In reality, the 32-bit address generated by a program is not necessarily the physical address at which an operand is stored as the program executes. There is an additional layer of memory management performed by the operating system and the Intel 80x86 CPU.
A paging mechanism is used to map the program's 32-bit addresses into physical addresses. Paging is useful when a logical address generated by a program exceeds the physical memory actually installed in a computer.
It can also be used to swap parts of a program from disk as needed when the program is too large to fit into physical memory. The paging mechanism will be transparent to us as we program in assembly language.
Suppose you buy a PC with 256 MBytes of RAM. What is the eight-hex-digit address of the "last" byte?
Suppose you discover that RAM addresses 000C0000 to 000C7FFF are reserved for a PC's video adapter. How many bytes of memory is this?