February 18th, 2024
| 64 bits | 32 bits | 16 bits | 8 bits |
| rax | eax | ax | al |
| rbx | ebx | bx | bl |
| rcx | ecx | cx | cl |
| rdx | edx | dx | dl |
| rsi | esi | si | sil |
| rdi | edi | di | dil |
| rbp | ebp | bp | bpl |
| rsp | esp | sp | spl |
| r8 | r8d | r8w | r8b |
| r9 | r9d | r9w | r9b |
| r10 | r10d | r10w | r10b |
| r11 | r11d | r11w | r11b |
| r12 | r12d | r12w | r12b |
| r13 | r13d | r13w | r13b |
| r14 | r14d | r14w | r14b |
| r15 | r15d | r15w | r15b |
Bit: 0, Label: CF, Description: Carry Flag: Set by arithmetic instructions
which generate either a carry or borrow. Set when an operation generates a
carry to or a borrow from a destination operand.
Bit: 2, Label: PF, Description: Parity flag: Set by most CPU instructions
if the least significant (aka the low-order bits) of the destination operand
contain an even number of 1's.
Bit: 4, Label: AF, Description: Auxiliary Carry Flag: Set if there is a
carry or borrow involving bit 4 of EAX. Set when a CPU instruction generates
a carry to or a borrow from the low-order 4 bits of an operand. This flag is
used for binary coded decimal (BCD) arithmetic.
Bit: 6, Label: ZF, Description: Zero Flag: Set by most instructions if the
result an operation is binary zero.
Bit: 7, Label: SF, Description: Sign Flag: Most operations set this bit the
same as the most significant bit (aka high-order bit) of the result. 0 is
positive, 1 is negative.
Bit: 8, Label: TF, Description: Trap Flag: (sometimes named a Trace Flag.)
Permits single stepping of programs. After executing a single instruction,
the processor generates an internal exception 1. When Trap Flag is set by a
program, the processor generates a single-step interrupt after each
instruction. A debugging program can use this feature to execute a program
one instruction at a time.
Bit: 9, Label: IF, Description: Interrupt Enable Flag: when set, the
processor recognizes external interrupts on the INTR pin. When set,
interrupts are recognized and acted on as they are received. The bit can be
cleared to turn off interrupt processing temporarily.
Bit:10, Label: DF, Description: Direction Flag: Set and cleared using the
STD and CLD instructions. It is used in string processing. When set to 1,
string operations process down from high addresses to low addresses. If
cleared, string operations process up from low addresses to high addresses.
Bit:11, Label: OF, Description: Overflow Flag: Most arithmetic instructions
set this bit, indicating that the result was too large to fit in the
destination. When set, it indicates that the result of an operation is too
large or too small to fit in the destination operand.
Bit:12-13, Label: IOPL , Description: Input/Output privilege level flags:
Used in protected mode to generate four levels of security.
Bit:14, Label: NT, Description: Nested Task Flag: Used in protected mode.
When set, it indicates that one system task has invoked another via a CALL
Instruction, rather than a JMP.
Bit:16, Label: RF, Description: Resume Flag: Used by the debug registers
DR6 and DR7. It enables you to turn off certain exceptions while debugging
code.
Bit:17, Label: VM, Description: Virtual 8086 Mode flag: Permits 80386 to
behave like a high speed 8086.
SF: Sign Flag. Set when the result of an operation forces the operand to
become negative.ZF: Zero Flag. Set when the result of an operation become zero (conditional
jumps).OF: Overflow Flag. Set when the result of an arithmetic operation on a
signed integer is too large to fit.CF: Carry Flag. Used in unsigned arithmetic expressions.IF: Interrupt flag: Usually active when debugging (step through code).