// CRC CODE //
#include<stdio.h>
#include<conio.h>
int
dg=16,dm,dt,data[50],gen[17]={1,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,1}; int
si[16],so[16],tx;
void main() {
void
crc(int msg[]);
int
i,j,k;
printf(“\n
Enter your choice (1/2)\n”); printf(“1 for CRC-CCITT \n”);
printf(“2
for generalised generator polynomial\n”);
printf(“\n
Choice:”);
if(getchar()==’2′)
{
printf(“\n
Enter the degree of generator polynomial\n”);
scanf(“%d”,&dg);
printf(“\n
Enter the generator polynomial\n”);
for(i=dg;i>=0;i–)
scanf(“%d”,&gen[i]);
}
printf(“\n
The generator polynomial is \n”); for(i=dg;i>=0;i–) printf(“%d”,gen[i]);
printf(“\n
Enter the degree of message\n”); scanf(“%d”,&dm);
printf(“\n
Enter the message\n”);
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for(i=dm;i>=0;i–)
dt=dm+dg; |
scanf(“%d”,&data[i]); |
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for(i=0;i<=dm;i++) |
data[dt-i]=data[dm-i]; |
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for(i=1;i<=dg;i++) |
data[dg-i]=0; |
tx=1;
crc(data);
printf(“\n
Enter the received message\n”);
for(i=dt;i>=0;i–)
scanf(“%d”,&data[i]);
tx=0;
crc(data);
}
void crc(int
msg[]) {
int i,j,k,flag;
for(i=0;i<dg;i++) { so[i]=0; si[i]=0;
}
for(i=dt;i>=0;i–) {
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if(gen[0]==1) si[0]=so[dg-1]^msg[i]; |
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else |
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for(j=1;j<=dg-1;j++) |
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if(gen[j]==1) si[j]=so[dg-1]^so[j-1]; |
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else si[j]=so[j-1]; |
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printf(“\n”); |
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for(k=dg-1;k>=0;k–) { |
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so[k]=si[k]; |
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printf(“%d”,so[k]); |
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} |
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} |
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if(tx) |
{ |
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printf(“\n |
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for(k=dg-1;k>=0;k–) { |
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printf(“%d”,so[k]); |
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msg[k]=so[k]; |
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} |
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printf(“\n |
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for(i=dt;i>=0;i–) |
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} |
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if(!tx) |
{ |
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flag=0; |
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for(i=0;i<=dg-1;i++) |
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if(so[i]==1) { |
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flag=1; |
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break; |
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} |
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if(flag==0) printf(“\nResult: |
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else printf(“\n Result: Error in the |
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} |
} |
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SHORTEST PATH
#include<stdio.h>
#include<stdlib.h>
#define nodes 4
#define infinity 100 int n;
int
dist[nodes][nodes]=
{0,100,10,2,
100,0,3,4,
10,3,0,100,
2,4,100,0}; void main(){
int i,s,j,t; void shrt();
printf(“\n Enter the no of
nodes”);
scanf(“%d”,&n);
printf(“\n enter the source & dest
nodes”);
scanf(“%d%d”,&s,&t);
if(s==t){
printf(“\n Source is same as the
destination \t Hence the Distance is 0”); exit(0);
}
shrt(s,t);
}
void shrt(int
s,int t){ struct state { int predecessor; int length; enum{per,tent}label;
}state[nodes];
int i,k,min; struct state *p;
for(p=&state[0];p<&state[n];p++){
p->predecessor=-1; p->length=infinity; p->label=tent;
}
state[t].length=0;state[t].label=per; k=t;
do { for(i=0;i<n;i++) if(dist[k][i]!=0 &&
state[i].label==tent) {
if(state[k].length+dist[k][i]<state[i].length) { state[i].predecessor=k;
state[i].length=state[k].length+dist[k][i];
}
} k=0; min=infinity; for(i=0;i<n;i++)
if(state[i].label==tent &&
state[i].length<min) {
min=state[i].length;
k=i;
}
state[k].label=per;
}while(k!=s);
k=s;
do {
printf(“%d”,k); if (k!=t)
printf(“—>”);
k=state[k].predecessor;
}while(k>=0);
printf(“\n The total distance is
%d”,state[s].length);
}
Example #2
#include<stdio.h>
#include<stdlib.h>
#define nodes 8
#define infinity 100 int n;
int
dist[nodes][nodes]= {0,2,100,1,100,100,100,100,
2,0,2,100,9,100,100,100,
100,2,0,7,100,2,100,100,
1,100,7,0,100,100,7,100,
100,9,100,100,0,4,100,6,
100,100,2,100,4,0,2,100,
100,100,100,7,100,2,0,2,
100,100,100,100,6,100,2,0};
Bit stuffing
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int main()
{
int i,j=0,count=0,temp=0,beg_msg=0,end_msg=0; char
msg[100],smsg[100],bsmsg[100],rmsg[100],omsg[100];
printf(“\n Enter the
message:\n”);
scanf(“%s”,msg);
for(i=0,j=0;msg[i]!=’\0′;i++,j++){
smsg[j]=msg[i];
if(msg[i]==’1′)
/* count the no of successive ones */ count++;
else
count=0;
if(count==5){ /*
stuff a zero after 5 ones */ j++; smsg[j]=’0′; count=0;
}
}
smsg[j]=’\0′;
printf(“\n The stuffed message :\n %s”,smsg);
strcpy(bsmsg,”01111110″); /* add header bits */ strcat(bsmsg,smsg); strcat(bsmsg,”01111110″); /* add the tailor bits*/ printf(“\n The frame to be transmitted
:\n %s”,bsmsg);
/* destuffing */
printf(“\n Enter the received message
:\n”);
scanf(“%s”,rmsg);
temp=0; i=j=0;
for(i=0;rmsg[i+7]!=’\0′;i++){
if(rmsg[i]==’0′ &&
rmsg[i+7]==’0′){ /* check for header & tailor*/ for(j=1;j<7;j++){
if(rmsg[i+j]==’1′)
temp++;
else
{ temp=0;
break;
}
}
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if(temp==6){ |
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/* if 01111110 bit stream found */ |
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if(beg_msg==0) beg_msg=i+8; else{ |
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/* for the first time,msg begins */ |
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end_msg=i; break; } } } else temp=0; }
if((beg_msg==0)||(end_msg==0)){ printf(“\n exit(0); } count=0;
for(i=beg_msg,j=0;i<end_msg;i++,j++){ omsg[j]=rmsg[i]; if(rmsg[i]==’1′) |
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/* for the second time msg ends */ |
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else |
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/* check for consecutive ones */ |
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count=0; if(count==5){ |
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/* if |
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count=0; } } omsg[j]=’\0′; |
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/* ignore it */ |
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} |
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Character Stuffing Program
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
int
i,j=0,hfound=0,tfound=0,error=0;
char
msg[100],smsg[100],tmsg[100],rmsg[100],dmsg[100];
printf(“\nEnter
the message:\n”);
scanf(“%s”,msg);
*(smsg)=’\0′;
*(dmsg)=’\0′;
for(i=0,j=0;msg[i]!=’\0′;i++,j++){
if(!strncmp(msg+i,”DLE”,3))
{
smsg[j]=’\0′; strcat(smsg,”DLEDLE”); i+=2; j+=5;
}
else smsg[j]=msg[i];
}
smsg[j]=’\0′;
strcpy(tmsg,”DLESTX”);
strcat(tmsg,smsg);
strcat(tmsg,”DLEETX”);
printf(“\nThe stuffed message is :\n%s”,tmsg);
/* Destuffing
*/
printf(“\nEnter the received message :\n”); scanf(“%s”,rmsg);
for(i=0,j=0;rmsg[i]!=’\0′;i++)
{
if(!strncmp(rmsg+i,”DLE”,3))
{
i+=3;
if(!strncmp(rmsg+i,”STX”,3))
{
if(!hfound) hfound=1; else error=1;
i+=2; continue;
}
else
if(!strncmp(rmsg+i,”ETX”,3))
{ tfound=1; break;
}
else
if(!strncmp(rmsg+i,”DLE”,3));
else error=1;
}
if(hfound==1)
{
dmsg[j]=rmsg[i]; dmsg[j+1]=’\0′; j++;
}
}
dmsg[j]=’\0′;
if(error||!hfound||!tfound)
{
printf(“\nFraming Error\n
“);
exit(0);
}
printf(“\nThe destuffed message is :\n%s”,dmsg);
}
Encryption by Transposition algorithm
#include<stdio.h>
#include<string.h>
#include<conio.h> #include<stdlib.h>
void main()
{
char
txt[50],kw[10],kw1[10],temp,txt1[10][10],encr[10][10],decr[10][10]; int
lenm,lenk,order[10],i,j,k,temp1,c=0,r,b,count;
printf(“\nEnter the message to be
enrypted: “); scanf(“%s”,txt);
lenm=strlen(txt);
printf(“\nEnter the keyword:
“); scanf(“%s”,kw);
lenk=strlen(kw);
strcpy(kw1,kw);
for(i=0;i<lenk;i++)
order[i]=i;
//sort the keyword
for(i=0;i<lenk;i++)
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for(j=0;j<lenk;j++) if(kw1[j]>kw1[i]) { |
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temp=kw1[j]; |
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kw1[j]=kw1[i]; |
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kw1[i]=temp; |
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temp1=order[j]; |
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order[j]=order[i]; |
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} } |
order[i]=temp1; |
printf(“\n Order of letters after
sorting: “); for(i=0;i<lenk;i++)
printf(“%d
“,order[i]);
r=lenm/lenk; //no.
of rows
b=lenm%lenk;
if(b!=0) r++;
//convert message to matrix
count=0; for(i=0;i<r;i++) {
for(j=0;j<lenk &&
count<=lenm;j++) txt1[i][j]=txt[count++]; if(count>lenm) { while(b!=lenk) {
txt1[i][b]=’a’+c++;
b++;
}
}
}
//encryption
printf(“\nThe encrypted message
:\n”);
for(k=0;k<lenk;k++) { for(i=0;i<r;i++) { j=order[k]; encr[i][k]=txt1[i][j]; printf(“%c”,encr[i][k]);
}
}
//at the receiver printf(“\nEnter
the keyword: “); scanf(“%s”,kw1);
if(strcmp(kw,kw1)) {
printf(“Wrong Key!!”);
exit(0);
}
//decryption
for(i=0;i<lenk;i++) { j=order[i]; for(k=0;k<r;k++)
decr[k][j]=encr[k][i];
}
printf(“\n The original message
is: “);
for(i=0;i<r;i++) for(j=0;j<lenk;j++) { if(((i*lenk)+j)==lenm){ break; }
printf(“%c”,decr[i][j]);
}
}
Encryption by Substitution algorithm
#include<stdio.h> #include<string.h> void
main()
{
char
msg[100],encr[100],decr[100],rec[100];
int i;
printf(“\n
Enter the message for encryption:\n “);
scanf(“%s”,msg);
for(i=0;*(msg+i)!=’\0′;i++) {
if((*(msg+i)>=’a’
&& *(msg+i)<=’w’)||(*(msg+i)>=’A’ && *(msg+i)<=’W’))
*(encr+i)=*(msg+i)+3;
else
if((*(msg+i)>=’x’
&& *(msg+i)<=’z’)||(*(msg+i)>=’X’ && *(msg+i)<=’Z’))
*(encr+i)=*(msg+i)+3-26;
else
*(encr+i)=*(msg+i)+3;
}
*(encr+i)=’\0′;
printf(“\n Encrypted message: %s\n”,encr);
/* Decryption
*/
printf(“\n
Enter the message for decryption:\n “);
scanf(“%s”,rec);
for(i=0;*(rec+i)!=’\0′;i++) {
if((*(rec+i)>=’d’ &&
*(rec+i)<=’z’)||(*(rec+i)>=’D’ && *(rec+i)<=’Z’))
*(decr+i)=*(rec+i)-3;
else
if((*(rec+i)>=’a’ && *(rec+i)<=’c’)||(*(rec+i)>=’A’
&& *(rec+i)<=’C’))
*(decr+i)=*(rec+i)-3+26; else
*(decr+i)=*(rec+i)-3;
}
*(decr+i)=’\0′;
printf(“\n The decrypted message:\n %s”,decr);
}
// CRC CODE //
#include<stdio.h>
#include<conio.h>
int
dg=16,dm,dt,data[50],gen[17]={1,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,1}; int
si[16],so[16],tx;
void main() {
void
crc(int msg[]);
int
i,j,k;
printf(“\n
Enter your choice (1/2)\n”); printf(“1 for CRC-CCITT \n”);
printf(“2
for generalised generator polynomial\n”);
printf(“\n
Choice:”);
if(getchar()==’2′)
{
printf(“\n
Enter the degree of generator polynomial\n”);
scanf(“%d”,&dg);
printf(“\n
Enter the generator polynomial\n”);
for(i=dg;i>=0;i–)
scanf(“%d”,&gen[i]);
}
printf(“\n
The generator polynomial is \n”); for(i=dg;i>=0;i–) printf(“%d”,gen[i]);
printf(“\n
Enter the degree of message\n”); scanf(“%d”,&dm);
printf(“\n
Enter the message\n”);
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for(i=dm;i>=0;i–)
dt=dm+dg; |
scanf(“%d”,&data[i]); |
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for(i=0;i<=dm;i++) |
data[dt-i]=data[dm-i]; |
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for(i=1;i<=dg;i++) |
data[dg-i]=0; |
tx=1;
crc(data);
printf(“\n
Enter the received message\n”);
for(i=dt;i>=0;i–)
scanf(“%d”,&data[i]);
tx=0;
crc(data);
}
void crc(int
msg[]) {
int i,j,k,flag;
for(i=0;i<dg;i++) { so[i]=0; si[i]=0;
}
for(i=dt;i>=0;i–) {
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if(gen[0]==1) si[0]=so[dg-1]^msg[i]; |
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else |
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for(j=1;j<=dg-1;j++) |
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if(gen[j]==1) si[j]=so[dg-1]^so[j-1]; |
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else si[j]=so[j-1]; |
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printf(“\n”); |
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for(k=dg-1;k>=0;k–) { |
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so[k]=si[k]; |
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printf(“%d”,so[k]); |
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} |
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} |
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if(tx) |
{ |
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printf(“\n |
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for(k=dg-1;k>=0;k–) { |
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printf(“%d”,so[k]); |
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msg[k]=so[k]; |
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} |
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printf(“\n |
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for(i=dt;i>=0;i–) |
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} |
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if(!tx) |
{ |
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flag=0; |
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for(i=0;i<=dg-1;i++) |
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if(so[i]==1) { |
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flag=1; |
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break; |
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} |
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if(flag==0) printf(“\nResult: |
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else printf(“\n Result: Error in the |
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} |
} |
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SHORTEST PATH
#include<stdio.h>
#include<stdlib.h>
#define nodes 4
#define infinity 100 int n;
int
dist[nodes][nodes]=
{0,100,10,2,
100,0,3,4,
10,3,0,100,
2,4,100,0}; void main(){
int i,s,j,t; void shrt();
printf(“\n Enter the no of
nodes”);
scanf(“%d”,&n);
printf(“\n enter the source & dest
nodes”);
scanf(“%d%d”,&s,&t);
if(s==t){
printf(“\n Source is same as the
destination \t Hence the Distance is 0”); exit(0);
}
shrt(s,t);
}
void shrt(int
s,int t){ struct state { int predecessor; int length; enum{per,tent}label;
}state[nodes];
int i,k,min; struct state *p;
for(p=&state[0];p<&state[n];p++){
p->predecessor=-1; p->length=infinity; p->label=tent;
}
state[t].length=0;state[t].label=per; k=t;
do { for(i=0;i<n;i++) if(dist[k][i]!=0 &&
state[i].label==tent) {
if(state[k].length+dist[k][i]<state[i].length) { state[i].predecessor=k;
state[i].length=state[k].length+dist[k][i];
}
} k=0; min=infinity; for(i=0;i<n;i++)
if(state[i].label==tent &&
state[i].length<min) {
min=state[i].length;
k=i;
}
state[k].label=per;
}while(k!=s);
k=s;
do {
printf(“%d”,k); if (k!=t)
printf(“—>”);
k=state[k].predecessor;
}while(k>=0);
printf(“\n The total distance is
%d”,state[s].length);
}
Example #2
#include<stdio.h>
#include<stdlib.h>
#define nodes 8
#define infinity 100 int n;
int
dist[nodes][nodes]= {0,2,100,1,100,100,100,100,
2,0,2,100,9,100,100,100,
100,2,0,7,100,2,100,100,
1,100,7,0,100,100,7,100,
100,9,100,100,0,4,100,6,
100,100,2,100,4,0,2,100,
100,100,100,7,100,2,0,2,
100,100,100,100,6,100,2,0};
Bit stuffing
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
int main()
{
int i,j=0,count=0,temp=0,beg_msg=0,end_msg=0; char
msg[100],smsg[100],bsmsg[100],rmsg[100],omsg[100];
printf(“\n Enter the
message:\n”);
scanf(“%s”,msg);
for(i=0,j=0;msg[i]!=’\0′;i++,j++){
smsg[j]=msg[i];
if(msg[i]==’1′)
/* count the no of successive ones */ count++;
else
count=0;
if(count==5){ /*
stuff a zero after 5 ones */ j++; smsg[j]=’0′; count=0;
}
}
smsg[j]=’\0′;
printf(“\n The stuffed message :\n %s”,smsg);
strcpy(bsmsg,”01111110″); /* add header bits */ strcat(bsmsg,smsg); strcat(bsmsg,”01111110″); /* add the tailor bits*/ printf(“\n The frame to be transmitted
:\n %s”,bsmsg);
/* destuffing */
printf(“\n Enter the received message
:\n”);
scanf(“%s”,rmsg);
temp=0; i=j=0;
for(i=0;rmsg[i+7]!=’\0′;i++){
if(rmsg[i]==’0′ &&
rmsg[i+7]==’0′){ /* check for header & tailor*/ for(j=1;j<7;j++){
if(rmsg[i+j]==’1′)
temp++;
else
{ temp=0;
break;
}
}
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if(temp==6){ |
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/* if 01111110 bit stream found */ |
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if(beg_msg==0) beg_msg=i+8; else{ |
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/* for the first time,msg begins */ |
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end_msg=i; break; } } } else temp=0; }
if((beg_msg==0)||(end_msg==0)){ printf(“\n exit(0); } count=0;
for(i=beg_msg,j=0;i<end_msg;i++,j++){ omsg[j]=rmsg[i]; if(rmsg[i]==’1′) |
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/* for the second time msg ends */ |
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else |
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/* check for consecutive ones */ |
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count=0; if(count==5){ |
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/* if |
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count=0; } } omsg[j]=’\0′; |
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/* ignore it */ |
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} |
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Character Stuffing Program
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void main()
{
int
i,j=0,hfound=0,tfound=0,error=0;
char
msg[100],smsg[100],tmsg[100],rmsg[100],dmsg[100];
printf(“\nEnter
the message:\n”);
scanf(“%s”,msg);
*(smsg)=’\0′;
*(dmsg)=’\0′;
for(i=0,j=0;msg[i]!=’\0′;i++,j++){
if(!strncmp(msg+i,”DLE”,3))
{
smsg[j]=’\0′; strcat(smsg,”DLEDLE”); i+=2; j+=5;
}
else smsg[j]=msg[i];
}
smsg[j]=’\0′;
strcpy(tmsg,”DLESTX”);
strcat(tmsg,smsg);
strcat(tmsg,”DLEETX”);
printf(“\nThe stuffed message is :\n%s”,tmsg);
/* Destuffing
*/
printf(“\nEnter the received message :\n”); scanf(“%s”,rmsg);
for(i=0,j=0;rmsg[i]!=’\0′;i++)
{
if(!strncmp(rmsg+i,”DLE”,3))
{
i+=3;
if(!strncmp(rmsg+i,”STX”,3))
{
if(!hfound) hfound=1; else error=1;
i+=2; continue;
}
else
if(!strncmp(rmsg+i,”ETX”,3))
{ tfound=1; break;
}
else
if(!strncmp(rmsg+i,”DLE”,3));
else error=1;
}
if(hfound==1)
{
dmsg[j]=rmsg[i]; dmsg[j+1]=’\0′; j++;
}
}
dmsg[j]=’\0′;
if(error||!hfound||!tfound)
{
printf(“\nFraming Error\n
“);
exit(0);
}
printf(“\nThe destuffed message is :\n%s”,dmsg);
}
Encryption by Transposition algorithm
#include<stdio.h>
#include<string.h>
#include<conio.h> #include<stdlib.h>
void main()
{
char
txt[50],kw[10],kw1[10],temp,txt1[10][10],encr[10][10],decr[10][10]; int
lenm,lenk,order[10],i,j,k,temp1,c=0,r,b,count;
printf(“\nEnter the message to be
enrypted: “); scanf(“%s”,txt);
lenm=strlen(txt);
printf(“\nEnter the keyword:
“); scanf(“%s”,kw);
lenk=strlen(kw);
strcpy(kw1,kw);
for(i=0;i<lenk;i++)
order[i]=i;
//sort the keyword
for(i=0;i<lenk;i++)
|
for(j=0;j<lenk;j++) if(kw1[j]>kw1[i]) { |
|
|
|
temp=kw1[j]; |
|
|
kw1[j]=kw1[i]; |
|
|
kw1[i]=temp; |
|
|
temp1=order[j]; |
|
|
order[j]=order[i]; |
|
} } |
order[i]=temp1; |
printf(“\n Order of letters after
sorting: “); for(i=0;i<lenk;i++)
printf(“%d
“,order[i]);
r=lenm/lenk; //no.
of rows
b=lenm%lenk;
if(b!=0) r++;
//convert message to matrix
count=0; for(i=0;i<r;i++) {
for(j=0;j<lenk &&
count<=lenm;j++) txt1[i][j]=txt[count++]; if(count>lenm) { while(b!=lenk) {
txt1[i][b]=’a’+c++;
b++;
}
}
}
//encryption
printf(“\nThe encrypted message
:\n”);
for(k=0;k<lenk;k++) { for(i=0;i<r;i++) { j=order[k]; encr[i][k]=txt1[i][j]; printf(“%c”,encr[i][k]);
}
}
//at the receiver printf(“\nEnter
the keyword: “); scanf(“%s”,kw1);
if(strcmp(kw,kw1)) {
printf(“Wrong Key!!”);
exit(0);
}
//decryption
for(i=0;i<lenk;i++) { j=order[i]; for(k=0;k<r;k++)
decr[k][j]=encr[k][i];
}
printf(“\n The original message
is: “);
for(i=0;i<r;i++) for(j=0;j<lenk;j++) { if(((i*lenk)+j)==lenm){ break; }
printf(“%c”,decr[i][j]);
}
}
Encryption by Substitution algorithm
#include<stdio.h> #include<string.h> void
main()
{
char
msg[100],encr[100],decr[100],rec[100];
int i;
printf(“\n
Enter the message for encryption:\n “);
scanf(“%s”,msg);
for(i=0;*(msg+i)!=’\0′;i++) {
if((*(msg+i)>=’a’
&& *(msg+i)<=’w’)||(*(msg+i)>=’A’ && *(msg+i)<=’W’))
*(encr+i)=*(msg+i)+3;
else
if((*(msg+i)>=’x’
&& *(msg+i)<=’z’)||(*(msg+i)>=’X’ && *(msg+i)<=’Z’))
*(encr+i)=*(msg+i)+3-26;
else
*(encr+i)=*(msg+i)+3;
}
*(encr+i)=’\0′;
printf(“\n Encrypted message: %s\n”,encr);
/* Decryption
*/
printf(“\n
Enter the message for decryption:\n “);
scanf(“%s”,rec);
for(i=0;*(rec+i)!=’\0′;i++) {
if((*(rec+i)>=’d’ &&
*(rec+i)<=’z’)||(*(rec+i)>=’D’ && *(rec+i)<=’Z’))
*(decr+i)=*(rec+i)-3;
else
if((*(rec+i)>=’a’ && *(rec+i)<=’c’)||(*(rec+i)>=’A’
&& *(rec+i)<=’C’))
*(decr+i)=*(rec+i)-3+26; else
*(decr+i)=*(rec+i)-3;
}
*(decr+i)=’\0′;
printf(“\n The decrypted message:\n %s”,decr);
}
