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IMPLEMENTATION OF N-BIT ADDER AND SUBTRACTOR OF LIBRARY COMPONENTS FOR ARITHMETIC UNIT Vishal Kumar Srivastava*, Subhash Kumar Sharma**, S. N. Shukla*** and Himanshu Pandey**** *Department of Physics & Electronics Dr. R.M.L. Avadh University, Faizabad (India) **Department Of Electronics D.D.U. Gorakhpur University, Gorakhpur (India) ***Department of Physics & Electronics Dr. RML Avadh University, Faizabad (India) ****Department of Mathematics & Statistics D.D.U. Gorakhpur University, Gorakhpur (India) ABSTRACT This paper deals with development of an n-bit ALU using VHDL. Normally the most of the industries, now a days are using either 4-bit ALU or 8-bit ALU, so We have generalized this, thus We need not to worry about the bit size of ALU. It has solved all the problems of 4-bit, 8bit and 16-bit ALU's and so on. Hence, We have utilized VHSIC Hardware Description Language and Xilinx in accomplishing this task of development of an n-bit ALU. An Arithmetic and Logic Unit (ALU) is a combinational circuit that performs logic and arithmetic micro-operations on a pair of n-bit operands. The operations performed by an ALU are controlled by a set of function-select inputs. The ALU is the part of computer that actually performs arithmetic and logical operations on data. All of the other elements of the computer system-control unit registers, memory, I/Os are mainly to bring data into the ALU for it to process and then to take the results back out. Key words: Half adder, Full adder, Ripple adder, n-bit adder, Subtractor, n-bit Subtactor.
INTRODUCTION Addition is the most commonly performed arithmetic operation in digital systems. An adder
combines two arithmetic operands using the addition rules. An adder can perform subtraction as the addition of the minuend and the complemented (negated) subtrahend, but we can also