c pointer

     void foo1() { int i = 10; }

     void foo2() { int i = 10; }

     int main() {
         void *f1 = &foo1;
         void *f2 = &foo2;
         printf("bytes: %d\n", (unsigned int)foo1 - (unsigned int)foo2);
     }

---
C types

   printf("char: %dB\nint: %dB\nunsigned int: %dB\nlong long: %dB\n",
   sizeof(char), sizeof(int), sizeof(unsigned int), sizeof(long long));

---
C array


    int a[3] = {1, 2, 3};    // an array of 3 int's
    char b[3] = {'a', 'b', 'c'};  // an array of 3 char's

    int main() {
      // first element is at index 0
      printf("%d\n", a[0]);

      a[1] += 1;  // use index access
      *(a+2) = 5; // pointer access

      printf("%d %d\n", a[1], a[2]);

      // pointers to array elements
      printf("a %p a1 %p a2 %p a2 %p\n", a, a+1, a+2, &a[2]);

      // pointer arithmetic uses type
      printf("%p %p\n", b, b+1);

      return 0;
    }


---
little-endian


    int main() {
        unsigned int x = 0xdeadbeef;
        char *byte = (char *)&x;

        for (int i=0;i<4; i++) {
            printf("[%d-bit]: %x", i, (unsigned int)byte[i]);
        }
        return 0;
    }

---
little-endian casting

    long long  val64 = 0x123456789abcdef;
    int *ptr32 = (int*) &val64;
    printf("what do you expect? 0x%x\n", *ptr32);