List control

Claim 1

IN A DIGITAL DATA PROCESSOR INCLUDING A MEMORY HAVING A PROGRAM STORED IN ADDRESSABLE CELLS WITH ADDRESS CODES N, N+1, N+2, ... X, X+Y, X+Z, ... S, S+1, S+2 ... WHERE N, S, X, Y AND Z ARE ARBITRARY INTEGERS, FOR STORING DATA WORDS, EACH WORD CONSISTING OF A GROUP OF DIGITAL SIGNALS REPRESENTATIVE OF A COMMAND TO BE EXECUTED INCLUDING THE ADDRESS (DIRECT OR INDIRECT) OF AN OPERAND, OR AN OPERAND TO BE PROCESSED, A MEMORY ADDRESS REGISTER FOR RECEIVING AND STORING A GROUP OF DIGITAL SIGNAL REPRESENTING THE ADRESS OF A MEMORY CELL FROM WHICH A DATA WORD IS TO BE READ, A PROGRAM ADDRESS REGISTER FOR STORING A GROUP OF DIGITAL SIGNAL REPRESENTING THE ADDRESS OF THE NEXT COMMAND TO BE EXECUTED, AN ADDRESS MODIFICATION REGISTER ADAPTED TO RECEIVE AN ADDRESS OF AN OPERAND, AND IN CONJUNCTION WITH AN ARITHMETIC UNIT ADDING OR SUBTRACTING A NUMERICAL VALUE FROM SAID ADDRESS, A SEQUENCE CONTROL UNIT FOR CONTROLLING THE OPERATION STATES CALLED FOR BY AN INSTRUCTION BEING EXECUTED AND FOR OBTAINING THE NEXT COMMAND TO BE EXECUTED IN SEQUENCE FROM THE CELL SPECIFIED BY THE CONTENTS OF SAID PROGRAM ADDRESS REGISTER, THE IMPROVEMENT COMPRISING A LIST CONTROL STRUCTURE COMPRISING THREE WORDS STORED IN MEMORY LOCATIONS X,X+Y, AND X+Z, THE WORD IN LOCATION X REPRESENTING A CURRENT ADDRESS WHICH IS THE ADDRESS OF THE OPERAND TO BE OPERATED UPON, THE WORD IN LOCATION X+Y REPRESENTING AN END ADDRESS SPECIFYING THE ADDRESS OF THE LAST OPERAND OF A LIST STORED IN THE MEMORY TO BE OPERATED UPON, AND THE WORD IN LOCATION X+Z REPRESENTING A START ADDRESS SPECIFYING THE ADDRESS OF THE FIRST OPERAND OF SAID LIST OF OPERANDS TO BE OPERATED UPON, SAID START ADDRESS BEING EQUAL TO SAID CURRENT ADDRESS THE FIRST TIME THE LIST CONTROL STRUCTURE IS REFERRED TO BY A COMMAND OF SAID STORED PROGRAM, SAID ADDRESS MODIFICATION REGISTER BEING ADAPTED TO RECEIVE AN ADDRESS FROM THE MEMORY UNDER CONTROL OF SAID SEQUENCE CONTROL UNIT WHEN AN INDIRECT ADDRESS MODE COMMAND IS TRANSFERRED THERETO FROM SAID MEMORY FOR EXECUTION, SAID ADDRESS BEING TAKEN FROM A MEMORY CELL SPECIFIED BY THE ADDRESS PORTION OF THE INDIRECT ADDRESS MODE COMMAND, APPARATUS FOR SENSING THE PRESENCE OF A DIGIT IN A FIRST PREDETERMINED DIGIT POSITION OF THE ADDRESS WHICH, IF TAKEN FROM LOCATION X, IS THE CURRENT ADDRESS OF A LIST CONTROL STRUCTURE, COMPARING APPARATUS RESPONSIVE TO THE PRESENCE OF A DIGIT IN SAID FIRST PREDETERMINED DIGIT POSITION FOR DETERMINING WHETHER SAID CURRENT ADDRESS IS EQUAL TO SAID END ADDRESS READ FROM THE MEMORY CELL X+Y, APPARATUS FOR SIMULTANEOUSLY SENSING THE PRESENCE OF A DIGIT IN A SECOND PREDETERMINED DIGIT POSITION OF SAID CURRENT ADDRESS FOR INTERNAL SEQUENCE CONTROL PURPOSES, AND IN RESPONSE THERETO FOR SUBSTITUTING SAID START ADDRESS FROM THE MEMORY CELL X+Z FOR THE CURRENT ADDRESS IN SAID ADDRESS MODIFICATION REGISTER WHICH START ADDRESS IN SAID REGISTER BECOMES THE CURRENT ADDRESS AND FOR SUBSTITUTING SAID START ADDRESS READ FROM THE MEMORY CELL X+Z FOR THE END ADDRESS OTHERWISE READ FROM LOCATION X+Y, IN THE COMPARISON PERFORMED BY SAID COMPARING APPARATUS, APPARATUS FOR STORING BACK IN SAID MEMORY CELL X THE CURRENT ADDRESS INCREMENTED OR DECREMENTED BY ADDING OR SUBTRACTING A PREDETERMINED NUMBER, SAID CURRENT ADDRESS ALSO BEING RETAINED UNALTERED IN SAID ADDRESS MODIFICATION REGISTER AS THE OPERAND ADDRESS FOR THE INDIRECT ADDRESS MODE COMMAND TO BE EXECUTED REGARDLESS OF WHETHER THE CURRENT ADDRESS IS EQUAL TO SAID END ADDRESS AND FOR SETTING A DIGIT IN SAID SECOND PREDETERMINED DIGIT POSITION OF THE CURRENT ADDRESS AS IT IS INCREMENTED OR DECREMENTED AND RESTORED IF THE CURRENT ADDRESS IS EQUAL TO SAID END ADDRESS, ALL IN RESPONSE TO SAID COMPARING APPARATUS, AND APPARATUS FOR STORING IN SAID MEMORY CELL X THE START ADDRESS INCREMENTED OR DECREMENTED BY ADDING OR SUBTRACTING SAID PREDETERMINED NUMBER IN RESPONSE TO THE AFORESAID SENSING OF A DIGIT IN SAID SECOND PREDETERMINED DIGIT POSITION INSTEAD OF THE CURRENT ADDRESS INCREMENTED OR DECREMENTED AS AFORESAID.