IBM 610 Manual Of Operation

Also see for 610: Technical overview and introduction

CONTROL DEVICES 21In order to provide for a logical decision while pro-ducing a program tape, the operator may punch eachinstruction in any one of four classes (0, 1, 2, 3) byturning on the appropriate punch class switch. Theoperator will punch the program for two alternateprocesses in consecutive order in, say, classes 1 and 2.The main program is usually punched in class 0.In the event that the first of the two alternatives ischosen, the 610 will be set to respond to class and 1instructions.The class 1 instructions would logically be readfirst; and if the machine is set to respond to that class,the data is processed by that portion of the program.The program tape reader next encounters the instruc-tions punched in class 2. Because the machine hasbeen set to respond to only classes and 1, the ma-chine reads (and duplicates) but does not respondto class 2 instructions and will not re-act to any in-structions until it again reaches class or 1 instruc-tions.If the second of the two alternatives is chosen, the6 1 will be set to respond to class and 2 instructions.The class 1 instructions of the first alternative will beencountered, reproduced (if the dup switch is on),and ignored by the machine. When the machine hasread, reproduced, and ignored the class 1 instructions,it will encounter class 2 instructions. It will read themand process the data. The machine will continue toprocess data according to class and 2 instructionsuntil otherwise instructed. In either case, the IBM 610has made the decision as to which of the two sets ofinstructions to use.Regardless of class response switch settings, if theDUP switch is on during control by the programtape, all instructions will be reproduced. In effect,unused class coded instructions become no opera-tion steps that are used but never executed.Program Tape Response ClassThe program tape punch and reader are eight-channel devices. Of these eight channels, five are usedfor code symbols associated with operation keys, onechannel is used for even-order redundancy check,as described in the Tape Code Section. The remainingtwo channels may be used to record the class markspreviously described, and the computer can be caused• • •• CHANNELS]I— Response Class• •CHAJ«)NEL7j ch^iels• • CHANNEL 6 — Even Count• •CHANNEL 1CHANNEL 2• • • •CHANNELSCHANNEL 4I CHANNELS_1Redundancy— Five Channel*for Numbersand CodesCM mu oouV^ (Mo ouS a g. o -rS a -So-•fl >< -3 8 MOB. a sSO 3 -3 j-I" °"o -3 a -2 o"Figure 7. Tape Response Classesto obey or ignore any given instruction code symboldepending upon its class mark and the positioning ofthe response class switches (Figure 7).In the group of switches on the keyboard control-ling the program tape operation is a set of threeswitches labeled punch class. Normally, all theseswitches are off; and, if the program punch switchis on, the program tape punch records code symbolsin the tape, leaving the channels 7 and 8 unpunched.The program is said to be recorded in class 0. If theswitch labeled I is turned on, the same channels arepunched for a code symbol, but in addition, the sev-enth channel is punched. If switch 2 is on, the samechannels are punched for a code symbol, but in addi-tion, the eighth channel is punched. If switch 3 is on,the same code channels are punched, but in addition,both channels seven and eight are punched.When the control of the machine is turned over tothe program tape reader, the operator may set theresponse class switches to classes 0, 1, 2 or 3. If theswitch is on, the machine responds to all instruc-tions with no punches in channels 7 and 8. If theswitch is off, the machine will not respond to theseinstructions. In a similar manner, the switches maybe set to respond to classes 1, 2 or 3 or any combina-tion.