I was going through the archives on www.techtales.com, and I came across this one: Punch Card Problems This one really belongs to my dad. Many years ago, he was using a PDP 8 with 8k of core for generating geological maps. All the programmes and data were entered via punch card or paper tape. On one run, it just wouldn't work. All the cards were manually checked, a very labour and time intensive process. Still nothing worked. Eventually, the whole run was repunched card by card and in the end it did work. Some detective work revealed the source of the errors. The dye used in the blue punch cards was slightly hygroscopic. The absorbed water made all the blue cards slightly longer than the rest, just long enough to throw off the reader. The solution: replace all the blue cards....... Thanks to: Araneas -- Love of the Goddess makes the poet go mad he goes to his death and in death is made wise. Robert Graves