Symbol Table is a data structure that supports an effective and efficient way of storing data about various names occurring in the source code. These names are used in the source code to identify the different program elements, like a variable, constants, procedures, and the labels of statements.The symbol table is searched each time a name is encountered in the source text. When a new name or new data about an existing name is found, the content of the symbol table modifies. Thus, the symbol table should have an effective structure for creating the data held in the table also ... Read More

While generating three address codes for the given expression, it can specify the address of the Label in goto statements. It is very difficult to assign locations of these label statements in one pass so, two passes are used. In the first pass, it can leave these addresses unspecified & in the next pass, and it can fill these addresses. Therefore filling of incomplete transformation is called Backpatching.One-pass code generation using backpatchingBackpatching can be used to generate a program for boolean expressions and the flow of control statements in one pass. In this, synthesized attributes truelist and falselist of non-terminal ... Read More

Control statements are the statements that change the flow of execution of statements.Consider the GrammarS → if E then S1        |if E then S1 else S2         |while E do S1In this grammar, E is the Boolean expression depending upon which S1 or S2 will be executed.Following representation shows the order of execution of an instruction of if-then, ifthen-else, & while do.𝐒 → 𝐢𝐟 𝐄 𝐭𝐡𝐞𝐧 𝐒𝟏E.CODE & S.CODE are a sequence of statements which generate three address code.E.TRUE is the label to which control flow if E is true.E.FALSE is the label to which ... Read More

Control statements are the statements that change the flow of execution of statements. For example, If, If-else, Switch-Case, while-do statements. In programming languages, Boolean expressions are used toAlter the flow of control− Boolean expressions are used as conditional expressions in a statement that alter the flow of control. The value of such Boolean expression is implicit in a position reached in a program. For example, if (E) S, the expression E should be true if statement S is reached.Compute logical values− A Boolean expression can define true or false values. Such Boolean expressions can be computed in parallel to arithmetic ... Read More

Boolean means True or False. It can also be represented by 1 or 0.Boolean Expression is the expression that returns true or false. Boolean Expression can be represented in two ways−Conditional ExpressionsFor example, If a > b{     cout Y)A = B + CSolution(1) If A < B goto(4)(2) If X > Y goto(4)(3) goto(6)(4) T = B + C(5) A = TExample3− Write three address code for a > b 𝐀𝐍𝐃 c < d 𝐀𝐍𝐃 e < f.Solution(1) If a > b goto(4)(2) t1 = 0(3) goto(5)(4) t1 = 1(5) If c < d goto(8)(6) t2 = 0(7) goto(9)(8) t2 = 1(9) If e < f goto(12)(10) t3 = 0(11) goto(13)(12) t3 = 1(13) t4 = t1 𝐀𝐍𝐃 t2(14) t5 = t4 𝐀𝐍𝐃 t3

Assignment statements consist of an expression. It involves only integer variables.Abstract Translation SchemeConsider the grammar, which consists of an assignment statement.S → id = EE → E + EE → E ∗ EE → −EE → (E)E → idHere Translation of E can have two attributes −𝐄. 𝐏𝐋𝐀𝐂𝐄− It tells about the name that will hold the value of the expression.𝐄. 𝐂𝐎𝐃𝐄− It represents a sequence of three address statements evaluating the expression E in grammar represents an Assignment statement. E. CODE represents the three address codes of the statement. CODE for non-terminals on the left is the concatenation of ... Read More

SolutionFirst of all this statement will be converted into Three Address Code as−t1 = a + bt2 = −t1t3 = c + dt4 = t2 ∗ t3t5 = t1 + ct6 = t4 − t5QuadrupleLocationOperatorarg 1arg 2Result(0)+abt1(1)−t1t2(2)+cdt3(3)∗t2t3t4(4)+t1ct5(5)−t4t5t6                                                                                            TripleLocationOperatorarg 1arg 2(0)+ab(1)−(0)(2)+cd(3)∗(1)(2)(4)+(0)c(5)−(3)(4)Array RepresentationQuadruple is a structure that contains atmost four fields, i.e., operator, Argument 1, Argument 2, ... Read More

There are three implementations used for three address code statements which are as follows −QuadruplesTriplesIndirect TriplesQuadruplesQuadruple is a structure that contains atmost four fields, i.e., operator, Argument 1, Argument 2, and Result.OperatorArgument 1Argument 2ResultFor a statement a = b + c, Quadruple Representation places + in the operator field, a in the Argument 1 field, b in Argument 2, and c in Result field.For example− Consider the Statementa = b + c * dFirst, convert this statement into Three Address code∴ Three Address code will bet1 = c ∗ dt2 = b + t1a = t2.After construction of the Three ... Read More

The three-address code is a sequence of statements of the form A−=B op C, where A, B, C are either programmer-defined names, constants, or compiler-generated temporary names, the op represents an operator that can be constant or floatingpoint arithmetic operators or a Boolean valued data or a logical operator. The reason for the name “three address code” is that each statement generally includes three addresses, two for the operands, and one for the result.In the three-address code, atmost three addresses are define any statement. Two addresses for operand & one for the result.Hence, op is an operator.An only a single ... Read More

Parse TreeParse tree is a hierarchical structure that defines the derivation of the grammar to yield input strings. In parsing, the string is derived using the start symbol. The root of the parse tree is that start symbol. It is the graphical description of symbols that can be terminals or non-terminals. Parse tree follows the precedence of operators. The deepest sub-tree traversed first. Therefore, the operator in the parent node has less precedence over the operator in the sub-tree.A Parse Tree for a CFG G = (V, Σ, P, S) is a tree satisfying the following conditions −Root has the ... Read More