BCD, actually, given that Fortran dates from the mid-1950s. EBCDIC only appeared more or less around Fortran IV, in the early 1960s. Many printers in those days had a 48-character chain/train. After upper-case letters, digits, and a few essential punctuation marks (like . and ,), you weren't left with many options. The 60-character set of PL/I was a luxury back then, let alone lower case.
kragen|3 months ago
But IBM's BCD character sets, including the 48-character ones you allude to, didn't: https://en.wikipedia.org/wiki/BCD_(character_encoding)#Examp... (though Honeywell's did)
There are a lot of decisions in Fortran that stem from the absence of useful characters. .LT., .LE., .EQ., .NE., .GT., and .GE. is another.