2. CPU Registers

As mentioned previously, the CPU contains special storage called registers. The CPU can access data in registers much faster than data in memory, because of which the values fetched from the memory are temporarily stored in these registers to perform operations.

2.1 General-Purpose Registers

The x86 CPU has eight general purpose registers: eax, ebx, ecx, edx, esp, ebp, esi, and edi. These registers are 32 bits (4 bytes) in size. A program can access registers as 32-bit (4 bytes), 16-bit (2 bytes), or 8-bit (1 byte) values. The lower 16 bits (2 bytes) of each of these registers can be accessed as ax, bx, cx, dx, sp, bp, si, and di. The lower 8 bits (1 byte) of eax, ebx, ecx, and edx can be referenced as al, bl, cl, and dl. The higher set of 8 bits can be accessed as ah, bh, ch, and dh. In the following diagram, the eax register contains the 4-byte value 0xC6A93174. A program can access the lower 2 bytes (0x3174) by accessing the ax register, and it can access the lower byte...