1. xerox 560 computer system - The UK Mirror Service

again present, unti I a positive or negative sign isencountered, or unti I the destination byte stringis entirely processed, whichever occurs first.d. The destination byte string is entirely processed,in which case the basic processor executes thenext instruction in sequence.Detai led operation of EDIT BYTE STRING follows. Theexplanation is necessari Iy quite detailed due to the highdegree of flexibi lity inherent in EBS. Condition codesettings are made continuously during the editing processand these settings help determine how each subsequent patternbyte will be edited. The summary of condition codesettings given later in this section wi II help clarify thefollowing discussion:1. If the count in bit position 0-7 of register R+l is anonzero, a pattern byte is obtained from the destinationbyte string; if the count in register R+l is 0,the basi c processor executes the next instruction insequence.2. If the pattern byte is a digit selector (X'20'), a significancestart (X'211), or immediate significancestart (X'23 1 ), a digit is accessed from the decimalinformation field as follows:a. A decimal byte is obtained from the byte locationpointed to by the displacement in EBS plus thesource address in register R.b. If bits 0-3 of the decimal byte are a sign code,the basi c processor auto mati ca lIy aborts executi onor EBS ana traps ro iocarion X;45;, wlrh the contentsof register R, register R+l, the conditioncode, and the destination byte string unchangedfrom their current contents.c. If CC2 is currently set to 0, the digit to be usedfor editing is the left digit (bits 0-3) of the decimalbyte; however, if CC2 is currently set to 1,the digit to be used is the right digit (bits 4-7)of the decimal byte. In either case, CC3 is setto 1 if the digit is nonzero. If CC2 is set to 1and the right digit (bits 4-7) of the decimal byteis a sign code, the basic processor automaticallyaborts execution of EBS and traps to location X'45 1 ,as described above.d. One of the following editing actions is performed:ConditionsActionMarkConditions Action MarkPattern byte=S S (X 1211)CC4=l (cont.)(because CC4= 1 meanssignificance alreadyencountered}.Pattern byte=SS Expand digit to zoned Mode 1CC4--oformat, store in patnonzerodigittern byte location(because nonzero digitbegins significance),and set CC4 to 1.Pattern byte=SS Store fi II character in Mode 2CC4--opattern byte locationdigit=O(because significancestarts with next patternbyte) and setCC4 to 1.Pattern byte=DS(X'20'} Expand digit to zoned NoneCC4=lformat, and storedigit in pattern bytelocation.Pattern byte=DS Expand digit to zoned Mode 1CC4=Oformat, store digit innonzero digitpattern byte location,and set CC4 to 1 tosignal significance.Pattern byte=DS Store fi II character in NoneCC4=Opattern byte locati ondigit=O(because significancenot encountered yet).e. If CC2 is currently reset to 0 and if bits 4-7 ofthe decimal byte are a positive decimal sign code,CCl is set to 1, CC4 is reset to 0, and the sourceaddress in register R is incremented by 1. If CC2is currently reset to 0 and if bits 4-7 of the decimalbyte are a negative decimal sign code, CCland CC4 are both set to 1, and the source addressis incremented by 1. Otherwise, CC2 is addedto the source address and then CC2 is inverted.f. If marking is invoked at set d, above, one of thetwo following marking operations are performed:Mode 1: Load bits 13-31 of register R+l into bitpositions 13-31 of register 1; bit positions0-12 of register are unpredictable.Pattern byte=SI(X '23 1 )Expand digit to zonedformat, store in patternbyte locati on,and set CC4 to 1 (startsignificance).Mode 1Mode 2: Load bits 13-31 of register R+l into bitpositions 13-31 of register 1 and thenincrement the contents of register 1by 1; bit positions 0-12 of register 1 areunpredictable.Pattern byte=SS(X'21I)CC4=1Expand digit to zonedformat and store inpattern byte locationNoneIf marking is not applicable (i. e., significancehas not been encountered), the contents of register1 are not affected.Byte-String Instructions 93