Can anybody tell me why this is happening in c language

Question

 #include 
 //Compiler version gcc 6.3.0

 int main(void)
 {

     float a=10;
    printf(\"%f\"+1,a);

    return 0;
 }

Output -- d

Answer 1

The output is different every time because it is undefined to read from an unknown address.

Compare with this code:

#include 

int main(){

   printf("Hello,World\n"+1);
}

It looks like the famous Hello,World but in fact it is the less known version ello,World. The argument to printf is string or more precisely a pointer to a null terminated sequence of chars in memory, when "Hello"+1 is evaluated, the pointer is incremented by one and points to "ello,World".

Your program will first print the the string "f" and in the second case is a memory overrun error, it will print whatever is found in the memory location 36 bytes away from the string. This random memory location is likely to have a different contents every time.