x86 Registers 16-bit
The Intel 8086 microprocessor has a set of 16-bit registers that are classified into different types based on their functions. Here's an overview of the key registers available on the 8086:
General-purpose Registers:
AX (Accumulator Register): Used for arithmetic, logic, and data transfer operations. It is often used in input/output operations and is split into two 8-bit registers:
AH (high byte)
AL (low byte)
BX (Base Register): Primarily used for addressing and data manipulation. It is also split into two 8-bit registers:
BH (high byte)
BL (low byte)
CX (Count Register): Used as a counter in loops or string operations. It is also split into two 8-bit registers:
CH (high byte)
CL (low byte)
DX (Data Register): Used in input/output operations and as an extension for arithmetic operations. It is also split into two 8-bit registers:
DH (high byte)
DL (low byte)
Index Registers:
SI (Source Index): Used as a pointer in string operations and memory addressing.
DI (Destination Index): Used as a pointer for string operations and memory addressing.
Segment Registers:
CS (Code Segment): Points to the segment where the currently executing code is located.
DS (Data Segment): Points to the segment containing data.
SS (Stack Segment): Points to the segment where the stack is located.
ES (Extra Segment): Primarily used for string operations, and may serve as an additional data segment.
Pointer Registers:
SP (Stack Pointer): Points to the top of the stack. It is decremented when data is pushed onto the stack and incremented when data is popped off.
BP (Base Pointer): Primarily used for referencing data on the stack, especially in functions with local variables and parameters.
Status and Control Registers:
IP (Instruction Pointer): Holds the offset address of the next instruction to be executed within the code segment.
FLAGS Register: A 16-bit register that holds flags indicating the status of the processor. It is split into two parts:
Control flags: Used to control processor operations.
Status flags: Indicate the results of operations (e.g., Zero Flag, Carry Flag, Sign Flag).
Other special-purpose registers:
IDT Register: Used in interrupt handling, though this feature is available in later x86 processors.
These registers, especially the segment and pointer registers, play a crucial role in the addressing and execution flow of the 8086 processor.