Re: IEFBR14 (was Re: IND$FILE)
On 11/19/2018 5:27 PM, Eric Smith via cctalk wrote: On Mon, Nov 19, 2018 at 2:24 PM Sean Conner via cctalk < cctalk@classiccmp.org> wrote: I've always been amused by IEFBR14 ever since I heard about it. I first came across it by this quote: Every program has at least one bug and can be shortened by at least one instruction---from which, by induction, one can deduce that every program can be reduced to one instruction which doesn't work. IEFBR14 was this program---one instruction long, and it contained a bug: http://en.wikipedia.org/wiki/IEFBR14 By induction you should be able to reduce a program to zero instructions. On CP/M, you actually can, and the resulting program is useful, and as far as I know, has zarro boogs. (Which instruction could a bug be in?) That expains why you never see computers with the single instruction Subtract and branch on condition.
Re: IEFBR14 (was Re: IND$FILE)
On Mon, Nov 19, 2018 at 2:24 PM Sean Conner via cctalk < cctalk@classiccmp.org> wrote: > I've always been amused by IEFBR14 ever since I heard about it. I first > came across it by this quote: > Every program has at least one bug and can be shortened by at least > one instruction---from which, by induction, one can deduce that > every program can be reduced to one instruction which doesn't work. > IEFBR14 was this program---one instruction long, and it contained a bug: > http://en.wikipedia.org/wiki/IEFBR14 > By induction you should be able to reduce a program to zero instructions. On CP/M, you actually can, and the resulting program is useful, and as far as I know, has zarro boogs. (Which instruction could a bug be in?)
IEFBR14 (was Re: IND$FILE)
It was thus said that the Great jim stephens via cctalk once stated: > > IFBR14 if you all are not familiar with MVS / MVT batch programming is a > program which immediately terminates w/o any return codes by doing an > assembly language return to the caller of the job step via the contents > of R14 of the processor, which is also the return address. I've always been amused by IEFBR14 ever since I heard about it. I first came across it by this quote: Every program has at least one bug and can be shortened by at least one instruction---from which, by induction, one can deduce that every program can be reduced to one instruction which doesn't work. IEFBR14 was this program---one instruction long, and it contained a bug: http://en.wikipedia.org/wiki/IEFBR14 -spc (The fix doubled the size of the program---such bloat!)
