13

A calculator as defined in claim 9, wherein the binary-coded digits are stored in excess-three code, and said correction means comprise means enabled during an addition and operable to add a three to a said false code if there was an interdigit carry and for subtracting a three if there was not.

Claim 14

A calculator as defined in claim 9, wherein the binary-coded digits are stored in excess-three code, and said correction means comprise means enabled during a subtraction and operable to subtract a three from a said false code if there was an interdigit borrow and for adding a three if there was not.

Claim 15

A calculator as defined in claim 9, wherein said means for performing said interdigit carries or borrows further include means enabled during an addition and storing a particular one of the binary values in said fifth bit of a respective order if there was a carry from that order, and the other of said binary values if there was not; and means enabled during subtraction and storing the other of the binary values in said fifth bit of a respective order if there was a borrow propagated from that order, and said particular one of the binary values if there was not.

Claim 16

A calculator as defined in claim 9, wherein said means for performing said interdigit carries or borrows further include means enabled during an addition and storing a ''''1'''' in said fifth bit of a respective order if there was a carry from that order, and a ''''0'''' if there was not; and means enabled during subtraction and storing a ''''0'''' in said fifth bit of a respective order if there was a borrow propagated from that order, and a ''''1'''' if there was not.

Claim 17

A calculator of the digital type including in combination: two factor registers and a working register, each said register having a plurality of orders for storing digital data, each order having (n+1) bits, n of said bits as a group expressing a digit, means for entering said digital data in said registers, means for storing a radix point in each register as a predetermined binary value in the remaining bit of the order in which there is stored the digit associated with said radix point, means for performing a multiplication of the data in a first of said factor registers by the data in the second of said factor registers, partial products being developed in said working register, means to transfer said partial products to said first factor register during said multiplication, first means sensing values in the remaining bits in said first factor register to determine the location of said radix point relative to the data therein, second sensing means responsive to the location of the radix point in the second factor register, means responsive to said first sensing means and operable to enter said predetermined binary value as a marker in the remaining bit of a selected order of said first factor register, said order selection being controlled by said second sensing means, and means responsive to the sensing of said marker by said first sensing means and operable to store said predetermined binary value in a particular order of said first factor register, to place thereby a true radix point in proper relation to said transferred partial product.

Claim 18

A calculator of the digital type including in combination: two factor registers and a working register, each said register having a plurality of orders for storing digital data, each order having (n+1) bits, n of said bits as a group expressing a digit, means for entering said digital data in said registers, means for storing a radix point in each register as a predetermined binary value in the remaining bit of the order in which there is stored the digit associated with said radix point, means for performing a multiplication of the data in a first of said factor registers by the data in the second of said factor registers, partial products being developed in said working register, means to transfer said partial products to said first factor register during said multiplication, first means sensing values in the remaining bits in said first factor register to determine the location of said radix point relative to the data therein, second sensing means responsive to the location of the radix point in the second factor register, means responsive to said first sensing means and operable to enter said predetermined binary value as a marker in the remaining bit of a selected order of said first factor register, said order selection being controlled by said second sensing means, and means responsive to the sensing of said marker by said first sensing means and operable to store said predetermined binary value in a particular order of said first factor register, to place thereby a true radix point in proper relation to said transferred partial product.

Claim 19

A calculator as defined in claim 15, wherein said multiplication means include means for shifting the contents of said working register and first factor register, and said first sensing means comprise gating which passes a first signal upon sensing that said predetermined value has been shifted into the remaining bit of a given order of the first factor register, said marker entry means being responsive to said first signal and effective to enter said marker in the remaining bit of An order identical to that order wherein a radix point is stored in said second factor register; said gating passes a second signal when the marker is in turn shifted into the remaining bit of the given order; and said true radix point storing means is responsive to the second signal.

Claim 20

A calculator as defined in claim 16, wherein said given order is the least significant order of the first factor register and said particular order is the most significant order of that register.

Claim 21

A calculator as defined in claim 15, and further including means to erase said marker in response to sensing thereof by said first sensing means.

Claim 22

A calculator of the binary-coded decimal type including in combination: a set of digit keys, a decimal point key, a multiplication key, and an ''''equals'''' key, a keyboard register, a working register and a factor register, each of said registers having first and second ends and containing a plurality of orders for storing digits, each order having five binary bits, four bits of which are used to express a decimal coded digit, means responsive to a pressed digit key to enter the corresponding binary code in the keyboard register, means for entering a decimal point in the keyboard register upon pressing the decimal point key subsequent to entry of any one digit of a number, the decimal point being entered as a predetermined binary value in the fifth bit of the keyboard register order where said one digit is stored, means for transferring a first-entered number from the keyboard register to the factor register upon depression of the multiplication key, whereby a second number can be entered in the keyboard register while the first-entered number is stored in the factor register, means for coupling the working register as an extension to the keyboard register, means for performing a multiplication upon depression of the ''''equals'''' key, comprising successive additions of the factor register contents to the working register contents according to the value of the digit at one extreme in the keyboard register, then shifting the contents of the coupled working and keyboard registers by one order so that the next-to-extreme digit near said first end of the keyboard register becomes a new extreme digit of the keyboard register, and the corresponding extreme digit in the working register enters an order at said second end of the keyboard register; and again performing additions of the factor register to the working register, as before, governed by the value of the new extreme digit of the keyboard register, means for detection of shifting the fifth bit binary value out of the keyboard register, means for inserting said predetermined binary value into the keyboard register as a marker at the fifth bit of the order corresponding to the location of the decimal point in the factor register, said insertion occurring in response to detection of said shifting out, and means for inserting said binary value in the fifth bit of a particular position of the keyboard register as a true decimal point relative to the product, in response to detection of the shifting out of the marker binary value.

Claim 23

A calculator of the binary-coded decimal type including in combination: a set of digit keys, a decimal point key, a multiplication key, and an ''''equals'''' key, a keyboard register, a working register and a factor register, each of said registers having first and second ends and containing a plurality of orders for storing digits, each order having five binary bits, four bits of which are used to express a decimal coded digit, means responsive to a pressed digit key to enter the corresponding binary code in the keyboard register, means for entering a decimal point in the keyboard register upon pressing the decimal point key subsequent to entry of any one digit of a number, the decimal point being entered as a predetermined binary value in the fifth bit of the keyboard register order where said one digit is stored, means for transferring a first-entered number from the keyboard register to the factor register upon depression of the multiplication key, whereby a second number can be entered in the keyboard register while the first-entered number is stored in the factor register, means for coupling the working register as an extension to the keyboard register, means for performing a multiplication upon depression of the ''''equals'''' key, comprising successive additions of the factor register contents to the working register contents according to the value of the digit at one extreme in the keyboard register, then shifting the contents of the coupled working and keyboard registers by one order so that the next-to-extreme digit near said first end of the keyboard register becomes a new extreme digit of the keyboard register, and the corresponding extreme digit in the working register enters an order at said second end of the keyboard register; and again performing additions of the factor register to the working register, as before, governed by the value of the new extreme digit of the keyboard register, means for detection of shifting the fifth bit binary value out of the keyboard register, means for inserting said predetermined binary value into the keyboard register as a marker at the fifth bit of the order corresponding to the location of the decimal point in the factor register, said insertion occurring in response to detection of said shifting out, and means for inserting said binary value in the fifth bit of a particular position of the keyboard register as a true decimal point relative to the product, in response to detection of the shifting out of the marker binary value.

Claim 24

A calculator as defined in claim 19, wherein said first and second ends are right and left ends, respectively, and said additions depend on the value of the digit at the extreme right in said keyboard register, said shifting occurs to the right, said marker insertion is made when the original keyboard register decimal point has just been shifted out to the right, and said particular position for insertion of the true decimal point is the extreme left digit poisition of the keyboard register.

Claim 25

A calculator of the binary-coded decimal type including in combination: a set of digit keys, a decimal point key, a division key, and an ''''equals'''' key, a keyboard register, a working register and a factor register, each of said registers having right and left ends and containing a plurality of dIgit storage orders, each order having five binary bits, four bits of which are used to express a decimal coded digit, means responsive to a pressed digit key to enter a corresponding binary code in the keyboard register, means for entering a decimal point in the keyboard register upon pressing the decimal point key subsequent to entry of any one of the digits of a number, the decimal point being entered as a ''''1'''' in the fifth bit of the order where said one digit is stored, means for transferring a first-entered number from the keyboard register to the factor register upon depression of the division key, whereby a second number can be entered upon the keyboard register while the first-entered number is stored in the factor register, means for interchanging the factor and keyboard registers upon pressing the ''''equals'''' key after entering said second number when performing division, said interchange placing the dividend in the keyboard register and the divisor in the factor register, means for coupling the working register as an extension to the left of the keyboard register, means for performing a division after said interchange comprising successive subtractions of the factor register contents from the working register contents whenever and for as long as the number in the working register is greater than the number in the factor register and entering the number of such subtractions at the extreme right of the keyboard register, then shifting the coupled registers to the left and repeating the process to generate successive quotient digits, there being at least as many left shifts as there are orders in the keyboard register, means for detecting of the shifting of the fifth bit binary value out of the keyboard register upon a said left shift, means for inserting said predetermined binary value as a marker in the fifth bit of the extreme right order of the keyboard register in response to detection of said shifting out, means providing a signal upon sensing that the marker is in corresponding to the location of the decimal point in the factor register, means responsive to said signal and effective to erase the inserted marker, and to insert a true decimal point in the fifth bit of a particular position of the keyboard register.

Claim 26

A calculator of the binary-coded decimal type including in combination: a set of digit keys, a decimal point key, a division key, and an ''''equals'''' key, a keyboard register, a working register and a factor register, each of said registers having right and left ends and containing a plurality of dIgit storage orders, each order having five binary bits, four bits of which are used to express a decimal coded digit, means responsive to a pressed digit key to enter a corresponding binary code in the keyboard register, means for entering a decimal point in the keyboard register upon pressing the decimal point key subsequent to entry of any one of the digits of a number, the decimal point being entered as a ''''1'''' in the fifth bit of the order where said one digit is stored, means for transferring a first-entered number from the keyboard register to the factor register upon depression of the division key, whereby a second number can be entered upon the keyboard register while the first-entered number is stored in the factor register, means for interchanging the factor and keyboard registers upon pressing the ''''equals'''' key after entering said second number when performing division, said interchange placing the dividend in the keyboard register and the divisor in the factor register, means for coupling the working register as an extension to the left of the keyboard register, means for performing a division after said interchange comprising successive subtractions of the factor register contents from the working register contents whenever and for as long as the number in the working register is greater than the number in the factor register and entering the number of such subtractions at the extreme right of the keyboard register, then shifting the coupled registers to the left and repeating the process to generate successive quotient digits, there being at least as many left shifts as there are orders in the keyboard register, means for detecting of the shifting of the fifth bit binary value out of the keyboard register upon a said left shift, means for inserting said predetermined binary value as a marker in the fifth bit of the extreme right order of the keyboard register in response to detection of said shifting out, means providing a signal upon sensing that the marker is in corresponding to the location of the decimal point in the factor register, means responsive to said signal and effective to erase the inserted marker, and to insert a true decimal point in the fifth bit of a particular position of the keyboard register.

Claim 27

A calculator as defined in claim 21, wherein said marker inserting means insert additional markers in said extreme right order of the keyboard register at every left shift subsequent to said shift out controlled insertion, said sensing-means are responsive to detecting that the first marker has reached the same location as the decimal point in the factor register, and said erasing means remove all the inserted markers except the latest one inserted in response to detection by said sensing means that said first marker is in the order corresponding to the location of the demical point in the factor register and means responsive to the bits of information stored in the keyboard register orders, including said fifth but, subsequent to said removal of all but one marker and effective for displaying the final quotient with the decimal point properly located in the display.

Claim 28

A calculator of the binary-coded decimal type including in combination: a set of digit keys, a decimal point key, and a pair of function keys for controlling addition and subtraction, a keyboard register and a working register, each of said registers containing a plurality of digit storage orders and each order having five binary bits, four bits of which are used to express a decimal coded digit, means responsive to depressions of a digit key to enter a corresponding code in the keyboard register, means for entering a decimal point in the keyboard register upon pressing the decimal point key subsequent to entry of any one of the digits of a number, the decimal point being entered as a ''''1'''' in the fifth bit of the keyboard register order where said one digit is stored, means operable in response to depression of either one of said pair of function keys and automatically aligning each newly entered number in the keyboard register with a previously-entered number in the working register so that their decimal points are in the same location, by shifting one of the two numbers if they are not so aligned upon entry of the newly entered number, means operable subsequent to said alignment and combining the number from the keyboard register albegraically with whatever number is in the working register upon depression of either of said pair of function keys said combination producing a result with proper sign, said sign being determined in part by whether said newly-entered number was followed by depression of the function key controlling addition or that key controlling subtraction, but with said result having false codes for each digit thereof, and said combining means comprising means for carrying and borrowing between the fourth bit of any one order and the first bit of the next higher order, said carrying and borrowing being effected through the fifth bit of said one order and a binary value being recorded in said fifth bit as an expression of said carry or borrow, means for correction of the false coded digit in each order of the working register after an addition or subtraction, according to whether said combination resulted in a carry or borrow in the respective order and the binary value expression in the fifth bit of the respect order, and means responsive to the fifth bit information in said keyboard register for recording identical information in the fifth bits of said working register subsequent to correction of said falsely coded digits.

Claim 29

A calculator of the binary-coded decimal type including in combination: a set of digit keys, a decimal point key, and a pair of function keys for controlling addition and subtraction, a keyboard register and a working register, each of said registers containing a plurality of digit storage orders and each order having five binary bits, four bits of which are used to express a decimal coded digit, means responsive to depressions of a digit key to enter a corresponding code in the keyboard register, means for entering a decimal point in the keyboard register upon pressing the decimal point key subsequent to entry of any one of the digits of a number, the decimal point being entered as a ''''1'''' in the fifth bit of the keyboard register order where said one digit is stored, means operable in response to depression of either one of said pair of function keys and automatically aligning each newly entered number in the keyboard register with a previously-entered number in the working register so that their decimal points are in the same location, by shifting one of the two numbers if they are not so aligned upon entry of the newly entered number, means operable subsequent to said alignment and combining the number from the keyboard register albegraically with whatever number is in the working register upon depression of either of said pair of function keys said combination producing a result with proper sign, said sign being determined in part by whether said newly-entered number was followed by depression of the function key controlling addition or that key controlling subtraction, but with said result having false codes for each digit thereof, and said combining means comprising means for carrying and borrowing between the fourth bit of any one order and the first bit of the next higher order, said carrying and borrowing being effected through the fifth bit of said one order and a binary value being recorded in said fifth bit as an expression of said carry or borrow, means for correction of the false coded digit in each order of the working register after an addition or subtraction, according to whether said combination resulted in a carry or borrow in the respective order and the binary value expression in the fifth bit of the respect order, and means responsive to the fifth bit information in said keyboard register for recording identical information in the fifth bits of said working register subsequent to correction of said falsely coded digits.

Claim 30

A calculator as defined in claim 23, further including a totaling key and an accumulator register, means for transferring to the accumulator register the number appearing in the working register after correction and insertion of the decimal point information, means for copying the number in the accumulator register into the working register, and means actuated upon pressing the totaling key for transferring the sum from the working register to the keyboard register, and displaying the algebraic sum.

Claim 31

A calculator of the digital type including in combination: a pair of data registers, each having a plurality of orders for storing digital data, each order having n + 1 bits, n of said bits as a group expressing a digit and including a least significant bit and a most significant bit, means for performing arithmetic operations on the data in said pair of registers, said operations involving interdigit carries or borrows and the results of said operations being stored in a particular one of said pair of registers in the form of false n-bit groups for each digit, and said arithmetic operations means comprise means for performing said interdigit carries or borrows through the remaining bit of each order, said carry or borrow being effective between the most significant bit of the digit in any one order and the least significant bit of the digit in the next higher order, and for recording said carry or borrow as a binary value in said remaining bit of said one order, and means for correcting each false n-bit group after a said arithmetic operation, according to the value in the remaining bit of each order in said particular register.

Claim 32

A calculator of the digital type including in combination: a pair of data registers, each having a plurality of orders for storing digital data, each order having n + 1 bits, n of said bits as a group expressing a digit and including a least significant bit and a most significant bit, means for performing arithmetic operations on the data in said pair of registers, said operations involving interdigit carries or borrows and the results of said operations being stored in a particular one of said pair of registers in the form of false n-bit groups for each digit, and said arithmetic operations means comprise means for performing said interdigit carries or borrows through the remaining bit of each order, said carry or borrow being effective between the most significant bit of the digit in any one order and the least significant bit of the digit in the next higher order, and for recording said carry or borrow as a binary value in said remaining bit of said one order, and means for correcting each false n-bit group after a said arithmetic operation, according to the value in the remaining bit of each order in said particular register.

Claim 33

A calculator as defined in claim 25 wherein said remaining bit is the most significant in a sequence of (n+ 1) bits.

Claim 34

A calculator as defined in claim 26, wherein said calculator is of the binary-coded decimal type, each order of said registers comprising five binary bits, four bits of which are used to express a decimal digit, and said interdigit carry or borrow being recorded as a predetermined binary value in the fifth bit.

Claim 35

A calculator as defined in claim 27, wherein the binary-coded digits are stored in excess-three code, and said correction means comprise means enablEd during addition, and operable to add a three to a said false n-bit group if there was an interdigit carry and for subtracting a three if there was not.

Claim 36

A calculator as defined in claim 27, wherein the binary-coded digits are stored in excess-three code, and said correction means comprise means enabled during subtraction, and operable to subtract a three to a said false n-bit group if there was an interdigit borrow and for adding a three if there was not.

Claim 37

A calculator as defined in claim 27, wherein said means for performing said interdigit carries or borrows further include means enabled during an addition and storing a particular one of the binary values in said fifth bit position of a respective order if there was a carry from that order, and the other of said binary values if there was not; and means enabled during subtraction and storing the other binary value in said fifth bit of a respective order if there was a borrow propagated from that order, and the particular binary value if there was not.

Claim 38

A calculator as defined in claim 27, wherein said means for performing said interdigit carries or borrows further include means enabled during an addition and storing a ''''1'''' in said fifth bit of a respective order if there was a carry from that order, and a ''''0'''' if there was not; and means enabled during a subtraction and storing a ''''0'''' in said fifth bit of a respective order if there was a borrow propagated from that order, and a ''''1'''' if there was not.

Claim 39

In a calculator of the binary-coded decimal type, the combination of a keyboard having digit keys, a decimal point key, and a set of function keys, a pair of factor registers and a working register, each of said registers having a plurality of orders for storing digits and each order having (n + 1) bits, n of said bits being used to express a decimal coded digit, means to enter a binary value in the remaining one of said bits at a respective order of each said register to represent respective decimal point information, means for performing arithmetic operations on the data in a pair of said registers, the arithmetic operations being effected with said working register, and the results being placed in one of said pair of registers with displacement of the data therein, means responsive to the displaced decimal point information of said one register and operable to enter said binary value as a marker in the remaining one bit at a particular order of the one register, means for detecting appearance of said marker in a discrete order of said one register upon said displacement, and means operable to enter said binary value in the remaining one bit at a selected order of said one register as the true decimal point relative to the results placed in said one register in response to said means detecting appearance of the marker.

Claim 40

In a calculator of the binary-coded decimal type, the combination of a keyboard having digit keys, a decimal point key, and a set of function keys, a pair of factor registers and a working register, each of said registers having a plurality of orders for storing digits and each order having (n + 1) bits, n of said bits being used to express a decimal coded digit, means to enter a binary value in the remaining one of said bits at a respective order of each said register to represent respective decimal point information, means for performing arithmetic operations on the data in a pair of said registers, the arithmetic operations being effected with said working register, and the results being placed in one of said pair of registers with displacement of the data therein, means responsive to the displaced decimal point information of said one register and operable to enter said binary value as a marker in the remaining one bit at a particular order of the one register, means for detecting appearance of said marker in a discrete order of said one register upon said displacement, and means operable to enter said binary value in the remaining one bit at a selected order of said one register as the true decimal point relative to the results placed in said one register in response to said means detecting appearance of the marker.

Claim 41

A calculator is defined in claim 32, wherein each register has first and second ends, the working register and said one register are coupled to form a single register, the arithmetic operation is a multiplication, partial products being developed by repeat addition of the contents of the other of said pair of registers to the contents of said working register according to the value of successive digits in said one register, the partial product corresponding to each digit being successively shifted by one order into said one register with simultaneous displacement of the information therein; said means responsive to the decimal point in the one register comprise means to detect a first appearance of said binary value in the remaining one bit of a first end order of said one register and means responsive to said detection and operable to enter said binary value as the marker in the remaining one bit at an ordinal position of the one register corresponding to the ordinal position of the decimal point in said other register; said means to detect said marker and enter the trUe decimal point comprise means defining detection of a second appearance of said binary value in the remaining one bit of said first end order of the one register, and said selected order is the second end order of said one register.

Claim 42

A calculator is defined in claim 33, said orders further including a rightmost and a leftmost order, and wherein there are five bit positions per order, said decimal point information being stored as a ''''1'''' in the fifth bit, and said first end order and second end order are the rightmost and leftmost orders of the one register, respectively.

Claim 43

A calculator as defined in claim 32, said orders further including a right most order and wherein the working register and said one register are coupled to form a single register; the arithmetic operation is division, quotient digits being developed by counting the number of successful subtractions of the contents of the other of said pair of registers from the contents of said working register as the contents of said one register are left-shifted into the working register one order at a time, each said quotient digit being stored in the rightmost order of the one register, vacated on each shift; said means responsive to the decimal point in the one register comprise means responsive to left-shifting of said binary value of the one register into the rightmost order of the working register and operable to enter said binary value as a marker in the remaining one bit of said rightmost order of the one register; said marker detection means are responsive to the left-shifting of the marker into the remaining one bit of an order of the one register corresponding to the order of the other register having the binary value stored in the remaining one bit thereof; and the true decimal point entering means are operable to enter the binary value in the remaining one bit of the rightmost order of the one register and to remove the marker.

Claim 44

A calculator as defined in claim 35, wherein there are five bits per order, said decimal point information being stored as a ''''1'''' in the fifth bit.