From the Wikipedia article on FORTRAN (emphasis mine):
The primary purpose of the DATA statement is to give names to constants; instead of referring to pi as 3.141592653589793 at every appearance, the variable PI can be given that value with a DATA statement and used instead of the longer form of the constant. This also simplifies modifying the program, should the value of pi change.” —Early FORTRAN manual for Xerox Computers
Another thing I learnt from the Wikipedia article was that the arbitrary and somewhat arcane syntax of early versions of FORTRAN was blamed, among other things, for the crash of the Mariner I space probe. It appears to have been merely a tall tale, one that has since been superseded by the much more expensive error of neglecting to convert between English and metric units1 which plagued the NASA expedition to Mars in 1999. It’s not often to witness a software error result in a physical crash, but in this case this bug caused the Mars Climate Orbiter to deorbit and plunk itself on the surface of Mars, resulting in catastrophic failure of the entire Mars mission and wasting a cool $190m in funding.
Footnotes- Not by NASA itself, it seems, but from contracted software written by Lockheed-Martin↩