1. xerox 560 computer system - The UK Mirror Service

••••Contents of register R:Contents of register R+l:(and only one) of the following actions with the pattern byteand the decimal digit:1. The fi II character (contents of bit positions 0-7 of registerR) or a blank character replaces the byte in thedestination byte string.2. The decimal digit is expanded to zoned decimal format'and replaces the pattern byte in the destination bytestring.The destination byte string is an editing pattern that beginsin the byte location pointed to by the destination addressin register R + 1, and is C bytes in length. The decimalinformation field, which must be in packed decimal format,begins with the byte location pointed to by the displacementin EBS plus the source address in register R. The decimalinformation field must contain legal decimal digit andsign codes (packed format) and must begin with a decimaldigit.The destination byte string (the editing pattern) may containany 8-bit codes desired. However, four byte codesin the editing pattern have special meanings. These codesare as follows:Binary value Function Abbrevi ati on0010 0000 (X'20 ') Digit selector ds0010 0001 (X'211) Signifi cance start ss0010 0010 (X'221) Field separation fs0010 0011 (X'23 1 ) Immediate signifi- sicance startBefore executing EBS, the condition code should be sett" • _____ MOO if •• tho 1.1- hi"h ..........Io .. ...Ii"a .... f tho ...Io,...;m,.,1 ..... mho .. ;., i ....".~ _. __ • _.~ _ ••••____•••• _ ••• _ ••• ....,_..... IIIthe left half of a byte, and should be set to 0100 if thehigh-order digit is in the right half of a byte.The editing operation performed on each pattern byte ofthe destination byte string is determined by the followingcondi tions:1. The pattern byte obtained from the destination bytestring.2. The decimal digit obtained from the decimal numberfield.3. The current state of the condition code.Depending upon various combinations of these conditions'the instruction EDIT BYTE STRING performs one3. The pattern byte remains unchanged.In general, the normal editing process is as follows:1. Each byte of the destination byte string is replaced bya fi II character until significance is present, either inthe destination byte string or in the decimal informationfield. Significance is indicated by any of thefollowing:a. The pattern byte is X' 23 1 (immediate significancestart), which begins significance with the currentdecimal digit.b. The pattern byte is X' 21 1 (significance start),which begins significance with the following patternbyte.c. The current decimal digit is nonzero, which beginssignifi cance with the current pattern byte.2. After significance is encountered, each pattern bytethat is X' 20' (digit selector), X' 21 1(significance start),X'22 1 (field separator), or X' 23 1 (immediate significancestart) is replaced by a zoned decimal numberfrom the decimal field and all other pattern bytes areunchanged. This process continues unti I any of thefollowing conditions occurs:a. A positive sign is encountered in the decimal field,in which case subsequent pattern bytes are replacedby blank characters unti I significance isagain present, unti I a field separator is encountered,or unti I the destination byte string is entirelyprocessed, whichever occurs first.b. A negative sign is encountered in the decimalfield, in which case subsequent pattern bytes areunchanged unti I signifi cance is again present, unti Ia field separator is encountered, or unti I the destinationbyte string is entirely processed, whi cheveroccurs fi rst.c. A pattern byte of X' 22 1 (field separator) is encountered,in which case the field separator is replacedby a fi II character; subsequent pattern bytes are replacedby the fill character until significance is92 Byte-String Instructions