Special variables: Difference between revisions

Fortran offers no special variables such as Pi, e, etc. as a part of the language, not even the modern special floating-point "values" such as NaN. Indeed, the syntax has no reserved words generally so that <code>GOTO</code> could be a variable without damage to GO TO statements. It does have some numbers that are special: 5 is the input/output "unit number" for keyboard input and 6 for output to "standard output", the screen on desktop computers; in the past there have been other values that were associated to devices such as the card reader, card punch, lineprinter, paper tape reader, and so on at any given installation. But these constants are not given names as mnemonics for their special values, except by the programmer.