This explanation is based on x86 systems and the relevant registers that process instruction sets for executables. We are not going to discuss in detail all registers for brevity, but we will describe the most important ones for the scope of this chapter. The registers that are specifically highlighted are 32-bits in size and are known as the extended registers.

They are extended because they have 16-bits added to the previous 16-bit registers. For example, the older 16-bit general purpose registers could be identified by simply removing the E from the front of the register name, so EBX also contains the 16-bit BX register. The BX register is actually the combination of two smaller 8-bit registers, the BH and the BL. The H and the L signify the High Byte and the Low Byte register. There are extensive books written on this subject alone and replicating that information would not be directly useful to our purpose. Overall, registers are broken down into two forms...