The 32-bit index registers, ESI and EDI, and their 16-bit rightmost portions.
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BP can also be combined with DI and SI as base register for special addressing. The address in SS register is combined with the offset in BP to get the location of the parameter. SP in association with the SS register (SS:SP) refers to be current position of data or address within the program stack.īase Pointer (BP) − The 16-bit BP register mainly helps in referencing the parameter variables passed to a subroutine. Stack Pointer (SP) − The 16-bit SP register provides the offset value within the program stack.
#SI STRING SECTION REGISTRATION CODE#
IP in association with the CS register (as CS:IP) gives the complete address of the current instruction in the code segment. Instruction Pointer (IP) − The 16-bit IP register stores the offset address of the next instruction to be executed. There are three categories of pointer registers −
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The pointer registers are 32-bit EIP, ESP, and EBP registers and corresponding 16-bit right portions IP, SP, and BP. It is also used with AX register along with DX for multiply and divide operations involving large values. It is also used in input/output operations. For example, in multiplication operation, one operand is stored in EAX or AX or AL register according to the size of the operand.īX is known as the base register, as it could be used in indexed addressing.ĬX is known as the count register, as the ECX, CX registers store the loop count in iterative operations.ĭX is known as the data register. Some of these data registers have specific use in arithmetical operations.ĪX is the primary accumulator it is used in input/output and most arithmetic instructions. Lower and higher halves of the above-mentioned four 16-bit registers can be used as eight 8-bit data registers: AH, AL, BH, BL, CH, CL, DH, and DL. Lower halves of the 32-bit registers can be used as four 16-bit data registers: AX, BX, CX and DX. These 32-bit registers can be used in three ways −Īs complete 32-bit data registers: EAX, EBX, ECX, EDX. The general registers are further divided into the following groups −įour 32-bit data registers are used for arithmetic, logical, and other operations. The registers are grouped into three categories −
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There are ten 32-bit and six 16-bit processor registers in IA-32 architecture. A limited number of registers are built into the processor chip. The registers store data elements for processing without having to access the memory. To speed up the processor operations, the processor includes some internal memory storage locations, called registers. However, reading data from and storing data into memory slows down the processor, as it involves complicated processes of sending the data request across the control bus and into the memory storage unit and getting the data through the same channel. This data can be stored in memory and accessed from thereon. Processor operations mostly involve processing data.