One Pass Macro processor program in C

"C" program for the implementation of a one pass macro processor
#include<stdio.h>
#include<conio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
FILE *f1,*f2,*f3,*f4,*f5;
int len,i,pos=1;
char arg[20],mne[20],opnd[20],la[20],name[20],mne1[20],opnd1[20],pos1[10],pos2[10];
clrscr();
f1=fopen("input.txt","r");
f2=fopen("namtab.txt","w+");
f3=fopen("deftab.txt","w+");
f4=fopen("argtab.txt","w+");
f5=fopen("op.txt","w+");
fscanf(f1,"%s%s%s",la,mne,opnd);
while(strcmp(mne,"END")!=0)
{
if(strcmp(mne,"MACRO")==0)
{
fprintf(f2,"%s\n",la);
fseek(f2,SEEK_SET,0);
fprintf(f3,"%s\t%s\n",la,opnd);
fscanf(f1,"%s%s%s",la,mne,opnd);
while(strcmp(mne,"MEND")!=0)
{
if(opnd[0]=='&')
{
itoa(pos,pos1,5);
strcpy(pos2,"?");
strcpy(opnd,strcat(pos2,pos1));
pos=pos+1;
}
fprintf(f3,"%s\t%s\n",mne,opnd);
fscanf(f1,"%s%s%s",la,mne,opnd);
}
fprintf(f3,"%s",mne);
}
else
{
fscanf(f2,"%s",name);
if(strcmp(mne,name)==0)
{
len=strlen(opnd);
for(i=0;i<len;i++)
{
if(opnd[i]!=',')
fprintf(f4,"%c",opnd[i]);
else
fprintf(f4,"\n");
}
fseek(f3,SEEK_SET,0);
fseek(f4,SEEK_SET,0);
fscanf(f3,"%s%s",mne1,opnd1);
fprintf(f5,".\t%s\t%s\n",mne1,opnd);
fscanf(f3,"%s%s",mne1,opnd1);
while(strcmp(mne1,"MEND")!=0)
{
if((opnd[0]=='?'))
{
fscanf(f4,"%s",arg);
fprintf(f5,"-\t%s\t%s\n",mne1,arg);
}
else
fprintf(f5,"-\t%s\t%s\n",mne1,opnd1);
fscanf(f3,"%s%s",mne1,opnd1);
}
}
else
fprintf(f5,"%s\t%s\t%s\n",la,mne,opnd);
}
fscanf(f1,"%s%s%s",la,mne,opnd);
}
fprintf(f5,"%s\t%s\t%s",la,mne,opnd);
fclose(f1);
fclose(f2);
fclose(f3);
fclose(f4);
fclose(f5);
printf("files to be viewed \n");
printf("1. argtab.txt\n");
printf("2. namtab.txt\n");
printf("3. deftab.txt\n");
printf("4. op.txt\n");
getch();
}

    



Input.txt

EX1 MACRO &A,&B
- LDA &A
- STA &B
- MEND -
SAMPLE START 1000
- EX1 N1,N2
N1 RESW 1
N2 RESW 1
- END -

Argtab.txt

N1
N2

Op.txt

SAMPLE START 1000
. EX1 N1,N2
- LDA ?1
- STA ?2
N1 RESW 1
N2 RESW 1
- END -

Deftab.txt

EX1 &A,&B
LDA ?1
STA ?2
MEND


Namtab.txt

EX1