Computer arithmetic logic unit

ALU (arithmetic/logic unit) The part of the central processor of a computer in which simple arithmetic and logical operations are performed electronically. For example, the ALU can add, subtract, multiply, or compare two numbers, or negate a number. 

The heart of a eomputer is the CPfl, which in the case of a microcomputer is a microprocessor chip. A microprocessor is made up of a control unit and an control unit determines the sequence of operations by means of instructions frvmi a program stored in tho computer memory. The control unit receives informaiion from tho input device, fetches instructions and data from the memory, and transmits instructions lo the arithmetic logic unit, output. and memory. 

The arithmetic logic unit, or Al,l,i, of a CPU is made up of a series of registers, or accumulators, in which the intermediate results of binary arithmetic and logic operations are accumulated. The Intel Pentium 4 processor coniains nearly 50 million transistors and is capable of operating al clock speeds greater than 5.5 GHz. The Intel tianium processor contains 22 million transistors (the Itanium 2 processor has410 million transistors I. The fastest computers can execute nearly 1 billion instructions per second. 

Accumulator Usually a part of the arithmetic-logic unit (ALU) of a computer that is used for intermediate storage. 

Computer A functional unit that can perform substantial computations, including numerous arithmetic operations and logical operations without human intervention. 

Computer — A device capable of accepting information, applying prescribed processes to the information, and supplying the results of these processes. It usually consists of input and output devices, storage, arithmetic, and logical units, and a control unit. (Computer Dictionary, Sippl and Sippl)... 

On average, a typical computational process can keep four of the arithmetic functional units plus several memory and I/O units busy concurrently, allowing a single AFP to achieve an average computational rate of about 200 to 250 million 16-bit arithmetic and logical operations per second. 

Figure 2 Model of Eckert-von Neumann computer. The Eckert-von Neumann computer is composed of a memory and a central processing unit (CPU). The memory holds both the program and the data. The CPU executes the program which consists of a sequence of instructions which specify memory addresses, arithmetic-logical operations or branch statements.

The computer s central processing unit (CPU) is the portion of a computer that retrieves and executes instructions. The CPU is essentially the brain of a CAD system. It consists of an arithmetic and logic unit (ALU), a control unit, and various registers. The CPU is often simply referred to as the processor. The ALU performs arithmetic operations, logic operations, and related operations, according to the program instructions. 

The CENTRAL PROCESSING UNIT (CPU) decodes and executes the instructions of a computer program. It has circuits that can perform arithmetic and logical operations, e.g., add two numbers or compare them for equality. 

The central processing unit (CPU) controls the overall operation of the computer. It is made up of electronic registers and logic circuits that execute the simple logical and arithmetic operations of which the computer is capable. When these operations are executed in appropriate sequences, the computer can accomplish complex mathematical or data-processing functions. Moreover, if one provides the appropriate electronic interface, these simple operations can be used to control experimental systems, acquire data, or print results on a teletype printer, line printer, oscilloscope, or other peripheral device. 

The physical components of a computer form the hardware. Hardware includes the disk and hard drives, clocks, memory units, and registers for arithmetic and logical operations. Programs and instructions for the computer, including the tapes and disks for their storage, represent the software. 

Burks, Goldstine, and von Neumann first identified the principal components of the general-purpose computer as the arithmetic, memory, control, and input-output organs, and then proceeded to formulate the structure and essential characteristics of each unit for the IAS machine. Alternatives were considered and the rationale behind the choice selected presented. Adoption of the binary, rather than decimal, number system was justified by its simplicity and speed in elementary arithmetic operations, its applicability to logical instructions, and the inherent binary nature of electronie components. Built-in floating-point hardware was ruled out, for the prototype at least, as a waste of the critical memory resource, and because of the increased complexity of the circuitry consideration was given to software implementation of such a facility. 

XOR logic (Fig. 2 ) received a higher than normal amount of attention, because it is an essential part of semiconductor numeracy. Arithmetic units within computers are composed of XOR and AND gates mnning in parallel. Though... 

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