What compiler is doing when we pass unnecessary parameters in scanf

Hi,
In the second scenario what value is it printing when i have given extra parameter in scanf?
Does it vary from compiler to compiler?

Scenario : I
-------------
root@kaushik_Fedora11 ~/C/LET_US_C/ch-1> cat simple-interest.c #include

void main ()

{
        int p;
        float i=0;
        printf ("enter the principal amount\n");
        scanf ("%d",&p);
        i = (p*5*5)/100;
        printf ("Interterest is : %f\n",i);
}

root@kaushik_Fedora11 ~/C/LET_US_C/ch-1> ./a.out
enter the principal amount
100
Interterest is : 25.000000

Scenario : II
-------------

#include

void main ()

{
        int p;
        float i=0;
        printf ("enter the principal amount\n");
        scanf ("p:%d",&p);
        i = (p*5*5)/100;
        printf ("Interterest is : %f\n",i);
}

root@kaushik_Fedora11 ~/C/LET_US_C/ch-1> ./a.out
enter the principal amount
100
Interterest is : -9321198.000000

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