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  1. //Program to add crc check bit
  2.  
  3. #include<stdio.h>
  4. #include<string.h>
  5. #define N strlen(g)
  6.  
  7. char t[28],cs[28],g[]="1101";
  8. int a,e,c;
  9.  
  10. void xor(){
  11.     for(c = 1;c < N; c++)
  12.     cs[c] = (( cs[c] == g[c])?'0':'1');
  13. }
  14.  
  15. void crc(){
  16.     for(e=0;e<N;e++)
  17.         cs[e]=t[e];
  18.     do{
  19.         if(cs[0]=='1')
  20.             xor();
  21.         for(c=0;c<N-1;c++)
  22.             cs[c]=cs[c+1];
  23.         cs[c]=t[e++];
  24.     }while(e<=a+N-1);
  25. }
  26.  
  27. int main()
  28. {
  29.     printf("\nEnter data : ");
  30.     scanf("%s",t);
  31.     printf("\n----------------------------------------");
  32.     printf("\nGeneratng polynomial : %s",g);
  33.     a=strlen(t);
  34.     for(e=a;e<a+N-1;e++)
  35.         t[e]='0';
  36.     printf("\n----------------------------------------");
  37.     printf("\nModified data is : %s",t);
  38.     printf("\n----------------------------------------");
  39.     crc();
  40.     printf("\nChecksum is : %s",cs);
  41.     for(e=a;e<a+N-1;e++)
  42.         t[e]=cs[e-a];
  43.     printf("\n----------------------------------------");
  44.     printf("\nFinal codeword is : %s",t);
  45.     printf("\n----------------------------------------");
  46.     printf("\nTest error detection 0(yes) 1(no)? : ");
  47.     scanf("%d",&e);
  48.     if(e==0)
  49.     {
  50.         do{
  51.             printf("\nEnter the position where error is to be inserted : ");
  52.             scanf("%d",&e);
  53.         }while(e==0 || e>a+N-1);
  54.         t[e-1]=(t[e-1]=='0')?'1':'0';
  55.         printf("\n----------------------------------------");
  56.         printf("\nErroneous data : %s\n",t);
  57.     }
  58.     crc();
  59.     for(e=0;(e<N-1) && (cs[e]!='1');e++);
  60.         if(e<N-1)
  61.             printf("\nError detected\n\n");
  62.         else
  63.             printf("\nNo error detected\n\n");
  64.             printf("\n----------------------------------------\n");
  65.         return 0;
  66. }
  67.  
Success #stdin #stdout 0.02s 1724KB
comments (?)
stdin
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101001
stdout
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Enter data : 
----------------------------------------
Generatng polynomial : 1101
----------------------------------------
Modified data is : 101001000
----------------------------------------
Checksum is : 001
----------------------------------------
Final codeword is : 101001001
----------------------------------------
Test error detection 0(yes) 1(no)? : 
No error detected


----------------------------------------
https://ideone.com/n19sD
language:
C (gcc 8.3)
created:
14 years ago
visibility:
public

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