For integers, there is a uniquely defined next integer with no integers in between. Next(5) is 6, Next(-3) is -2.

What is Next(0x7fff ffff)? or in decimal, Next(2147483647)?
Next(0x7fffffff) is 0x80000000 or equivalently in decimal,
Next(2147483647) is -2147483648.

What about real numbers? Is there a next real number after 3.141?

No, but given a C float value, there is a next larger float value (except for the special values).

What should s, exp, and frac be to get the value 8.0 and the next value after 8.0?

What should s, exp, and frac be to the value 1024.0 and the next float value after 1024.0?