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A computer instruction describes an operation such as add or multiply X, while the operand (or operands, as there can be more than one) specify on which X to operate as well as the value of X. Additionally, in assembly language, an operand is a value (an argument) on which the instruction, named by mnemonic, operates.
In computer science, an instruction set architecture (ISA) is an abstract model that generally defines how software controls the CPU in a computer or a family of computers. [1] A device or program that executes instructions described by that ISA, such as a central processing unit (CPU), is called an implementation of that ISA.
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture.A realization of an ISA is called an implementation.An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost (among other things); because the ISA serves as the interface between software and hardware.
In computer engineering, a register–memory architecture is an instruction set architecture that allows operations to be performed on (or from) memory, as well as registers. [1] If the architecture allows all operands to be in memory or in registers, or in combinations, it is called a "register plus memory" architecture.
For example, the architecture shown to the right employs a register file with two read ports, which allows the values stored in any two registers (or the same register) to be ALU operands. Alternatively, it allows either ALU operand to be sourced from an immediate operand (a constant value which is directly encoded in the machine instruction ...
For read operands, this tag takes the place of the architectural register in the instruction. For every register write, a new tag is pulled from a free tag FIFO, and a new mapping is written into the remap file, so that future instructions reading the architectural register will refer to this new tag.
Modifies stack for entry to procedure for high level language. Takes two operands: the amount of storage to be allocated on the stack and the nesting level of the procedure. INSB/INSW: 6C Input from port to string. May be used with a REP prefix to repeat the instruction CX times. equivalent to:
In addition to the opcode, many instructions specify the data (known as operands) the operation will act upon, although some instructions may have implicit operands or none. [10] Some instruction sets have nearly uniform fields for opcode and operand specifiers, whereas others (e.g., x86 architecture) have a less uniform, variable-length structure.