Bit Stuffing Character stuffing using C

This is a program on Bit stuffing and Character stuffing using C language

This program is used for Networking.
In this program it includes both bit and character Stuffing and Unstuffing.

Here is the program

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#include
#include
#include
main()
{
int ch;
clrscr();
do
{
printf("\n");
printf("\n 1:bit stuffing \n 2:character stuffing \n 3.exit \n Enter u r choice \n");
scanf("%d",&ch);
switch(ch)
{
case 1:bit();
break;
case 2:character();
break;
case 3:exit(0);
}
}
while(ch!=3);
getch();
}
bit()
{
FILE *fp,*fp1;
char ch;
int i;
if((fp=fopen("source.txt","w"))==NULL)
{
printf("\n ERROR IN OPENING THE FILE");
exit(0);
}
printf("\n enter data to send press 'e' to end:\n");
i=0;
while(1)
{
scanf("%c",&ch);
if(ch=='e')
break;
if(ch=='1')
i++;
else
i=0;
putc(ch,fp);
if(i==5)
{
putc('0',fp);
i=0;
}
}
fclose(fp);
i=0;
fp=fopen("source.txt","r");
fp1=fopen("dest.txt","w");
printf("\n DATA AFTER STUFFING \n");
while((ch=getc(fp))!=EOF)
{
putc(ch,stdout);
}
fseek(fp,0L,0);
printf("\n DATA AFTER UNSTUFFING \n");
while((ch=getc(fp))!=EOF)
{
if(ch=='1')
i++;
else
i=0;
if(i==5)
{
putc(ch,stdout);
putc(ch,fp1);
ch=getc(fp);
i=0;
}
else
{
putc(ch,stdout);
putc(ch,fp1);
}
}
fclose(fp);
fclose(fp1);
}
character()
{
FILE *fp,*fp1;
char ch,c[2],k[4],j[9];
long beg,end;
if((fp=fopen("input.txt","w"))==NULL)
{
printf("\n inpur.txt file opening problem.....");
exit(0);
}
printf("\n enter data to send at end put '}':\n \n");
while(1)
{
scanf("%c",&ch);
if(ch=='}')
break;
putc(ch,fp);
}
fclose(fp);
if((fp=fopen("input.txt","r"))==NULL)
{
printf("\n input.txt file opening problem.....");
exit(0);
}
if((fp1=fopen("csource.txt","w"))==NULL)
{
printf("\n csource.txt file opening problem.....");
exit(0);
}
fputs(" DLE STX ",fp1);
printf("\n");
printf("\n DATA AFTER STUFFING \n");
while((ch=getc(fp))!=EOF)
{
if(ch=='D')
{
c[0]=getc(fp);
c[1]=getc(fp);
if(c[0]=='L'&&c[1]=='E')
fputs("DLE",fp1);
putc(ch,fp1);
putc(c[0],fp1);
putc(c[1],fp1);

}
else
putc(ch,fp1);
}
fputs(" DLE ETX ",fp1);
fclose(fp);
fclose(fp1);

if((fp=fopen("csource.txt","r"))==NULL)
{
printf("\n source.txt file opening problem.....");
exit(0);
}
if((fp1=fopen("cdest.txt","w"))==NULL)
{
printf("\n cdest.txt file opening problem.....");
exit(0);
}
beg=ftell(fp);
beg+=9;
fseek(fp,-0L,2);
end=ftell(fp);
end-=9;
fclose(fp);
fp=fopen("csource.txt","r");
while((ch=getc(fp))!=EOF)
putc(ch,stdout);
fclose(fp);
printf("\n");
printf("\n THE DATA AFTER UNSTUFFING \n");
fp=fopen("csource.txt","r");
fgets(j,9,fp);
while(beg

Output