Long ago I learned Programming in FORTRAN. I got used to the convention that names starting with I,J,K,L,M,N were INTEGER while all other letters were REAL. I thought it was a convention of FORTRAN only. Since then, I came to realize that the same convention is widely used in science and math independent of computer programming. But I do not recall ever being explicitly taught any such convention. My question: what is the origin of this convention? I'm posting it here under math as a guess as to the right forum. P.s Wikipedia mentions this convention under "naming conventions (programming)", but it does not mention the origin.