Aim: Implementation of Lexical Analyser for ARITHMETIC EXPRESSIONS usign C programming language 

Programming

#include<stdio.h>

#include<conio.h>

#include<ctype.h>

#include<string.h>

#include<stdlib.h>

int keyword_library(char temp[]);

 

int main()

{

      char ch, temp[40], arithmetic_operator[] = "=+%*/-";

      FILE *file_pointer;

      int count, x = 0;

      file_pointer = fopen("C:\\Users\\tusoni\\Desktop\\demo.txt","r");

      if(file_pointer == NULL)

      {

            printf("The file could not be opened.\n");

            exit(0);

      }

      while((ch = fgetc(file_pointer)) != EOF)

      {

            count = 0;

            while(count <= 5)

            {

                  if(ch == arithmetic_operator[count])

                  {

                        printf("\nOperator:\t%c", ch);

                  }

                  count = count + 1;

            }

            if(isalnum(ch))

            {

                  temp[x++] = ch;

            }

            else if((ch == '\n' || ch == ' ') && (x != 0))

            {

                  temp[x] = '\0';

                  x = 0;

                  if(keyword_library(temp) == 1)

                  {

                        printf("\nKeyword:\t%s", temp);

                  }

                  else

                  {

                        printf("\nIdentifier:\t%s", temp);

                  }

            }

      }

      fclose(file_pointer);

      getch();

      return 0;

}

 

int keyword_library(char temp[])

{

      int count = 0, flag = 0;

      char keywords[32][12] = {"return", "continue", "extern", "static", "long", "signed",

                               "switch", "char", "else", "unsigned", "if", "struct",

                               "union", "goto", "while", "float", "enum", "sizeof", "double", "volatile",

                               "const", "case", "for", "break", "void", "register", "int",

                               "do", "default", "short", "typedef", "auto"};

      while(count <= 31)

      {

            if(strcmp(keywords[count], temp) == 0)

            {

                  flag = 1;

                  break;

            }

            count = count + 1;

      }

      return (flag);

}

 

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OUTPUT