Help with this program

//This is the program but printing str1[j] always gives strange output.
//Instead of printing the 15 characters in a sliding pattern in the first instance it concatenates all 5 strings in the first output, 4 in the second and so on.
My objective is to take a string and copy first 10 characters in one string, then next 10 in the next and so on.
If there are any error in the code please correct it.
Thanks in advance
Sucheta

#include<stdio.h>
#include<string.h>

main()
{
char str[20],str1[5][15];
int i,j,k;
scanf("%s",str);
for(i=5,j=0;i>0;i--,j++)
strncpy(str1[j],(str+5-i),15);

for(j=0;j<5;j++)
printf("%s\n",str1[j]);
}

First some errors
str[20] not big enough

strncpy(str1[j],(str+5-i),15);
the second param is the source string (str+5-i) == what???
you say you want 10 char so why copy 15?

Try something like this.

Code:

int main(void)
{
#define     STR_SIZE      10
#define     ARRAY         5
    char    sInput[255],sArray[ARRAY][STR_SIZE+1];
    int     i,iLoops=0;

    //get the input
    //find the number of times to add to smaller
    //strings in array 
    iLoops=lstrlen(sInput)/STR_SIZE;
    //I would dynamicly(?) alloc the mem here
    //or at least check that it will fit the array
    // ie if ((iLoops >= ARRAY) == ERROR)
    for(i=0;i<iLoops;i++)
    {
        //add string
        strncpy( sArray[i], sInput+(i * STR_SIZE), STR_SIZE);
    }
return 0;
}

PS I have left a flaw in the logic because its Friday. (CRYPTIC HINT: Look at the ceiling, not the floor)

for(i = 0; i < 5; i++)
{
for(k = 0; k < 10; k++)
{
array[i][k] = string[p];
p++;
}
k = 0;
}