Making y[i] a modifiable variable in C

Making y[i] a modifiable variable in C

I am building a program that randomly generates a password using the ascii
tabe of values and can only contain one of each char. it generates a
password that is 8 char long.
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#define SIZE 10
char Charactor(char x);
void Check(char* y);
int main()
{
char string[SIZE];//defines varriables
char* point;
point=&string[SIZE];
srand(time(NULL));
for (int i=0;i<SIZE-1;i++)//empties out the string
{
string[i]='\0';
}
for (int i=0;i<SIZE-2;i++)//randomizes a char for each space in the string
{
string[i]=Charactor(*point);
}
Check(point);/checks the string for duplicated values
printf("%s\n",string);//prints string on screen
}
char Charactor(char x)
{
int rnd=0;
rnd=rand()%2;//chooses char or number using ascii
if (rnd==0)
{
rnd=rand()%10+48;
}
else
{
rnd=rand()%26+65;
}
x=(char)rnd;
return x;
}
void Check(char* y)
{
int run=0;
for (int i=0; i<SIZE-2;i++)
{
for (int x=0; x<SIZE-2; x++)
{
the line below is where I am having the issues.
if (y[i]==y[x] && run=0)
I keep getting an error saying that char* y must be a modifiable value.
{
run++;
continue;
}
else
{
y[i]='\0';
y[i]=Charactor(*y);
}
}
}
return;
}