What is the mean of Real memory addressing mode?
In real mode addressing for x86 cpus, memory is addressed with pairs of a segment and offset. The offset is added to the segment address multiplied by 16 to yield a 20-bit (20 binary digits, in other words, from the number 0 to (2^20)-1=1,048,575) address that points to a specific byte (8-bit number) in memory. Real mode is different than protected mode (which is used by Windows 95+, Linux on x86, etc) in that there is no segment protection, no inherent multitasking support, and it is possible to directly access the BIOS interrupts. Note also that the 20-bit address number prevents more than one (1) megabyte of memory from being addressed at a time.
