i am getting bunch (null) printed

Question

here is my source code

#include <stdio.h>

int a[175];
int b[174];
int step[174];
int i ;
int c ;
int j ;
int k ;
int z ;
int max ;
int main()
{
for (i = 0; i < 5 ; i++)
{
printf("%s%d%s", "\n enter the number #",i," :");
scanf("%d",&a[i]);
}

for ( j = 0; j <5 ; j++)
{
if (j==0)
{
printf("\n\n\n\n\n...");
//
//b[0] = 0 ;
}

if (j>0)
{
b[j] = a[j+1] - a[j];
}
}

for ( k = 0; k < 5 ; k++)
{
b[k] = step[k];
}

max = step[0];

/* for (c = 1; c< 5 ; c++)
{
if (step[c] > max)
max = step[c];
}
*/

// printf("%s,%d"," \n \n the highest diffenece in number is : ",max);
//printf("%s","\n\n\n the highest diffenece is : ");
//printf("%d",max);

for (z = 0; z < 5; z++)
{

printf("%s",step[z]);

}

system("pause");

return 0;
}