How do you free allocated memory?
Answer: B
Correct answer: free(var-name);
free() returns memory obtained from malloc, calloc or realloc to the heap. delete is the C++ operator, and the other two names do not exist. Freeing the same block twice, or using a pointer after freeing it, is undefined behaviour.
Please log in or register to report this question.
The above C declaration define 's' to be
struct node
{
int i;
float j;
};
struct node *s[10];
Answer: A
Correct answer: An array, each element of which is a pointer to a structure of type node
Subscript binds tighter than the dereference, so struct node *s[10] groups as struct node *(s[10]) - an array of 10 pointers, each to a struct node. A pointer to an array would need parentheses in the other place: struct node (*s)[10].
Please log in or register to report this question.
What is the output of this program?
#include <stdio.h>
void main()
{
struct demo{
char * a;
int n;
};
struct demo p = {"hello", 2015};
struct demo q = p;
printf("%d", printf("%s",q.a));
}
Answer: C
Correct answer: hello5
The inner printf runs first, writing hello and returning 5 - the number of characters it wrote. The outer printf then prints that return value. So the output is hello5, in that order. (The assignment q = p copies the structure, including the pointer, so both point at the same string.)
Please log in or register to report this question.
What will be the output of the program if it is executed like below?
cmd> sample
/* sample.c */
#include <stdio.h>
int main(int argc, char **argv)
{
printf("%s\n", argv[argc-1]);
return 0;
}
Answer: A
Correct answer: sample
argv[0] is the program name as invoked, and with no further arguments argc is 1 - so argv[argc-1] is argv[0], which prints sample. The array always has argc entries plus a null pointer at argv[argc].
Please log in or register to report this question.
Members of a union are accessed as ________________
Answer: C
Correct answer: Both a & b
A union member is reached exactly as a structure member is: with the dot through a variable (u.member) and with the arrow through a pointer (p->member). The syntax is identical; only the storage layout differs.
Please log in or register to report this question.
The number of distinct nodes the following struct declaration can point to is
struct node
{
struct node *left;
struct node *centre;
struct node *right;
};
Answer: A
Correct answer: All of the above
The structure holds three pointers, so at most it points to three nodes - but nothing requires them to be different. Two of the pointers may hold the same address, or all three may, so the number of distinct nodes reached may be 1, 2 or 3. All the counts offered are possible.
Please log in or register to report this question.
#include <stdio.h>
typedef enum{
Male, Female=-1
}SEX;
int main()
{
SEX var = Male;
SEX var1 = Female;
printf("%d %d",var, var1);
return 0;
}
Answer: D
Correct answer: 0 -1
Male takes the default first value, 0, and Female is then explicitly set to -1. Explicit values may be given in any order and may be negative - the compiler only fills in the ones you leave out, continuing from the last value given.
Please log in or register to report this question.
Which of the following accesses a variable in structure b?
Answer: B
Correct answer: b.var;
b is a structure variable, so its members are reached with the dot: b.var. The arrow is for pointers.
Please log in or register to report this question.
What is the output of this program?
#include <stdio.h>
int main()
{
union demo {
int x;
int y;
};
union demo a = 100;
printf("%d %d",a.x,a.y);
}
Answer: D
Correct answer: Compilation Error
A union cannot be initialised from a bare value: union demo a = 100; is rejected, because the compiler must be told which member is meant. union demo a = {100}; would initialise the first member, and {.y = 100} would name it explicitly.
Please log in or register to report this question.
What is the output of this program?
#include <stdio.h>
void main()
{
struct number
{
int no;
char name[20];
};
struct number s;
s.no = 50;
printf("%d", s.no);
}
Answer: D
Correct answer: 50
Declaring the structure type inside a function is legal - it is simply local to that block. The member is set and printed, giving 50.
Please log in or register to report this question.