LISP I Programmer's Manual - Software Preservation Group

Ioflex(x) is a predicate which has the value true (T) orfalse (F). If x = READ the predicate asks if the Flexowriteris in the reading (type-in) mode; if x = PRINT the predicateasks if the Flexowriter is in the printing (type-out) mode; andif x is something else an error message followed by F is typedout.1oflip (y) is an operative function which changes controlas follows:y = READflips control between reading fromcards or reading from type-in onthe Flexowritery = PRINTflips control between printing onthe on-line printer or by Flexowritertype-outsy = anything else flips the last pair that was flipped.It assumes initially that this was aREAD.Note At certain times the LISP-Flexo System may hang up tryingto read the card reader. How it gets into this trouble, andhow to get out of it are described below.An input of the form IOFLIP, (READ),() given when operatingin the Flexowriter type-in control will select the cardreader and cause the read program to try to read in cards containinglists of triplets. If no cards of this form are inthe reader, andp EOF (end-of-file) error from the read programoccurs, and the card reader is selected again. The card readerwill not be in ready status, and if the START button on thecard reader is selected another EOF error will occur. To getout of this cycle one can type a tab on the Flexowriter. Thetab will not be processed, but the Flexowriter keyboard willlock. At this point, pressing the START button on the cardreader will get the 704 back on the line so that the interrupt