Implementation of Lexical Analyser for ARITHMETIC EXPRESSIONS usign C programming language

Aim: Construction of NFA from Regular Expressions using C Progarmming.

Programming

#include<stdio.h>
#include<conio.h>
void main()
{
char reg[20];
int q[20][3],i,j,len,a,b;
clrscr();
for(a=0;a<20;a++)
{
for(b=0;b<3;b++)
{
q[a][b]=0;
}
}
printf("Regular expression: \n");
scanf("%s",reg);
len=strlen(reg);
i=0;
j=1;
while(i<len)
{
if(reg[i]=='a'&&reg[i+1]!='/'&&reg[i+1]!='*')
{
q[j][0]=j+1;
j++;
}
if(reg[i]=='b'&&reg[i+1]!='/'&&reg[i+1]!='*')
{
q[j][1]=j+1;
j++;
}
if(reg[i]=='e'&&reg[i+1]!='/'&&reg[i+1]!='*')
{
q[j][2]=j+1;
j++;
}
if(reg[i]=='a'&&reg[i+1]=='/'&&reg[i+2]=='b')
{
q[j][2]=((j+1)*10)+(j+3);
j++;
q[j][0]=j+1;
j++;
q[j][2]=j+3;
j++;
q[j][1]=j+1;
j++;
q[j][2]=j+1;
j++;
i=i+2;
}
if(reg[i]=='b'&&reg[i+1]=='/'&&reg[i+2]=='a')
{
q[j][2]=((j+1)*10)+(j+3);
j++;
q[j][1]=j+1;
j++;
q[j][2]=j+3;
j++;
q[j][0]=j+1;
j++;
q[j][2]=j+1;
j++;
i=i+2;
}
if(reg[i]=='a'&&reg[i+1]=='*')
{
q[j][2]=((j+1)*10)+(j+3);
j++;
q[j][0]=j+1;
j++;
q[j][2]=((j+1)*10)+(j-1);
j++;
}
if(reg[i]=='b'&&reg[i+1]=='*')
{
q[j][2]=((j+1)*10)+(j+3);
j++;
q[j][1]=j+1;
j++;
q[j][2]=((j+1)*10)+(j-1);
j++;
}
if(reg[i]==')'&&reg[i+1]=='*')
{
q[0][2]=((j+1)*10)+1;
q[j][2]=((j+1)*10)+1;
j++;
}
i++;
}
printf("Transition function \n");
for(i=0;i<=j;i++)
{
if(q[i][0]!=0)
printf("\n q[%d,a]-->%d",i,q[i][0]);
if(q[i][1]!=0)
printf("\n q[%d,b]-->%d",i,q[i][1]);
if(q[i][2]!=0)
{
if(q[i][2]<10)
printf("\n q[%d,e]-->%d",i,q[i][2]);
else
printf("\n q[%d,e]-->%d & %d",i,q[i][2]/10,q[i][2]%10);
}
}
getch();
}

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Implementation of Code Generator using C programming language

Aim: Implementation of Code Generator using C programming language 

Programming

#include"stdio.h"
#include"conio.h"
#include"string.h"
int i=1,j=0,no=0,tmpch=90;
char str[100],left[15],right[15];
void findopr();
void explore();
void fleft(int);
void fright(int);
struct exp
{
int pos;
char op;
}k[15];
void main()
{
clrscr();
printf("\t\tINTERMEDIATE CODE GENERATION\n\n");
printf("Enter the Expression :");
scanf("%s",str);
printf("The intermediate code:\t\tExpression\n");
findopr();
explore();
getch();
}
void findopr()
{
for(i=0;str[i]!='\0';i++)
if(str[i]==':')
{
k[j].pos=i;
k[j++].op=':';
}
for(i=0;str[i]!='\0';i++)
if(str[i]=='/')
{
k[j].pos=i;
k[j++].op='/';
}
for(i=0;str[i]!='\0';i++)
if(str[i]=='*')
{
k[j].pos=i;
k[j++].op='*';
}
for(i=0;str[i]!='\0';i++)
if(str[i]=='+')
{
k[j].pos=i;
k[j++].op='+';
}
for(i=0;str[i]!='\0';i++)
if(str[i]=='-')
{
k[j].pos=i;
k[j++].op='-';
}
}
void explore()
{
i=1;
while(k[i].op!='\0')
{
fleft(k[i].pos);
fright(k[i].pos);
str[k[i].pos]=tmpch--;
printf("\t%c := %s%c%s\t\t",str[k[i].pos],left,k[i].op,right);
for(j=0;j <strlen(str);j++)
if(str[j]!='$')
printf("%c",str[j]);
printf("\n");
i++;
}
fright(-1);
if(no==0)
{
fleft(strlen(str));
printf("\t%s := %s",right,left);
getch();
exit(0);
}
printf("\t%s :=  %c",right,str[k[--i].pos]);
getch();
}
void fleft(int x)
{
int w=0,flag=0;
x--;
while(x!= -1 &&str[x]!= '+' &&str[x]!='*'&&str[x]!='='&&str[x]!='\0'&&str[x]!='-'&&str[x]!='/'&&str[x]!=':')
{
if(str[x]!='$'&& flag==0)
{
left[w++]=str[x];
left[w]='\0';
str[x]='$';
flag=1;
}
x--;
}
}
void fright(int x)
{
int w=0,flag=0;
x++;
while(x!= -1 && str[x]!= '+'&&str[x]!='*'&&str[x]!='\0'&&str[x]!='='&&str[x]!=':'&&str[x]!='-'&&str[x]!='/')
{
if(str[x]!='$'&& flag==0)
{
right[w++]=str[x];
right[w]='\0';
str[x]='$';
flag=1;
}
x++;
}
}

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OUTPUT