Initializing entire array with memset

Question

I have initialised the entire array with value 1 but the output is showing some garbage value. But this program works correctly if i use 0 or -1 in place of 1. So are there some restrictions on what type of values can be initialised using memset.

 int main(){
    int a[100];
    memset(a,1,sizeof(a));
    cout<<a[5]<<endl;
    return 0;
    }

Answer 1

memset, as the other say, sets every byte of the array at the specified value.

The reason this works with 0 and -1 is because both use the same repeating pattern on arbitrary sizes:

(int) -1 is 0xffffffff
(char) -1 is 0xff

so filling a memory region with 0xff will effectively fill the array with -1.

However, if you're filling it with 1, you are setting every byte to 0x01; hence, it would be the same as setting every integer to the value 0x01010101, which is very unlikely what you want.