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CS8602 COMPILER DESIGN LABLIST OF EXPERIMENTS:1. Develop a lexical analyzer to recognize a few patterns in C. (Ex.identifiers, constants, comments, operators etc.). Create a symbol table,while recognizing identifiers.2. Implement a Lexical Analyzer using Lex Tool3. Implement an Arithmetic Calculator...

Description

CS8602 COMPILER DESIGN LAB

LIST OF EXPERIMENTS: 1. Develop a lexical analyzer to recognize a few patterns in C. (Ex.

identifiers, constants, comments, operators etc.). Create a symbol table, while recognizing identifiers. 2. Implement a Lexical Analyzer using Lex Tool 3. Implement an Arithmetic Calculator using LEX and YACC 4. Implement simple code optimization techniques (Constant folding, Strength

reduction andAlgebraic transformation) 5. Implement back-end of the compiler for which the three address code is given as

input andthe 8086 assembly language code is produced as output 6. Generate three address code for a simple program using LEX and YACC.

PRACTICALS 30 PERIODS

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Develop a lexical analyzer to recognize a few patterns in C. (Ex. identifiers, constants, comments, operators etc.) Ex. No: 1 a Date : AIM: To Create a Lexical Analyzer using C programming and to create lexemes that is grouped into various categories. ALGORITHM: Step 1: Start the program. Step 2: Create some character arrays to store and manipulate the characters. Step 3: Create a file pointer and get the name of the input file to read the input from. Step 4: Open the input file using the read category. Step 5: Copy the content of the file into a string and then copy it to a character array for processing. Step 6: Use a while loop and browse the content of the file till the end. Step 7: Using a if condition, Separate some symbols like ;{}()#,& and print them as Special Characters. Step 8: Using a if condition, print the letters/words following the int, char or float as the Variables. Step 9: Using a if condition, print the words printf, scanf, main, void etc as the keywords. Step 10: Terminate the program. PROGRAM: #include #include int main() { char tot[100][20]; char a[100],temp[100]; int i=0,j; FILE *p; p=fopen("input1.txt","r"); fscanf(p,"%s",a); strcpy(tot[i],a); strcpy(temp,"Null"); printf("\nLexeme\tToken\n\n"); i=1; while(strcmp(a,"END")!=0) { if((strcmp(a,";")==0)||(strcmp(a,"")==0)||(strcmp(a,",")==0)||(strcmp(a,"&")= =0)) { printf ("\n%s\t", a); printf("Special Character\t"); } else if((strcmp(temp,"int")==0)||(strcmp(temp,"float")==0)||(strcmp(temp,"char")==0)) { printf("\n%s\t",a); printf("variable\t"); }

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else if((strcmp(a,"scanf")==0)||(strcmp(a,"printf")==0)||(strcmp(a,"main")==0)||(strcmp(a,"void")==0)) { printf("\n%s\t",a); printf("keywords\t"); } strcpy(temp,a); strcpy(tot[i],a); i++; fscanf(p,"%s",a); } printf("\t%d",i); printf("\n%s",tot[i-1]); } input1.txt # include < stdio.h > void main ( ) { int a = 100 ; } END OUTPUT: [root@sys70 2]# cc ex2.c [root@sys70 2]# ./a.out LexemeToken

# < > void main ( ) { a ; }

Special Character Special Character Special Character keywords keywords Special Character Special Character Special Character variable Special Character Special Character

RESULT: Thus the C program to implement the Lexical Analyzer is done and the required Lexemes are obtained and the output is verified.

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IMPLEMENTATION OF SYMBOL TABLE Ex.No: 1 b Date:

AIM: To write a C program to implement a symbol table.

1. 2. 3. 4. 5. 6. 7.

8.

ALGORITHM Start the Program. Get the input from the user with the terminating symbol ‘$’. Allocate memory for the variable by dynamic memory allocation function. If the next character of the symbol is an operator then only the memory is allocated. While reading , the input symbol is inserted into symbol table along with its memoryaddress. The steps are repeated till”$”is reached. To reach a variable, enter the variable to the searched and symbol table has been checkedfor corresponding variable, the variable along its address is displayed as result. Stop the program.

PROGRAM:( IMPLEMENTATION OF SYMBOL TABLE) #include #include #include #include #include #includeSpecial Characters",yytext);} %% int main() { FILE *fp; fp=fopen("input.txt","r"); yyin=fp; yylex(); return 0; } int yywrap() { return 1; 7

}

input.txt: int main() { int a,b; printf("hello"); float c; char d; return 0; } OUTPUT: [root@sys70 3]# lex ex3.l [root@sys70 3]# cc lex.yy.c [root@sys70 3]# ./a.out int=> Keywords main=>functions (=>Special Characters )=>Special Characters {=>Special Characters int=> Keywords a=>Identifiers ,=>Special Characters b=>Identifiers ;=>Special Characters printf=>functions (=>Special Characters "=>Special Characters hello =>Identifiers "=>Special Characters )=>Special Characters ;=>Special Characters float=> Keywords c=>Identifiers ;=>Special Characters char=> Keywords d=>Identifiers ;=>Special Characters return=> Keywords 0=>Keywords ;=>Special Characters }=>Special Characters

RESULT: Thus the required Lexical Analyzer is designed and the required output is obtained and verified. 8

IMPLEMENT AN ARITHMETIC CALCULATOR USING LEX AND YACC Ex.No: 3 Date : AIM: To create a calculator using Lex and Yacc programs. ALGORITHM: Step 1: Start the program. Step 2: Include the necessary header files. Step 3: Use a function for printing the error message. Step 4: Get the input from the user and parse it. Step 5: Check the input is a valid expression or not. Step 6: Write separate operations for addition, subtraction, multiplication and division using the expr and matching it with the operators in the in the input. Step 7: Print the error messages for the invalid operators. Step 8: Print the output of the expression. Step 9: Terminate the program. PROGRAM: 4d.l %{ #include #include #include "y.tab.h" void yyerror(char*); extern int yylval; %} %% [ \t]+ ; [0-9]+ {yylval = atoi(yytext); return INTEGER;} [-+*/] {return *yytext;} "(" {return *yytext;} ")" {return *yytext;} \n {return *yytext;} . {char msg[25]; sprintf(msg,"%s ","invalid character",yytext); yyerror(msg); } 4d.y %{ #include #include int yylex(void); #include "y.tab.h" %} %token INTEGER %% expr: expr '\n' { printf("%d\n",$1); } 9

| 'n' expr: expr '+' mulex { $$ = $1 + $3; } | expr '-' mulex { $$ = $1 - $3; } | mulex { $$ = $1; } mulex: mulex '*' term { $$ = $1 * $3; } | mulex '/' term { $$ = $1 / $3; } | term { $$ = $1; } term: '(' expr ')' { $$ = $2; } | INTEGER { $$ = $1; } %% void yyerror(char *s) { fprintf(stderr,"%s\n",s); return; } yywrap() { return(1); } int main(void) { /*yydebug=1;*/ yyparse(); return 0; } OUTPUT: [root@sys70 4d]# lex 4d.l [root@sys70 4d]# yacc -d 4d.y [root@sys70 4d]# cc y.tab.c lex.yy.c -ll [root@sys70 4d]# ./a.out 10+20-50 -20 12*10 120 1/1 1 100+100 200 10-10 0

RESULT: Thus a calculator is formed using Yacc and the expressions are checked and the output of the valid expressions are obtained and verified successfully.

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Ex.No: 4

IMPLEMENT SIMPLE CODE OPTIMIZATION TECHNIQUES

Date : AIM: To write a C program to implement Code Optimization Techniques. ALGORITHM: Step 1: Start the program. Step 2: Include the necessary header files. Step 3: Declare necessary character arrays for input and output and also a structure to include it. Step 4: Get the Input: Set of ‘L’ values with corresponding ‘R’ values and Step 4: Implement the principle source of optimization techniques. Step 5: The Output should be of Intermediate code and Optimized code after eliminating common expressions. Step 6: Terminate the program. PROGRAM: #include #include #include struct op { char l; char r[20]; } op[10],pr[10]; void main() { int a,i,k,j,n,z=0,m,q; char *p,*l; char temp,t; char *tem; clrscr(); printf("Enter the Number of Values:"); scanf("%d",&n); for(i=0;i...