C programs post4

Q 16.)

#include
using namespace std;

class Base {
public:
Base()
{
foo();
}

virtual void f()
{
cout << "\nBase::f is being called\n";
}

void foo()
{
f();
}
};

class Derive : public Base {
public:
virtual void f()
{
cout << "\nDerive::f is being called\n";
}
};

int main()
{
Derive d; //Base::f is being called.. f being virtual.. Why derived f() is not being called..
}

why output is not expected..




Q.17)

int main()
{
int i=10, j=2;
int *ip= &i, *jp = &j;
int k = *ip/*jp;
printf("%d",k);
return 0;
}

Is it a valid c-program ? Give reasons.






Q.18)

int main()
{
float f=5,g=10;
enum{i=10,j=20,k=50};
printf("%d\n",++k);
printf("%f\n",f<<2);
printf("%lf\n",f%g);
printf("%lf\n",fmod(f,g));
}

What is the problem with this code ?





Q.19)

What is the output of this two codes:

int main()
{
signed char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}

int main()
{
unsigned char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}


Why is the difference?





Q.20)

int main()
{
char i=0;
for(;i>=0;i++) ;
printf("%d\n",i);
}

Is it a valid C program ? Give reasons.

Continue

C programs post3

Q 11.)
Is there a way to multiply two matrix in less than O(n^3) time complexity..

For this Q algorithm was asked, if you guys don't know the answer then make a comment below and I will tell the answer or just take some efforts to search it.



Q 12.)

#include
using namespace std;

int main()
{
int a,c,foo;
char *p;
cin>>a>>c;// give two numbers..

p=(char *)a;
foo= (int)&p[c];
cout<return 0;
}

what this code snippet does...
even if u get the answer explain the logic.
without executing




Q 13.)

whats wrong with this program..

#include
using namespace std;

class foo
{
const int a;
public:
foo():a(10)
{}

void show()
{
cout<}
};

int main()
{
const foo obj;
obj.show();
}



Q 14.)

#include
using namespace std;

int main()
{
int *p,*c;
p=(int*)10;
c=(int*)20;
cout<<(int)p<<(int)c;
}

is this a valid program..
if no why..
if yes why..




Q 15.) #include
using namespace std;

int main()
{
void *vptr = malloc(sizeof(int)*2);
int p;
p=(int)vptr;
*((int*)p +0)=9;
*((int*)p +1)=10;
cout<<1[(int*)vptr]; }

comment on this program and write the output if any

Continue

C programs post2

Q 6.)
#include
int main()
{
int a=3, b = 5;

printf(&"Ya!Hello! how is this? %s\n"[a], &b["junk/super"]);
printf(&"WHAT%c%c%c %c%c %c !\n"[a], 1["this"],
2["beauty"],0["tool"],0["is"],3["sensitive"],4["CCCCCC"]);
return 0;
}


is this a valid c program....



Q 7.)
The following C program segfaults of IA-64, but works fine on IA-32.

int main()
{ int* p;
p = (int*)malloc(sizeof(int));
*p = 10;
return 0; }


Why does it happen so?



Q 8.)

#include
#define f(a,b) a##b
#define g(a) #a
#define h(a) g(a)

int main()
{
printf("%s\n",h(f(1,2)));
printf("%s\n",g(f(1,2)));
return 0;
}

guess the output...




Q 9.)

#include
int main()
{
int a = 1,2;
printf("a : %d\n",a);
return 0;
}


is this valid C program..
if yes..
what is the output of this C program..
say it without executing..
silly question..



Q 10.)
if this happens that u have to multiply a number by 7 without using * sign..
which of the answer u will choose..
justify ur answer....

x = (x<<3)-x;

or

x=(x<<2) + (x<<1) + x

Continue

C programs post1

Q1.)

#include
#define TOTAL_ELEMENTS (sizeof(array) / sizeof(array[0]))
int array[] = {23,34,12,17,204,99,16};

int main()
{
signed int d;
printf("Total Elements in the array are => %d\n",TOTAL_ELEMENTS);
for(d=-1;d <= (TOTAL_ELEMENTS-2);d++)
printf("%d\n",array[d+1]);
printf("Did u see the output..");
return 0;
}


Q 2.) File1.c 1 int arr[80]; File2.c extern int *arr;
int main()
{
arr[1] = 100;
return 0;
}
what should be the output..


Q 3.) #include
int main()
{
int a=1;
switch(a)
{ int b=20;
case 1: printf("b is %d\n",b);
break;
default:printf("b is %d\n",b);
break;
}
return 0;
}



Q.4)
#include
#include
void Error(char* s)
{
printf(s);
return;
}

int main()
{
int *p;
p = (int*)malloc(sizeof(int));
if(!p)
{
Error("memory error");
Error("Quitting....\n");
exit(1);
}
else
{
/*some stuff to use p*/
}
free(p);
return 0;
}

Find potential problem with the error function.. a security concern..






Q 5.)
Easy..
#include
int main()
{
char c;
scanf("%c",&c);
printf("%c\n",c);
scanf(" %c",&c);//see space before %c
printf("%c\n",c);

return 0;
}

why this runs perfect..
but fails in this program..

#include
int main()
{
char c;
scanf("%c",&c);
printf("%c\n",c);
scanf("%c",&c);//no space this time..
printf("%c\n",c);

return 0;
}

Even though we know that white spaces are ignored..
which include space, newline and tab..
so why the second time output is not desired..

Continue