Consider the following C declarations:
struct node {
int i;
float j;
};
struct node *s[10];Which of the following describes 's'?
In 'struct node *s[10]', array subscript operator [] has higher precedence than dereference *. Thus, 's' is an array of 10 elements, where each element is a pointer to 'struct node'.
Which choice is printed when the following program is executed?
#include <stdio.h>
struct test {
int i;
char *c;
} st[] = {5, "become", 4, "better", 6, "jungle", 8, "ancestor", 7, "brother"};
int main(void) {
struct test *p = st;
p += 1;
++p->c;
printf("%s,", p++->c);
printf("%c,", *++p->c);
printf("%d,", p[0].i);
printf("%s", p->c);
return 0;
}p initially points to st[0]. p += 1 points to st[1] ({4, 'better'}). ++p->c advances 'better' to 'etter'. p++->c prints 'etter' and post-increments p to st[2] ({6, 'jungle'}). ++p->c in *++p->c modifies p->c from 'ancestor' to 'ncestor' and evaluates to 'n' (wait, ++p advances to st[3], c='ancestor' -> ++c is 'ncestor', * is 'n'). Next p[0].i is st[3].i which is 8. p->c is 'ncestor'. So output is 'etter, u, 8, ncestor'.
Consider the following C typedef and functions:
typedef struct {
char *a;
char *b;
} t;
void f1(t s) {
s.a = "U";
s.b = "V";
}
void f2(t *p) {
p->a = "V";
p->b = "W";
}
int main(void) {
static t s = {"A", "B"};
f1(s);
printf("%s %s ", s.a, s.b);
f2(&s);
printf("%s %s", s.a, s.b);
return 0;
}f1(s) receives a structure by value (copy), so modifications to s.a and s.b inside f1 do not affect main's 's'. Thus first print outputs 'A B'. f2(&s) receives pointer to 's' (pass by reference) and updates s.a and s.b to 'V' and 'W', so second print outputs 'V W'.
What is the size of the following C union on a 32-bit system where int is 4 bytes?
union Data {
int i;
char str[20];
double d;
};In a C union, all members share the same memory location, and the total size of the union is equal to the size of its largest member. 'str[20]' occupies 20 bytes (larger than double's 8 bytes and int's 4 bytes), so sizeof(union Data) is 20 bytes.
Consider structure question #5:
struct Item_5 {
int id;
char name[10];
};
struct Item_5 it = {5, "GATE"};
struct Item_5 *ptr = ⁢What is the value of 'ptr->id'?
The pointer 'ptr' targets structure instance 'it'. Dereferencing via 'ptr->id' retrieves the value assigned to field 'id', which is 5.