Fortran 77 中的“X”和“Z”在表示十六进制时的差异

Question

I am working on some legacy code. I saw two kinds of Integers:

z'ffffffff' and 'ffffffff'x

from https://docs.oracle.com/cd/E19957-01/805-4939/c4000413626f/index.html X or Z are for hexadecimal. So what's the difference between z'ffffffff' and 'ffffffff'x ?

Answer 1

Both were accepted as compiler extensions by the (pre-Fortran 90) compiler that was used to compile your code.

In Fortran 90 and later only the z'0000' syntax is allowed. The standard revision differ in the context where exactly they are allowed to be placed.

The '0000'x is completely non-standard.