Why doesn't %zd printf format work in VS2010?

Following piece of my code does not print the value in visual studio.

int main() { 
    intptr_t P = 10;
    printf("test value is %zd",P);
    return 0;
}

OUTPUT:

test value is zd

I expect the the above code print

test value is 10

i am using intptr_t instead of integer so as to make the code to adjust in both the 32 bit and 64 bit architecture.