IBM 610 Manual Of Operation

Also see for 610: Technical overview and introduction

60 IBM 6 10The PROGRAM STEP lights indicate the next pro-gram step to be executed. The left-most column indi-cates the letter prefix of the next program step. Thenext column consisting of three digits (0, 1, and 2)indicates the tens digit of the next program step. Theright-most column of lights indicates the units digitof the next program step. For instance, if A, 1, and 8are illuminated, the next program step to be executedis A- 18. If C is illuminated, zero in the tens columnis illuminated, and 3 in the units is illuminated, pro-gram step C-03 is the next step to be executed.CHECKING FEATURESIn designing the IBM 610 computer, reliability aswell as ease of use was a prime consideration.We have explained those checking features thatare brought to the attention of the operator. Thesechecking features plus the inherent conservative de-sign of the computer make for an unusually reliablemachine.In addition to these checking features, listeid beloware the self-checking features within the machine:1. Each time a character is punched into, or readfrom, the paper tape, the character is checked to becertain it is represented by a valid code.2. Whenever numbers are moved within the 610,all digits are checked for valid coding.3.Arithmetic operations are checked to verify thatthe sum, product, or quotient does not exceed themaximum allowable quantity.4. Many arithmetic operations require clearing ofa register. Each clearing operation is checked to in-sure that every position of the register is set to zeroand that the arithmetic unit is functioning properly.5. Every time the electronic computer operates,a check is made to insure that the attention of themachine is directed to a permissible register.