11 Questions
What are the three memory segments that program's code, data, and stack are loaded into?
code segment, data segment, and stack segment
What is the purpose of the four segment registers in the 8086 microprocessor?
To keep track of the various program segments
What is the function of the CS register?
It contains the code segment number
What is the purpose of the ES register?
To access a second data segment
Which registers can be used in arithmetic and other operations?
Pointer and Index Registers (SP, BP, SI, and DI)
What is the function of the SP register?
It contains the offset of the top of the stack
What is the relationship between the SP and SS registers?
They combine to form the complete address of the top of the stack
What is the primary function of the BP register?
It contains an assumed offset from the SS register
What is the primary function of the SI register?
It points to memory locations in the data segment addressed by DS
What is the function of the DI register?
It performs the same operation as the SI register, acting as the destination for string movement instructions
What is the function of the IP register?
It contains the offset of the next instruction to be executed within the current code segment
Study Notes
Registers in Microprocessor
- BX: Base Register, stores data and serves as an address register
- CX: Count Register, facilitates program loop instructions, serves as a loop counter, and used in string operations
- DX: Data Register, used in multiplication and division operations, and in IO operations like character output and string output functions
32-bit General Purpose Registers
- EAX: Accumulator, used for mult, div, etc., holds an offset
- EBX: Base Index, holds the offset of a data pointer
- ECX: Count, holds the count for some instructions, REP and LOOP, holds the offset of a data pointer
- EDX: Data, holds a portion of the result for mult, holds the offset of a data pointer
- EBP: Base Pointer, holds the base pointer for memory data transfers
- EDI: Destination Index, holds the base destination pointer for string instructions
- ESI: Source Index, holds the base source pointer for string instructions
Special Purpose Registers
- EIP: Instruction Pointer, points to the next instruction in a code segment
- ESP: Stack Pointer, used by the stack, call, and return instructions
- EFLAGS: stores the state of various conditions in the microprocessor, rightmost 5 flag bits and overflow change after many of the arithmetic and logic instructions execute
Programming Model
- The programming model of the 8086 through Pentium II is considered to be program visible because its registers are used during application programming and are specified by the instruction
Register Sizes
- 8-bit registers: AH, AL, BH, BL, CH, CL, DH, DL
- 16-bit registers: AX, BX, CX, DX, SP, BP, SI, DI, SS, DS, CS, ES, FS, GS, IP, FLAGS
- 32-bit registers: EAX, EBX, ECX, EDX, ESI, EDI, ESP, EBP, EIP, EFLAGS
Registers Classification
- Data registers
- Address registers
- Segment registers
- Offset registers
- Status register
General Purpose Registers
- AX (Accumulator Register), preferred register to use in arithmetic, logic, and data transfer instructions
- BX, CX, DX as data registers and SI, DI, BP as address registers
Segment Registers
- CS, DS, and SS registers contain the code, data, and stack segment numbers respectively
- ES (Extra Segment) register for accessing a second data segment
Pointer and Index Registers
- SP (Stack Pointer), BP (Base Pointer), SI (Source Index), and DI (Destination Index) registers point to memory locations
Control Register
- IP (Instruction Pointer), contains the offset of the next instruction to be executed within the current code segment
This quiz covers the basics of computer organization, specifically the functions of BX, CX, and DX registers in microprocessors.
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