Single Pass Macro Processor

/* Macro Processor */

#include<stdio.h>
#include<conio.h>
#include<ctype.h>
#include<string.h>
int m=0,i,j,flag=0;
char c,*s1,*s2,*s3,*s4,str[50]=" ",str1[50]=" ";
char mac[10][10];
void main()
{
FILE *fpm=fopen("macro.txt","r");
FILE *fpi=fopen("minput.txt","r");
FILE *fpo=fopen("moutput.txt","w");
clrscr();
while(!feof(fpm))
{
fgets(str,50,fpm);
s1=strtok(str," ");
s2=strtok(NULL," ");
if(strcmp(s1,"MACRO")==0)
{
strcpy(mac[m],s2);
m++;
}
s1=s2=NULL;
}
fgets(str,50,fpi);
while(!feof(fpi))
{
flag=0;
strcpy(str1,str);
for(i=0;i<m;i++)
{
if(strcmp(str1,mac[i])==0)
{
rewind(fpm);
while(!feof(fpm))
{
fgets(str,50,fpm);
s2=strtok(str," ");
s3=strtok(NULL," ");
if(strcmp(s2,"MACRO")==0&&strcmp(s3,str1)==0)
{
fgets(str,50,fpm);
strncpy(s4,str,4);
s4[4]='\0';
while(strcmp(s4,"MEND")!=0)
{
fprintf(fpo,"%s",str);
printf("\n####%s",str);
fgets(str,50,fpm);
strncpy(s4,str,4);
s4[4]='\0';
}
}
}
flag=1;
break;
}
}
if(flag==0)
{
fprintf(fpo,"%s",str);
printf("%s",str);
}
fgets(str,50,fpi);
}
fclose(fpm);
fclose(fpi);
fclose(fpo);
getch();
}

Input Files : 

Macro.txt

MACRO ADD1
MOV A,B
ADD C
MEND
MACRO SUB1
STORE C
MEND

MInput.txt

MOV B,10
MOV C,20
ADD1
MUL C
SUB1
END

MOutput.txt

MOV B,10
MOV C,20
MOV A,B
ADD C
MUL C
STORE C
END


If any flaws Contact to M.Baran Mahamood