Script started on Mon Oct 26 17:29:22 2026
Restored session: Wed Oct 21 18:42:01 EDT 2026
macbook:Desktop> cat q16.c 
#include <stdio.h>
#include <string.h>
#define NAME_LEN 100

typedef struct {
    int number;
    char name[NAME_LEN + 1];
} Part;

int main() {
    Part part1, part2;

    strncpy(part1.name, "hammer", 7);
    part2 = part1;
    // Question: what will this print?
    printf("%s\n", part2.name);

    return 0; 
}
macbook:Desktop> gcc q16.c
macbook:Desktop> ./a.out
hammer
macbook:Desktop> cat float_in_hex.c
cat: float_in_hex.c: No such file or directory
macbook:Desktop> cd csc3320_Fall2026/programs/C_ch16
macbook:C_ch16> cat float_in_hex.c                 
// How does a float look internally?
// -MCW

#include <stdio.h>


union {
  float value;
  unsigned char  bytes[4];
} my_union;



int main() {

  my_union.value = 10.7;

  printf("float value is %f \n", my_union.value);
  printf("float value in hex is ");
  for (int i=0; i<4; i++) 
    printf("%2x ", my_union.bytes[i]);
  printf("\n");

  my_union.value = 10.8;
  printf("float value is %f \n", my_union.value);
  printf("float value in hex is ");
  for (int i=0; i<4; i++) 
    printf("%2x ", my_union.bytes[i]);
  printf("\n");

  return 0;
}
macbook:C_ch16> gcc float_in_hex.c 
macbook:C_ch16> ./a.out
float value is 10.700000 
float value in hex is 33 33 2b 41 
float value is 10.800000 
float value in hex is cd cc 2c 41 
macbook:C_ch16> cat sizeof_union_struct.c
// Show the sizes of the union vs struct
#include <stdio.h>

int main() {

    union {
        int i;
        float f;
        char c;
        double val;
        long L_val;
    } u;

    struct {
        int i;
        float f;
        char c;
        double val;
        long L_val;
    } s;

  // Do not need to assign values, since we just want to see size

  printf("Size of struct s is %lu\n", sizeof(s));
  printf("Size of union u is %lu\n", sizeof(u));

  return 0;
}
macbook:C_ch16> gcc sizeof_union_struct.c
macbook:C_ch16> ./a.out
Size of struct s is 32
Size of union u is 8
macbook:C_ch16> cat C_ch16_8_v2.c 
#include <stdio.h>

int main() {

    union {
        int i;
        float f;
    } u;

    struct {
        int i;
        float f;
    } s;

  s.i = 3;
  s.f = 5.6;
  printf("s.i is %d \n", s.i);
  printf("s.f is %f \n", s.f);

  u.i = 3;
  u.f = 5.6;
  printf("u.i is %d \n", u.i);
  printf("u.i is %x in hex\n", u.i);
  printf("u.f is %f \n", u.f);

  return 0;
}
macbook:C_ch16> gcc C_ch16_8_v2.c 
macbook:C_ch16> ./a.out
s.i is 3 
s.f is 5.600000 
u.i is 1085485875 
u.i is 40b33333 in hex
u.f is 5.600000 
macbook:C_ch16> cp float_in_hex.c float_in_hex_v2.c
macbook:C_ch16> vi float_in_hex_v2.c 
macbook:C_ch16> gcc float_in_hex_v2.c 
macbook:C_ch16> ./a.out
float value is 5.600000 
float value in hex is 33 33 b3 40 
macbook:C_ch16> cat float_in_hex_v2.c 
// How does a float look internally?
// -MCW

#include <stdio.h>


union {
  float value;
  unsigned char  bytes[4];
} my_union;



int main() {

  // see C_ch16_8_v2.c
  my_union.value = 5.6;

  printf("float value is %f \n", my_union.value);
  printf("float value in hex is ");
  for (int i=0; i<4; i++) 
    printf("%2x ", my_union.bytes[i]);
  printf("\n");

  return 0;
}
macbook:C_ch16> cat C_ch16_11.c
/*
  See Kim King's book, page 403.
  This is an expanded example with code added by Michael Weeks.
*/
#include <stdio.h>

enum {CLUBS, DIAMONDS, HEARTS, SPADES} s;

void print_suit(int s1) {
  switch (s1) {
    case CLUBS:
      printf("Clubs");
      break;
    case DIAMONDS:
      printf("Diamonds");
      break;
    case HEARTS:
      printf("Hearts");
      break;
    case SPADES:
      printf("Spades");
      break;
    default:
      printf("Unknown");
  }
}

int main() {
  int i;

  i = DIAMONDS;   /* i is now 1               */
  printf("i = %d, which is ", i);
  print_suit(i);  
  printf("\n");

  s = 0;          /* s is now 0 (CLUBS)       */
  printf("s = %d, which is ", s);
  print_suit(s);  
  printf("\n");

  s++;            /* s is now 1 (DIAMONDS)    */
  printf("s = %d, which is ", s);
  print_suit(s);  
  printf("\n");

  i = s + 2;      /* i is now 3               */
  printf("i = %d, which is ", i);
  print_suit(i);  
  printf("\n");

  return 0;
}
macbook:C_ch16> gcc C_ch16_11.c
macbook:C_ch16> ./a.out
i = 1, which is Diamonds
s = 0, which is Clubs
s = 1, which is Diamonds
i = 3, which is Spades
macbook:C_ch16> 
macbook:C_ch16>  cat C_ch16_12.c 
struct point {
    int x;
    int y;
};
struct rectangle {
    struct point upper_left, lower_right;
};

macbook:C_ch16> cp C_ch16_12.c find_area.c
macbook:C_ch16> echo "#include <stdio.h>" >> find_area.c 
macbook:C_ch16> echo "int main() {" >> find_area.c
macbook:C_ch16> echo "return 0;" >> find_area.c
macbook:C_ch16> vi find_area.c 
macbook:C_ch16> gcc find_area.c
find_area.c:14:20: error: parameter 'my_rect' was not declared, defaults to 'int'; ISO C99 and later do not support implicit int [-Wimplicit-int]
   14 | float compute_area(my_rect) {
      |                    ^
find_area.c:17:18: error: member reference base type 'int' is not a structure or union
   17 |     pt1 = my_rect.upper_left;
      |           ~~~~~~~^~~~~~~~~~~
find_area.c:18:18: error: member reference base type 'int' is not a structure or union
   18 |     pt2 = my_rect.lower_right;
      |           ~~~~~~~^~~~~~~~~~~~
find_area.c:14:7: warning: a function definition without a prototype is deprecated in all versions of C and is not supported in C23 [-Wdeprecated-non-prototype]
   14 | float compute_area(my_rect) {
      |       ^
find_area.c:46:28: error: passing 'struct rectangle' to parameter of incompatible type 'int'
   46 |     my_area = compute_area(my_rect);
      |                            ^~~~~~~
1 warning and 4 errors generated.
macbook:C_ch16> vi find_area.c 
macbook:C_ch16> gcc find_area.c
macbook:C_ch16> ./a.out
  the area is 9.000000
macbook:C_ch16> cat find_area.c 
#include <stdio.h>


struct point {
    int x;
    int y;
};
struct rectangle {
    struct point upper_left, lower_right;
};



float compute_area(struct rectangle my_rect) {
    struct point pt1;
    struct point pt2;
    pt1 = my_rect.upper_left;
    pt2 = my_rect.lower_right;

    return (pt2.x - pt1.x) * (pt1.y - pt2.y);
}

/* 
    |
    |        * (7,6)
    |
    |           * (10,3)
    |
    -------------------
*/

int main() {

    struct rectangle my_rect;
    struct point pt;

    pt.x = 7;
    pt.y = 6;
    my_rect.upper_left = pt;
 
    pt.x = 10;
    pt.y = 3;
    my_rect.lower_right = pt;

    float my_area;
    my_area = compute_area(my_rect);
    printf("  the area is %f\n", my_area);

    return 0;
}
macbook:C_ch16> vi find_area.c 
macbook:C_ch16> cat find_area.c 
#include <stdio.h>


struct point {
    int x;
    int y;
};
struct rectangle {
    struct point upper_left, lower_right;
};



float compute_area(struct rectangle my_rect) {
    struct point pt1;
    struct point pt2;
    pt1 = my_rect.upper_left;
    pt2 = my_rect.lower_right;

    return (pt2.x - pt1.x) * (pt1.y - pt2.y);
}

/* 
    |
    |        * (7,6)
    |
    |            * (11,3)
    |
    -------------------
*/

int main() {

    struct rectangle my_rect;
    struct point pt;

    pt.x = 7;
    pt.y = 6;
    my_rect.upper_left = pt;
 
    pt.x = 11;
    pt.y = 3;
    my_rect.lower_right = pt;

    float my_area;
    my_area = compute_area(my_rect);
    printf("  the area is %f\n", my_area);

    return 0;
}
macbook:C_ch16> gcc find_area.c
macbook:C_ch16> ./a.out        
  the area is 12.000000
macbook:C_ch16> exit

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Script done on Mon Oct 26 18:45:10 2026