Why can't memset initialize array elements to 1?

Today I found a very serious problem

memset Function cannot assign an array to 1
Looking up the data, I found ,memset The function is filled byte by byte , Complement in computer ,memset Functions can only be filled with all 0 Or all 1.

explain ,memset The function can only assign a full value to an array 0, Or all -1.

#include<string.h>
int main(){
    
	int a[101];
	memset(a,1,sizeof(a));
	for(int i=1;i<=100;i++)
		cout<<a[i]<<endl;
	return 0;
}

The author found that the printed ones are not all 1, But not for 0 The positive integer (16843009)！

See blog for details ：
https://www.cnblogs.com/blogofwu/p/4140563.html