一直报错，C语言入门，如何解决？

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

char* strcpy(char* strDest, const char* strSrc)
{

 char* address = strDest;
 while ((*strDest++ = *strSrc++) != '\0');
 return address;

}

int main()
{

char a[100], b[100], * p;
scanf_s("%c", &a,100);
p=strcpy(b, a);
printf("%c", b);
return 0;

}

报错Run-Time Check Failure #2 - Stack around the variable 'a' was corrupted.

是不是是scanf_s("%c",&a[i],100);