C quiz

void printbinary(int v)
{
    unsigned int mask=1<<((sizeof(int)<<3)-1);
    while(mask) {
        printf("%d", (v&mask ? 1 : 0));
        mask >>= 1;
    }
    printf("\n");
}

    int a = 0;
    // how to set set the 5th bit to 1?
    printbinary(a);


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C quiz:

    int x = 0;
    char* c_ptr= (void*)&x;
    c_ptr[3] = 1;
    printf("0x%x\n", x);

---
little-endian

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

    for (int i=0;i<4; i++) {
        printf("[%d-bit]: %x\n", 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);

---
C pointers


    int g = 3;

    int main() {
      int l = 5;  // local variables don't have a default value
      int *p, *q;

      // take address of variable
      p = &g;
      q = &l;
      printf("p %p q %p\n", p, q);

      // pointer of an pointer
      int **pp;
      pp = &p;    // take address of a pointer variable
      printf("pp %p %p %d\n", pp, *pp, **pp);

      int (*f)(int, char **);
      f = &main;  // take address of a function
      printf("main: %p\n", f);

      return 0;
    }

---
uninit local var

    void bar() {
      int l;  // local variables don't have a default value
      printf("uninitialized local variable: %x\n", l);
    }

    void foo() {
        int xyz = 0xdeadbeef;
        printf("quit foo w/ local var = %x\n", xyz);
    }


---
pointer arithmetic

   int main() {
    char *c = (char *)0x08200000;
    int  *i = (int *) 0x08200000;

    printf("%p %p\n", (c+1), (i+1));

     return 0;
   }

---
C arrays


    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;
    }

---
OS using Go:
https://pdos.csail.mit.edu/papers/biscuit:login19.pdf

---

Using TensorFlow for Deep Learning on Video Data:
https://blog.tensorflow.org/2023/01/using-tensorflow-for-deep-learning-on-video-data.html