IBM 610 Manual Of Operation

Also see for 610: Technical overview and introduction

20 B M 6 10PROGRAM TAPEThere are many occasions when it is desirable toprocess several sets of data for the same problem insome automatic manner. One method of doing thisis by using the Program Tape Reader.While the operator is working a problem for thefirst time, he may set switches on the keyboard thatcause the machine to punch codes into a paper tapeequivalent to the keys being depressed. Later he may,by changing switch settings and depressing appro-priate keys, turn over control of the machine to thisprogram tape. The only activity required of theoperator when the program tape is being used willbe the entering of new sets of data into the machineduring the processing of each problem.In order to get the program into the tape duringthe processing of the first set of data, the operatorsimply sets the punch switch on the keyboard to theON position. A full discussion of the switches andlights on the keyboard will be found in a later section.The operator now proceeds in a manner similar tothe one-time calculation. He must always be cog-nizant of the source of the data. The only differencewill be that the program tape punch is active. At theend of the processing of the first calculation, theprogram is entirely punched into the tape and thetape is accumulated (up to fifty feet) in the machine.Now the operator is ready to allow the programtape to take over control of the machine. He firstturns off the punch switch and turns on the dupswitch. The dup switch causes the code symbols readby the program tape reader to be duplicated back intoprogram tape that is passing by the program tapepunch. The program tape thus continuously recreatesitself sequentially so that it may be used again andagain. The program tape is placed in control of themachine by depressing the ptr key.®(Program Tape Reader)The depression of this key tells the machine to turncontrol over to the instructions punched into the pro-gram tape, which is standing ready to be read at theProgram Tape Reader. The first character encoun-tered by the reader will be the first step in the pro-gram to be executed.TkB J (Keyboard)When the 610 is under the control of the programtape unit, it may be necessary to give an instructionto return control to the keyboard.This instruction causes control of the machine tobe transferred from the unit in control to the key-board. One use of this instruction is to return controlfrom the program tape reader to the keyboard for theentry of data. An instruction sequence 05 ent kbwill cause the machine to transfer control to the key-board for data entry. After the number has been en-tered, depressing ptr will return control to the pro-gram tape reader.Instruction ClassesIn many problems, it may be necessary to chooseone of several possible methods of solution after somepoint in the calculation, depending on conditionsgenerated up to that point.For example, in the calculation of the roots of aquadratic equation (previously used example), it ispossible that the discriminant (b^ - 4ac) may benegative. If the discriminant is negative, the roots ofthe quadratic equation will be complex numbers andit will be necessary to separate the real and imaginaryparts for printing. The possibility of having complexroots was not considered in our previous example.In solving for the roots of a series of such equa-tions, it is usually inconvenient to separate by visualinspection the equations having real roots, from theequations having imaginary roots, and then solvethem with separate programs. It would be extremelydesirable to have a program that would solve foreither condition, dependent upon the sign of the dis-criminant. Because all symbols on the program tapemust be read in sequence, a problem is posed havingboth the series of steps for finding the roots of anequation with a positive discriminant and the seriesof steps for finding the roots of an equation with anegative discriminant on the same tape. It would bevery convenient to have the machine make a logicaldecision and use only one series of steps while ignoringthe other. The IBM 610 is able to make such a logicaldecision.