FrontEnd.c

#include <stdio.h>

#include <ctype.h>

#include <stdlib.h>

#include <string.h>

void small();
void dove(int i);
int p[5] = {0,1,2,3,4},
    c = 1, i, k, l, m, pi;
char sw[5] = {'=','-','+','/','*'},
     j[20], a[5], b[5], ch[2];
void main()
{
  printf("Enter the expression:");
  scanf("%s", j);
  printf("\tThe Intermediate code is:\n");
  small();
}
void dove(int i)
{
  a[0] = b[0] = '\0';
  if (!isdigit(j[i + 2]) && !isdigit(j[i - 2]))
  {
    a[0] = j[i - 1];
    b[0] = j[i + 1];
  }
  if (isdigit(j[i + 2]))
  {
    a[0] = j[i - 1];
    b[0] = 't';
    b[1] = j[i + 2];
  }
  if (isdigit(j[i - 2]))
  {
    b[0] = j[i + 1];
    a[0] = 't';
    a[1] = j[i - 2];
    b[1] = '\0';
  }
  if (isdigit(j[i + 2]) && isdigit(j[i - 2]))
  {
    a[0] = 't';
    b[0] = 't';
    a[1] = j[i - 2];
    b[1] = j[i + 2];
    sprintf(ch, "%d", c);
    j[i + 2] = j[i - 2] = ch[0];
  }
  if (j[i] == '*')
    printf("\tt%d=%s*%s\n", c, a, b);
  if (j[i] == '/')
    printf("\tt%d=%s/%s\n", c, a, b);
  if (j[i] == '+')
    printf("\tt%d=%s+%s\n", c, a, b);
  if (j[i] == '-')
    printf("\tt%d=%s-%s\n", c, a, b);
  if (j[i] == '=')
    printf("\t%c=t%d", j[i - 1], --c);
  sprintf(ch, "%d", c);
  j[i] = ch[0];
  c++;
  small();
}
void small()
{
  pi = 0;
  l = 0;
  for (i = 0; i < strlen(j); i++)
  {
    for (m = 0; m < 5; m++)
      if (j[i] == sw[m])
        if (pi <= p[m])
        {
          pi = p[m];
          l = 1;
          k = i;
        }
  }
  if (l == 1)
    dove(k);
  else
    exit(0);
}

// Sample Input

// a=b+c-d