In optical parallel computation the super fast switching speed is very much expected from the switching devices within the computer architecture. Several approaches were proposed in last few decades around the world where uses of non "liner and photo-refractive material:s were seen massively in the purpose of developing :switching devices. By the proper use of non-linear material logical operations (like NAND. AND, NOT, EX-OR gate) can be performed. These operations are all optical in nature. In this paper such an optical system is proposed which is capable to follow the truth table 0/ a R-S flip-flop. Optical NAND and NOT gate are used here as basic building block. 1NI'R000CI1ONScientific and engineering problems are expected required processing rates greater than the limit of 1 Q9logical operations per second. In the next few decades it is expected that this operational limit can be achieved in practice by using photons as information carrier instead of electron (1-5). The inherent parallelism of optical signal is advantageous for such highspeed computations and other digital logic operations. One of the desirable approach in the development of optical computing system is that aimed at a hybrid structure where the conventional electronic Arithmetic Logical Unit (ALU) is replaced by an optical parallel processor, where binary data '1' is expressed as the presence oflight and '0' is considered as the absence of light. In optical parallel computation a switching device is one of the most important thing which can switch an optical signal '0' to '1' state or from 'I' to '0' state by application of another triggering optical signal (6-8). For this purpose non-linear material can take important role. In this paper an optical system is proposed with the help of nonlinear material that can obey the truth table of a R-S flip-flop. We know that in any digita] computing system the memory cell or flip-flop takes an essential role. In this situation we propose a concept of all-optical flip-flop or memory cell that can store optical data in a computing system. which is run by optics instead of electronics. ELECI'RONIC R-S FLIP·FLOPAn R-S flip-flop can be constructed by using two single input NAND gates N. and Nl and two two-input NAND gatesN J andN 4 • as shown in figure-I. The inputs ofN. and Nlare S and Rinputs respectively. LetS=I, R=O. Then the state of the input of each gate and that of the corresponding output can be obtained logically. We obtain the output Y=l in this case and the output y =0 so that the flip-flop is at set state. Similarly, it can be shown that if S=O andR=1 the flip-flop is driven to the reset state. i.e. Y=Oand Y =1. The input S is called set or preset input where as the input R is called reset or clear input. Now if S and R are given '0' input values the output will hold the values what were achieved in its earlier situation (i.e. Y =0, Y = 1 or y =0. Y =1). where S=R= 1 is forbidden state.

An all-optical system for the addition of binary numbers is proposed in which input binary digits are encoded by appropriate cells in two different planes and output binary digits are expressed as the presence (=1) or the absence (=0) of a light signal. The intensity-based optical XOR and AND logic operations are used here as basic building blocks. Nonlinear materials, appropriate cells (pixels), and other conventional optics are utilized in this system.

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