Enrollment No: 120050131108 Compiler Design (170701)Practical
No: 14Aim: Write a program which generate quadruple table for the
given postfix expression.
Theory:While translating a source program into a functionally
equivalent object code representation, a parser may first generate
an intermediate representation. This makes retargeting of the code
possible and allows some optimizations to be carried out that
wouldotherwisenot be possible. The following are commonly used
intermediate representations: 1. Postfix notation 2. Syntax tree 3.
Three-addresscodePostfix NotationIn postfix notation, the
operatorfollowsthe operand. For example, in the expression (ab) *
(c+d) + (ab), the postfix representation is:
Syntax TreeThe syntax tree is nothing more than a condensed form
of the parse tree. The operator and keyword nodes of the parse tree
(Figure 6.5) are moved to their parent, and a chain of
singleproductionsisreplacedby single link (Figure 6.6).Parse tree
for the string id+id*id.Syntax tree for id+id*id.Three-Address
CodeThree address code is a sequence of statements of the
formx=yopz. Since a statement involves no more than three
references, it is called a "three-address statement," and a
sequence of such statements is referred to as three-address code.
For example, the three-address code for the
expressiona+b*c+dis:
Sometimes a statement might contain less than three references;
but it is still called a three-address statement. The following are
the three-address statements used to represent various programming
language constructs: Used for representing arithmetic
expressions:
Used for representing Boolean expressions:
Used for representing array references and dereferencing
operations:
Used for representing a procedure call:
Records with fields for the operators and operands can be used
to represent three-address statements. It is possible to use a
record structure with four fields: the first holds the operator,
thenexttwo hold the operand1 and operand2, respectively, and the
last one holds the result. This representation of a three-address
statement is called a "quadruple representation".Quadruple
RepresentationUsing quadruple representation, the three-address
statementx=yopzis represented by placingopin the operator field,yin
the operand1 field,zin the operand2 field, andxin the result field.
The statementx=op y, whereopis a unary operator, is represented by
placingopin the operator field,yin the operand1 field, andxin the
result field; the operand2 field is not used. A statement like
paramt1 is represented by placing param in the operator field andt1
in the operand1 field;neitheroperand2 nor the result field are
used. Unconditional and conditional jump statements are represented
by placing the target labels in the result field. For example, a
quadruple representation of the three-address code for the
statementx= (a+b) * -c/dis shown in Table 6.1. Thenumbersin
parentheses represent the pointers to the triple
structure.OperatorOperand1Operand2Result
(1)+abt1
(2)ct2
(3)*t1t2t3
(4)/t3dt4
(5)=t4X
Quadruple Representation ofx= (a+b) *c/d
Program Code:#includevoid main(){ char quar[20][4]; char
str[10]; int i=0,q_i=0,j,temp=65; printf("Enter the string:");
scanf("%s",&str[i]);
while(str[i]!='\0'){if(str[i]=='+'||str[i]=='-'||str[i]=='*'||str[i]=='/')
{ quar[q_i][0]=str[i]; quar[q_i][1]=str[i-2];
quar[q_i][2]=str[i-1]; quar[q_i][3]=temp; str[i-2]=temp; temp++;
q_i++;j=i;i=0;j++; while(str[j]!='\0'){ str[j-2]=str[j]; j++; }
str[j-2]='\0'; } else i++; }for(i=0;i
