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Retrocomputing

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    Indentation matters only when you have multi-statement constructs (compound statements, blocks), and FORTRAN had no such thing in the timeframe under consideration. Maybe you'd want to indent DO-loop bodies for readability, but the end of a loop was indicated by a statement number given after DO, and indentation conveyed no syntactic meaning. Indeed, outside of Hollerith constants, spaces were entirely ignored in columns 7 to 72. Commented Nov 25, 2022 at 14:42
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    It may be relevant to separate intent from fixed column. Commented Nov 25, 2022 at 15:40
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    Maybe it's just me, but I would not use the word "indentation" to describe a requirement that certain things appear in certain columns of a punched card. I used both card-based systems and on-line/teleprinter-based systems back in the 1970s, and my recollection is each had its own nomenclature with not much overlap between them. Commented Nov 26, 2022 at 23:21
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    Me neither. The acid test for me is, within the range of columns allowed for a statement, does the number of leading spaces change the semantics of the statement? For FORTRAN and COBOL (of that time), the answer is "no". Commented Nov 27, 2022 at 2:01
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    @psmears qq{Isn't "requiring a statement to begin in column N" more or less the same thing as saying that indentation is significant?} Well... no, IMHO. Not any more than respecting the left margin of the page when writing a text document is "indentation". Columns 1-6 and 73+ are effectively the card's margins. Commented Nov 28, 2022 at 19:37