enum takes the format like {0,1,2..}

Hence A=0, B=1, C=2

student1 = A (value is 0)

student2 = B (value is 1)

student3 = C (value is 2)

Hence it prints 0, 1, 2

extern keyword in C / C++ is used before any variable to specify that, this variable is from external file / program, it's memory has been allocated by that program. In current program, we want to get is its address only to work upon it.

In given program, when compiler will try to get address of i it will throw an error, at the time of linking, because there is no other program which is allocating memory of i.

extern int x; - Tells compiler that, x is defined in another file, hence compiler will try to fetch that value. However, It will fail as there is no such file / program, which provides definition of x.

Further,

 int x = 98; - Provides definition of x.

Compiler will take this value of x and print 98. Reason for this behaviour is, in C / C++ whenever, there is conflict between definition of variable, local variable is given higher priority than external variable, and it overrides the definition of external variable.

Size of pointer type variable is 4 bit on GCC compiler on 64 bit machine.

If Elements of an automatic structure are partially initialized, non initialized elements are given a default value of 0.

In C/C++, local variable is given higher priority over global variable. Here, variable gloabalVariable is conflicting, hence, local variable is given higher priority and local value 80 would be printed rather than 83.

We can break it down like this:

x = 36

y = 89

hence x < y will be true i.e. 1

Now, z = 15

hence 1 < 15 would be true i.e. 1

Which will result in m = 1

It will throw error during compilation, due to conflict in parameters declaration on func().

Whenever we partially initialize an integer array, uninitialized values get assigned to a default value of 0.  

In for loop, scanf is at the place where condition is checked before execution of for loop. scanf will return an integer value of whatever input is given, which will always be treated as true, further this value will be printed and loop will again ask for input. This will lead to an infinite loop.

Inside the block, new definition of 'i' will override previous definition because local variable is given higher priority, in case of conflict. However, it's scope is limited to current block only. Hence, upon first printf local value i.e. 5 will be printed and outside of block, 9 would be printed.

Values from ch[0] and ch[1] would be printed as whatever is assigned. 

For x.i it will print the sum of entire union. 

Values of union is calculated as per above image.

hence, sum of union would be 512 + 4 + 2 + 1 = 519

i.e, x would become 519.

On GCC compiler it will print 'HackersFriend', but during compilation, it will give warning saying, warning: conflicting types for 'print'

It won't compile on GCC compiler.

It will throw following error:

error: variable or field 'x' declared void

There is syntax error on line 'car int myCarPrice'

Correct way to create an instance of car would be as follows:

struct car myCar

Then if we need to define value of car price, we can do as follows:

myCar.price = 700000

typedef is used to give a new name to an existing data type. Here, days would become new name for enum weekdays.

While compiling, this code will throw error. Reason for this is, prototype of foo() is not declared. We can add it's prototype before calling it, to fix this error.

The fixed code would look like following:

#include<stdio.h>

int foo();

int main()
{
    int (*x)() = foo;
    (*x)();
    return 0;
}
int foo()
{
    printf("HackersFriend");
    return 0;
}

Upon execution, this will print HackersFriend.