The
tradition of using
i as a "
meaningful"
integer index started with the
implicit variable naming
technique employed in old
Fortran 77 compilers. Fortran 77 implicitly casted any
variable name starting with any
letter between
i through
n as an integer. Variables that started with other letters were not cast as integers. Implicit
type casting is
bad coding practice.
(Don't use
n for integers for the sole reason that Fortran 77 uses it. Use
n because your
math book uses it.)
You still have to explicitly declare variables that start with i-n (or any other letter) as an integer before using it in languages like C/C++. That's explicit type casting and C/C++ enforces strong type casting, so it's good coding practice.