Segmentation fault in C while using pointers -

i don't know what's happening here:

#include<stdio.h> int main()  {     int i, j, *k, x,array[]={5,3,4,1,8,9,2,7,6,0};     int *ptr=array;      for(j=1;j<10;j++) {         printf("---------iteration %d--------------\n",j);         *k=*(ptr+j);   // segmentation error occurring here @ line         printf("key=%d\n",*k);         i=j-1;          while( i>=0 && *k < *(ptr+i)) {             *(ptr+i+1)=*(ptr+i);             i--;         }          *(ptr+i+1) = *k;         printf("%d\n",*(ptr+i+1));          for( x=0;x<10;x++)             printf("%d,",*(ptr+x));          printf("\n");     }      for( i=0;i<10;i++)         printf("%d,",*ptr++);      printf("\n"); } 

the error occurring right after printf statement in for loop , when remove * both sides works answer wrong.

this insertion sort using pointers in c.

the problem is, said, right after printf():

*k=*(ptr+j) 

i didn't far looking @ right side. left side has problem: pointer not initialized, writing address cause trouble.

the right side has memory access too, but, after inspection looks might okay.