Two’s Complement for signed numbers
Starting value 00000001
Step 1: Reverse the bits 11111110
Step 2: Add 1 to the value from Step 1 11111110 + 00000001
Sum: Two’s-complement representation 11111111 (can be reversed same way)

1. First, the CPU has to fetch the instruction from an area of memory called the instruction
queue. Right after doing this, it increments the instruction pointer.
2. Next, the CPU decodes the instruction by looking at its binary bit pattern. This bit pattern
might reveal that the instruction has operands (input values).
3. If operands are involved, the CPU fetches the operands from registers and memory. Sometimes,
this involves address calculations.
4. Next, the CPU executes the instruction, using any operand values it fetched during the earlier
step. It also updates a few status flags, such as Zero, Carry, and Overflow.
5. Finally, if an output operand was part of the instruction, the CPU stores the result of its execution
in the operand.

EAX – automatically used by MUL and DIV (extended accumulator register)
ECX – CPU uses as a loop counter
ESP – addresses data on the stack (extended stack pointer)
ESI/EDI – high speed memory transfer (extended source/ extended destination)
EBP – High level languages, should not be used as general purpose. (extended frame pointer)

• The Carry flag (CF) is set when the result of an unsigned arithmetic operation is too large to
fit into the destination.
• The Overflow flag (OF) is set when the result of a signed arithmetic operation is too large or
too small to fit into the destination.
• The Sign flag (SF) is set when the result of an arithmetic or logical operation generates a
negative result.
• The Zero flag (ZF) is set when the result of an arithmetic or logical operation generates a
result of zero.
• The Auxiliary Carry flag (AC) is set when an arithmetic operation causes a carry from bit 3
to bit 4 in an 8-bit operand.
• The Parity flag (PF) is set if the least-significant byte in the result contains an even number
of 1 bits. Otherwise, PF is clear. In general, it is used for error checking when there is a possibility
that data might be altered or corrupted.

Bit = 1 bit
Nybble = 4 bits
Byte = 8 bits
WORD = 2 bytes
DWORD = 4 bytes
QWORD = 8 bytes