How does the processor know the difference between a signed and an unsigned integer?

Convert 10011001 to an unsigned integer.

Convert 10001100 to a signed integer.

Convert 00011100 to a signed integer.

Convert -128 to an eight-bit binary value.

Convert 64 to an eight-bit binary value.

How do we represent -1 with a sixteen-bit binary value?

Briefly explain what is meant by sign extension and why its necessary.