LAHF - Load Register AH From Flags

Usage: LAHF

Modifies Flags: None

Copies bits 0-7 of the flags register into AH. This includes flags AF, CF, PF, SF and ZF other bits are undefined.

AH := SF ZF xx AF xx PF xx CF

LAR - Load Access Rights (286+ protected)

Usage: LAR dest,src

Modifies Flags: ZF

The high byte of the of the destination register is overwritten by the value of the access rights byte and the low order byte is zeroed depending on the selection in the source operand. The Zero Flag is set if the load operation is successful.

LDS - Load Pointer Using DS

Usage: LDS dest,src

Modifies Flags: None

Loads 32-bit pointer from memory source to destination register and DS. The offset is placed in the destination register and the segment is placed in DS. To use this instruction the word at the lower memory address must contain the offset and the word at the higher address must contain the segment. This simplifies the loading of far pointers from the stack and the interrupt vector table.

LEA - Load Effective Address

Usage: LEA dest,src

Modifies Flags: None

Transfers offset address of "src" to the destination register.

LEAVE - Restore Stack for Procedure Exit (80188+)

Usage: LEAVE

Modifies Flags: LEAVE

Releases the local variables created by the previous ENTER instruction by restoring SP and BP to their condition before the procedure stack frame was initialized.

LES - Load Pointer Using ES

Usage: LES dest,src

Modifies Flags: None

Loads 32-bit pointer from memory source to destination register and ES. The offset is placed in the destination register and the segment is placed in ES. To use this instruction the word at the lower memory address must contain the offset and the word at the higher address must contain the segment. This simplifies the loading of far pointers from the stack and the interrupt vector table.

LFS - Load Pointer Using FS (386+)

Usage: LFS dest,src

Modifies Flags: None

Loads 32-bit pointer from memory source to destination register and FS. The offset is placed in the destination register and the segment is placed in FS. To use this instruction the word at the lower memory address must contain the offset and the word at the higher address must contain the segment. This simplifies the loading of far pointers from the stack and the interrupt vector table.

LGDT - Load Global Descriptor Table (286+ privileged)

Usage: LGDT src

Modifies Flags: None

Loads a value from an operand into the Global Descriptor Table (GDT) register.

LIDT - Load Interrupt Descriptor Table (286+ privileged)

Usage: LIDT src

Modifies Flags: None

Loads a value from an operand into the Interrupt Descriptor Table (IDT) register.

LGS - Load Pointer Using GS (386+)

Usage: LGS dest,src

Modifies Flags: None

Loads 32-bit pointer from memory source to destination register and GS. The offset is placed in the destination register and the segment is placed in GS. To use this instruction the word at the lower memory address must contain the offset and the word at the higher address must contain the segment. This simplifies the loading of far pointers from the stack and the interrupt vector table.

LLDT - Load Local Descriptor Table (286+ privileged)

Usage: LLDT src

Modifies Flags: None

Loads a value from an operand into the Local Descriptor Table Register (LDTR).

LMSW - Load Machine Status Word (286+ privileged)

Usage: LMSW src

Modifies Flags: None

Loads the Machine Status Word (MSW) from data found at "src"

LOCK - Lock Bus

Usage: LOCK
           LOCK: (386+ prefix)

Modifies Flags: None

This instruction is a prefix that causes the CPU assert bus lock signal during the execution of the next instruction. Used to avoid two processors from updating the same data location. The 286 always asserts lock during an XCHG with memory operands. This should only be used to lock the bus prior to XCHG, MOV, IN and OUT instructions.

LODS - Load String (Byte, Word or Double)

Usage: LODS src
           LODSB
           LODSW
           LODSD (386+)

Modifies Flags: None

Transfers string element addressed by DS:SI (even if an operand is supplied) to the accumulator. SI is incremented based on the size of the operand or based on the instruction used. If the Direction Flag is set SI is decremented, if the Direction Flag is clear SI is incremented. Use with REP prefixes.

LOOP - Decrement CX and Loop if CX Not Zero

Usage: LOOP label

Modifies Flags: None

Decrements CX by 1 and transfers control to "label" if CX is not Zero. The "label" operand must be within -128 or 127 bytes of the instruction following the loop instruction

Usage: LOOPE label
           LOOPZ label

Modifies Flags: None

Decrements CX by 1 (without modifying the flags) and transfers control to "label" if CX != 0 and the Zero Flag is set. The "label" operand must be within -128 or 127 bytes of the instruction following the loop instruction.

LOOPNZ/LOOPNE - Loop While Not Zero / Loop While Not Equal

Usage: LOOPNZ label
           LOOPNE label

Modifies Flags: None

Decrements CX by 1 (without modifying the flags) and transfers control to "label" if CX != 0 and the Zero Flag is clear. The "label" operand must be within -128 or 127 bytes of the instruction following the loop instruction.

LSL - Load Segment Limit (286+ protected)

Usage: LSL dest,src

Modifies Flags: ZF

Loads the segment limit of a selector into the destination register if the selector is valid and visible at the current privilege level. If loading is successful the Zero Flag is set, otherwise it is cleared.

LSS - Load Pointer Using SS (386+)

Usage: LSS dest,src

Modifies Flags: None

Loads 32-bit pointer from memory source to destination register and SS. The offset is placed in the destination register and the segment is placed in SS. To use this instruction the word at the lower memory address must contain the offset and the word at the higher address must contain the segment. This simplifies the loading of far pointers from the stack and the interrupt vector table.

LTR - Load Task Register (286+ privileged)

Usage: LTR src

Modifies Flags: None

Loads the current task register with the value specified in "src".

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