An arithmetic-logic unit (ALU) is the part of a computer processor that carries out arithmetic and logic operations on the operands in computer instruction words. In some processors, the ALU is divided into two units, an arithmetic unit (AU) and a logic unit (LU).
The auxiliary carry flag AF watches for a 4-bit (nibble) carry, while the common carry flag CF watches for a carry-out from the MSB of the operand size. This could be an 8-bit carry if using 8-bit registers e.g. al or ah, a 16-bit carry if using 16-bit registers ax, and 32-bit or 64-bit carry when using the corresponding registers, e.g. eax or rax respectively.
General-purpose registers (GPRs) can store both data and addresses, i.e., they are combined data/address registers and rarely the register file is unified to include floating point as well. Status registers hold truth values often used to determine whether some instruction should or should not be executed.
General purpose registers (GPR) are not used for storing any specific type of information. Instead operands as well as addresses are stored at the time of program execution. However the operand and the address information may not be of the same size. For example, in 8-bit microprocessors, the data is 8 bit whereas the address is 16 bit.
In computing, an instruction register (IR) is the part of a CPU's control unit that holds the instruction currently being executed or decoded. In simple processors each instruction to be executed is loaded into the instruction register which holds it while it is decoded, prepared and ultimately executed, which can take several steps.
In computer processors, the overflow flag (sometime called V flag) is usually a single bit in a system status register used to indicate when an arithmetic overflow has occurred in an operation, indicating that the signed two's-complement result would not fit in the number of bits used for the operation (the ALU width).
A program counter is a register in a computer processor that contains the address (location) of the instruction being executed at the current time. A program counter is a register in a computer processor that contains the address (location) of the instruction being executed at the current time.
PSW (Program Status Word) Register. The PSW register is a bit and byte-addressable register. This register reflects the status of the operation that is carried out in the controller. The PSW register determines bank selection by a RS1 and RS0, as shown below. The physical address of the PSW starts from D0h and the individual bits are accessed with D0h to D7h. PSW Registers. Carry Flag (C): The Address of the Carry flag is D7.
There are 21 Special function registers (SFR) in 8051 micro controller and this includes Register A, Register B, Processor Status Word (PSW), PCON etc etc. There are 21 unique locations for these 21 special function registers and each of these register is of 1 byte size.