The DO-loop incident did happen at NASA, and at about the same time. As told by Fred Webb in alt.folklore.computers in 1990: | I worked at Nasa during the summer of 1963. The group I was working | in was doing preliminary work on the Mission Control Center computer | systems and programs. My office mate had the job of testing out an | orbit computation program which had been used during the Mercury | flights. Running some test data with known answers through it, he was | getting answers that were close, but not accurate enough. So, he | started looking for numerical problems in the algorithm, checking to | make sure his tests data was really correct, etc. | | After a couple of weeks with no results, he came across a DO | statement, in the form: | DO 10 I=1.10 | This statement was interpreted by the compiler (correctly) as: | DO10I = 1.10 | The programmer had clearly intended: | DO 10 I = 1, 10 | | After changing the `.' to a `,' the program results were correct to | the desired accuracy. Apparently, the program's answers had been | "good enough" for the sub-orbital Mercury flights, so no one suspected | a bug until they tried to get greater accuracy, in anticipation of | later orbital and moon flights. As far as I know, this particular bug | was never blamed for any actual failure of a space flight, but the | other details here seem close enough that I'm sure this incident is the | source of the DO story. Project Mercury's sub-orbital flights were in 1961, and its orbital flights began in 1962. I forwarded the above to comp.risks, slightly abridged, and it appeared there in issue 9.54.