 on infix to postfix expression. As we have seen, there are three types of notations. The first one is infix, second one is postfix and third one is prefix. Now today we will focus on, we will take consider infix expression and we will convert that into postfix expression. In infix expression, we have operand, then two operands are there between that operator is there. In postfix, the two operands followed by the operator. Let us see one by one. The learning outcome of the today's session, we will try convert the infix expression into postfix expression. The contents of today's topics are, we will see first of all what are the different rules for evaluating postfix expression, then conversion of infix expression to postfix expression. Let us see the different rules for evaluating the postfix expression. Means whenever you convert the given infix expression into postfix expression, after converting that postfix expression, whether it is correct or wrong, for that these rules are used. For that what we do, we use the first rule says that find out the leftmost operator in the expression. Then select the two operands which are immediately to the left of the binary operator. If the binary operator is unary, select one operand. If the binary operator is binary, they select the two operands to the left of the binary or unary operator which is found. Perform the indicated operation, replace the result and repeat those steps till completion of that entire expression. Consider this simple example. Say infix expression is A and B. So this can be convert A and B. A and B means what? A and B means this A and B means this is infix expression. What is infix? It is operand one, operator and operand two. In postfix, the two operands, that is operand one, operand two, followed by the operator that is AND. Operand one is A, operand two is B, followed by the operator AND. A, operand B. This is infix. A, B and is a postfix. Let us go to the, here we observe that two operands are scanned initially followed by the operator. Now think and give the answer consider the following expression. If the operator has the same priority, in that case how this will be evaluated? Which operator will be evaluated first? Take a pause in the video and try to give the answer. Suppose the expression is A and B and C. What is the answer? The answer is that in case of equal priorities, now both and are having equal priorities. Most, the leftmost operator, leftmost operator is that this one is a leftmost operator. This is the leftmost operator between A and B. That will be evaluated first. Then the rightmost, then the next operator from the left, that is this AND will be evaluated between B and C. This is the correct answer. Priority of the evaluation of the operators when they have got the same priority. Conversion of infix to postfix expression. Then A or B or C. A or B and C. A or B and C is the first equation. Let us convert that into postfix. As per the priority, B and C will be evaluated first. So B and C will be converted into BC AND. This is what BC AND is equal to say T, intermediate result. Substitute that into this equation number 1. So this becomes A or T1. That is again converted back to postfix that is A, T1 or say this is equation number 3. Substitute T1 in the equation number 1, 3. So it becomes A, BC and R. Let us consider one more example of A or B or C. In this expression, in this expression the first, this will be evaluated first. This will be evaluated second. Convert one. Suppose this is equation number 1. Convert this into postfix. So A or B, A or B will be evaluated. Let us convert this A or B is equal to AB or this is infix and this is postfix. So this is equal to say T1, say equation number 2. Substitute this T2 in the equation number 1. So this equation number substitute T1 in equation number 1. So equation 1 will be A or T1. Let us convert say this is equation number 3. Convert into postfix. So equation number 3 will be A, T1 or A, T1 or say this is equation number 4. Substitute the value of T1 in equation number 4. So equation number 4 will become now A. T1 is as given, T1 is AB or AB or I think here A or T1. This should be T1 or C. So this is equal to T1CR. So this equation number 4 now will become T1, T1 in the thing but AB or CR. This is the required postfix expression. If you consider the second example, infix to postfix here. First of all this bracket will be evaluated first. So bracket is evaluated like this. B or C is equal to say BC or say this is equal to T1. So substitute T1. Substitute this T1 in equation number 1. So A and T1. So this is equal to A, T1 and say this is equation number 2. Substitute T1 in equation number 2. So T1 is nothing but A, BC or AND. So this is a required postfix expression for A and B or C. I hope you understood this. The references used for this are given below. I hope. Thank you.