Here is the original code: (From Concepts of Programming Languages 12th Edition)

/* front.c - a lexical analyzer system for simple

arithmetic expressions */

#include

#include

/* Global declarations */

/* Variables */

int charClass;

char lexeme [100];

char nextChar;

int lexLen;

int token;

int nextToken;

FILE *in_fp, *fopen();

/* Function declarations */

void addChar();

void getChar();

void getNonBlank();

int lex();

/* Character classes */

#define LETTER 0

#define DIGIT 1

#define UNKNOWN 99

/* Token codes */

#define INT_LIT 10

#define IDENT 11

#define ASSIGN_OP 20

#define ADD_OP 21

#define SUB_OP 22

#define MULT_OP 23

#define DIV_OP 24

#define LEFT_PAREN 25

#define RIGHT_PAREN 26

/******************************************************/

/* main driver */

main() {

/* Open the input data file and process its contents */

if ((in_fp = fopen("front.in", "r")) == NULL)

printf("ERROR - cannot open front.in ");

else {

getChar();

do {

lex();

} while (nextToken! = EOF);

}

}

/*****************************************************/

/* lookup - a function to lookup operators and parentheses

and return the token */

int lookup(char ch) {

switch (ch) {

case '(':

addChar();

nextToken = LEFT_PAREN;

break;

case ')':

addChar();

nextToken = RIGHT_PAREN;

break;

case '+':

addChar();

nextToken = ADD_OP;

break;

case '-':

addChar();

nextToken = SUB_OP;

break;

case '*':

addChar();

nextToken = MULT_OP;

break;

case '/':

addChar();

nextToken = DIV_OP;

break;

 default:

 addChar();

 nextToken = EOF;

 break;

 }

 return nextToken;

}

/*****************************************************/

/* addChar - a function to add nextChar to lexeme */

void addChar() {

 if (lexLen  
 lexeme[lexLen++] = nextChar;
 
 lexeme[lexLen] = 0;
 
 }
 
 else
 
 printf("Error - lexeme is too long ");
 
}
 
/*****************************************************/
 
/* getChar - a function to get the next character of 
 
 input and determine its character class */
 
 void getChar() {
 
 if ((nextChar = getc(in_fp)) != EOF) {
 
 if (isalpha(nextChar))
 
 charClass = LETTER;
 
 else if (isdigit(nextChar))
 
 charClass = DIGIT;
 
 else charClass = UNKNOWN;
 
 }
 
 else
 
 charClass = EOF;
 
}
 
/*****************************************************/
 
/* getNonBlank - a function to call getChar until it
 
 returns a non-whitespace character */
 
void getNonBlank() {
 
 while (isspace(nextChar))
 
 getChar();
 
}
 
/
 
*****************************************************/
 
/* lex - a simple lexical analyzer for arithmetic 
 
 expressions */
 
int lex() {
 
 lexLen = 0;
 
 getNonBlank();
 
 switch (charClass) {
 
/* Parse identifiers */
 
 case LETTER:
 
 addChar();
 
 getChar();
 
 while (charClass == LETTER || charClass == DIGIT) {
 
 addChar();
 
 getChar();
 
 }
 
 nextToken = IDENT;
 
 break;
 
/* Parse integer literals */
 
 case DIGIT:
 
 addChar();
 
 getChar();
 
 while (charClass == DIGIT) {
 
 addChar();
 
 getChar();
 
 }
 
 nextToken = INT_LIT;
 
 break;
 
/* Parentheses and operators */
 
 case UNKNOWN:
 
 lookup(nextChar);
 
 getChar();
 
 break;
 
/* EOF */
 
 case EOF:
 
 nextToken = EOF;
 
 lexeme[0] = 'E';
 
 lexeme[1] = 'O';
 
 lexeme[2] = 'F';
 
 lexeme[3] = 0;
 
 break;
 
 } /* End of switch */
 
 printf("Next token is: %d, Next lexeme is %s ", 
 
 nextToken, lexeme);
 
 return nextToken;
 
} /* End of function lex */ 
  Q1: Modify the lexical analyzer given in Section 4.2 to recognize the following list of reserved words and return their respective token codes: for (FOR_cODE, 30) if (IF_CODE, 31) else (ELSE_coDE, 32) while (WHILE_CODE, 33) int (INT CODE, 35) float (FLOAT_CODE, 36), Q2: Test your program using the following three expressions: if flag) x= x * 10 else int y = 10 for ( i=0 i100 1=1+1) while ( done) sum = sum + 10 Hints The original code for the analyzer is attached as a separate file. The code is written in C, however you are free to implement it in any language you prefer