There is a program called TELNET to get to another CPU. Control up-arrow is the escape; it's doubled to send it through, and "quit" is control up-arrow Q.
A hacker once used TELNET to get to another CPU. He knew he could quit whenever he wanted to: all he had to do was type control up-arrow Q.
Instead the hacker used TEL-NET to get to another CPU. He knew he could quit whenever he wanted to: all he had to do was type control up-arrow [at i-th time, repeat 2^i times] Q. [repeat verse n times; the choice of n is free]
The hacker soon got bored with this, and wanted to get back. He sighed, and started the exponential popping of the stack:
The hacked flushed the TEL-NET to the most distant CPU: He couldn't log out until he had killed them all, counting up powers of two: he typed control up-arrow [at i-th time, repeat 2^(n-i+1) times] Q. [repeat n times]
The hacker's eyes were bloodshot; his fingers, black and blue; He wanted to log out and and go home to bed, and sleep for a day or two. He typed L O G O U T ... carriage return ...
The hacker was on a network with only twenty CPU's. But if he had telnetted to them all, he would not yet be through with typing control up-arrow [repeat 7 times] Q!
Author : Guy L. Steele / D.E. Knuth