how this code works

[codelife]

I'm workig on memory allocation and trying to understand this code.

output prints
i=0
d=149909512 - How is d getting these numbers?
*d=0,
i=5, d[i]135145.
how can d have these numbers if malloc returns the address of the beginning of allocated memory or NULL if it fails.

#include<stdio.h>

int main(void)
{
    int i, *d;
        /*printf("%d\n %d",i,*d);*/
    d =  malloc( 5 * sizeof(int) );
    printf("i=%d\n d=%d\n *d=%d\n",i,d,*d);
    
    for(i = 0; i < 5; i++)
    d[i] = i + 100;
    printf("i=%d\n d[i]%d",i,d[i]);
        
}

[weaknessforcats]

The for loop exits with i == 5. When i is 4 the ++i has occurred before i < 5 is tested.

I suggest a pair of braces around the loop so both the assignment and printf are inside the loop

[donbock]

You are using the "%d" format specifier to print the value of d. That format specifier should only be used with int arguments. Use "%p" for pointers.

You should test the value of d and be careful not to dereference it if the value is NULL.

Your first printf prints the value of *d before it has been initialized. The value of an uninitialized variable is unpredictable. You can avoid this problem by using calloc instead of malloc.