分类： C/C++
2009-01-05 00:21:51
#includeFind out what's going wrong.#define TOTAL_ELEMENTS (sizeof(array) / sizeof(array[0])) int array[] = {23,34,12,17,204,99,16};
int main()
{
int d;
for(d=-1;d <= (TOTAL_ELEMENTS-2);d++)
printf("%d\n",array[d+1]);
return 0;
}
#includevoid OS_Solaris_print() { printf("Solaris - Sun Microsystems\n"); } void OS_Windows_print() { printf("Windows - Microsoft\n"); } void OS_HP-UX_print() { printf("HP-UX - Hewlett Packard\n"); } int main() { int num; printf("Enter the number (1-3):\n"); scanf("%d",&num); switch(num) { case 1: OS_Solaris_print(); break; case 2: OS_Windows_print(); break; case 3: OS_HP-UX_print(); break; default: printf("Hmm! only 1-3 :-)\n"); break; } return 0; }
enum {false,true};
int main()
{
int i=1;
do
{
printf("%d\n",i);
i++;
if(i < 15)
continue;
}while(false);
return 0;
}
#includeWhat could be the reason?#include int main()
{
while(1)
{
fprintf(stdout,"hello-out");
fprintf(stderr,"hello-err");
sleep(1);
}
return 0;
}
#includeJust by looking at the program one "might" expect the output to be, the same for both the printf statements. But on running the program you get it as:#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;
}
#includeIf you expect the output of the above program to be NONE, I would request you to check it out!!int main()
{
int a=10;
switch(a)
{
case '1':
printf("ONE\n");
break;
case '2':
printf("TWO\n");
break;
defa1ut:
printf("NONE\n");
}
return 0;
}
int main()Why does it happen so?
{
int* p;
p = (int*)malloc(sizeof(int));
*p = 10;
return 0;
}
| Input | Output |
| 0 | 0(0000000) |
| 5 | 2(0000101) |
| 7 | 3(0000111) |
int CountBits (unsigned int x )Find out the logic used in the above program.
{
static unsigned int mask[] = { 0x55555555,
0x33333333,
0x0F0F0F0F,
0x00FF00FF,
0x0000FFFF } ;
int i ;
int shift ; /* Number of positions to shift to right*/ for ( i =0, shift =1; i < 5; i ++, shift *= 2)
x = (x & mask[i ])+ ( ( x >> shift) & mask[i]);
return x;
}
#includeint main() { float f=0.0f; int i; for(i=0;i<10;i++) f = f + 0.1f; if(f == 1.0f) printf("f is 1.0 \n"); else printf("f is NOT 1.0\n"); return 0; }
#includeint main() { int a = 1,2; printf("a : %d\n",a); return 0; }
#includeint main() { int i=43; printf("%d\n",printf("%d",printf("%d",i))); return 0; }
void duff(register char *to, register char *from, register int count)Is the above valid C code? If so, what is it trying to acheive and why would anyone do something like the above?
{
register int n=(count+7)/8;
switch(count%8){
case 0: do{ *to++ = *from++;
case 7: *to++ = *from++;
case 6: *to++ = *from++;
case 5: *to++ = *from++;
case 4: *to++ = *from++;
case 3: *to++ = *from++;
case 2: *to++ = *from++;
case 1: *to++ = *from++;
}while( --n >0);
}
}
int CountBits(unsigned int x)
{
int count=0;
while(x)
{
count++;
x = x&(x-1);
}
return count;
}
int foobar(void);The following programs should be of some help in finding the answer: (Compile and run both the programs and see what happens)
int foobar();
#includeProgram 2:void foobar1(void)
{
printf("In foobar1\n");
}
void foobar2()
{
printf("In foobar2\n");
}
int main()
{
char ch = 'a';
foobar1();
foobar2(33, ch);
return 0;
}
#includevoid foobar1(void)
{
printf("In foobar1\n");
}
void foobar2()
{
printf("In foobar2\n");
}
int main()
{
char ch = 'a';
foobar1(33, ch);
foobar2();
return 0;
}
#includeint main()
{
float a = 12.5;
printf("%d\n", a);
printf("%d\n", *(int *)&a);
return 0;
}
int arr[80];File2.c
extern int *arr;
int main()
{
arr[1] = 100;
return 0;
}
#includeint 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;
}
#define SIZE 10 void size(int arr[SIZE])
{
printf("size of array is:%d\n",sizeof(arr));
}
int main()
{
int arr[SIZE];
size(arr);
return 0;
}
#include#include void Error(char* s)
{
printf(s);
return;
}
int main()
{
int *p;
p = malloc(sizeof(int));
if(p == NULL)
{
Error("Could not allocate the memory\n");
Error("Quitting....\n");
exit(1);
}
else {
/*some stuff to use p*/ }
return 0;
}
#includeint main()
{
char c;
scanf("%c",&c);
printf("%c\n",c);
scanf(" %c",&c);
printf("%c\n",c);
return 0;
}
#includeint main()
{
char str[80];
printf("Enter the string:");
scanf("%s",str);
printf("You entered:%s\n",str);
return 0;
}
#includeint main()
{
int i;
i = 10;
printf("i : %d\n",i);
printf("sizeof(i++) is: %d\n",sizeof(i++));
printf("i : %d\n",i);
return 0;
}
#includevoid foo(const char **p) { }
int main(int argc, char **argv)
{
foo(argv);
return 0;
}
#includeint main()
{
int i;
i = 1,2,3;
printf("i:%d\n",i);
return 0;
}
#include#include #define MAX 80 #define NUMBER '0' int getop(char[]);
void push(double);
double pop(void);
int main()
{
int type;
char s[MAX];
while((type = getop(s)) != EOF)
{
switch(type)
{
case NUMBER:
push(atof(s));
break;
case '+':
push(pop() + pop());
break;
case '*':
push(pop() * pop());
break;
case '-':
push(pop() - pop());
break;
case '/':
push(pop() / pop());
break;
/* ... * ... * ... */ }
}
}
#include#include char t[]={
0,0,0,0,0,0,12,18,33,63,
33,33,62,32,62,33,33,62,30,33,
32,32,33,30,62,33,33,33,33,62,
63,32,62,32,32,63,63,32,62,32,
32,32,30,33,32,39,33,30,33,33,
63,33,33,33,4,4,4,4,4,4,
1,1,1,1,33,30,33,34,60,36,
34,33,32,32,32,32,32,63,33,51,
45,33,33,33,33,49,41,37,35,33,
30,33,33,33,33,30,62,33,33,62,
32,32,30,33,33,37,34,29,62,33,
33,62,34,33,30,32,30,1,33,30,
31,4,4,4,4,4,33,33,33,33,
33,30,33,33,33,33,18,12,33,33,
33,45,51,33,33,18,12,12,18,33,
17,10,4,4,4,4,63,2,4,8,
16,63 };
int main(int argc,char** argv)
{
int r,pr;
for(r=0;r<6;++r)
{
char *p=argv[1];
while(pr&&*p)
{
int o=(toupper(*p++)-'A')*6+6+r;
o=(o<0||o>=sizeof(t))?0:o;
for(pr=5;pr>=-1;--pr)
{
printf("%c",( ( (pr>=0) && (t[o]&(1<<pr)))?'#':' '));
}
}
printf("\n");
}
return 0;
}
#include#include #define SIZEOF(arr) (sizeof(arr)/sizeof(arr[0])) #define PrintInt(expr) printf("%s:%d\n",#expr,(expr)) int main()
{
/* The powers of 10 */ int pot[] = {
0001,
0010,
0100,
1000 };
int i;
for(i=0;i<SIZEOF(pot);i++)
PrintInt(pot[i]);
return 0;
}
#includeAlso implement a C function similar to the above to find the GCD of 4 integers.int gcd(int u,int v)
{
int t;
while(v > 0)
{
if(u > v)
{
t = u;
u = v;
v = t;
}
v = v-u;
}
return u;
}
int main()
{
int x,y;
printf("Enter x y to find their gcd:");
while(scanf("%d%d",&x, &y) != EOF)
{
if(x >0 && y>0)
printf("%d %d %d\n",x,y,gcd(x,y));
printf("Enter x y to find their gcd:");
}
printf("\n");
return 0;
}
#include#define PrintInt(expr) printf("%s : %d\n",#expr,(expr)) int main()
{
int y = 100;
int *p;
p = malloc(sizeof(int));
*p = 10;
y = y/*p; /*dividing y by *p */;
PrintInt(y);
return 0;
}
#includeint main()
{
int day,month,year;
printf("Enter the date (dd-mm-yyyy) format including -'s:");
scanf("%d-%d-%d",&day,&month,&year);
printf("The date you have entered is %d-%d-%d\n",day,month,year);
return 0;
}
#includeint main()
{
int n;
printf("Enter a number:\n");
scanf("%d\n",n);
printf("You entered %d \n",n);
return 0;
}
#include#define PrintInt(expr) printf("%s : %d\n",#expr,(expr)) int FiveTimes(int a)
{
int t;
t = a<<2 + a;
return t;
}
int main()
{
int a = 1, b = 2,c = 3;
PrintInt(FiveTimes(a));
PrintInt(FiveTimes(b));
PrintInt(FiveTimes(c));
return 0;
}
#include#define PrintInt(expr) printf("%s : %d\n",#expr,(expr)) int max(int x, int y)
{
(x > y) ? return x : return y;
}
int main()
{
int a = 10, b = 20;
PrintInt(a);
PrintInt(b);
PrintInt(max(a,b));
}
#includeWell fixing the above code is straight-forward. To make the problem interesting, you have to fix the above code, by changing exactly one character. There are three known solutions. See if you can get all those three.int main()
{
int i;
int n = 20;
for( i = 0; i < n; i-- )
printf("-");
return 0;
}
#includeint main()
{
int* ptr1,ptr2;
ptr1 = malloc(sizeof(int));
ptr2 = ptr1;
*ptr2 = 10;
return 0;
}
#includeint main()
{
int cnt = 5, a;
do {
a /= cnt;
} while (cnt --);
printf ("%d\n", a);
return 0;
}
#includeint main()
{
int i = 6;
if( ((++i < 7) && ( i++/6)) || (++i <= 9))
;
printf("%d\n",i);
return 0;
}
#include#include #define SIZE 15 int main()
{
int *a, i;
a = malloc(SIZE*sizeof(int));
for (i=0; i<SIZE; i++)
*(a + i) = i * i;
for (i=0; i<SIZE; i++)
printf("%d\n", *a++);
free(a);
return 0;
}
#includeint main()
{
int a=3, b = 5;
printf(&a["Ya!Hello! how is this? %s\n"], &b["junk/super"]);
printf(&a["WHAT%c%c%c %c%c %c !\n"], 1["this"],
2["beauty"],0["tool"],0["is"],3["sensitive"],4["CCCCCC"]);
return 0;
}
#includeint main()
{
char dummy[80];
printf("Enter a string:\n");
scanf("%[^a]",dummy);
printf("%s\n",dummy);
return 0;
}
int a;b.c
int a = 10;main.c
extern int a;
int main()
{
printf("a = %d\n",a);
return 0;
}
Let's see what happens, when the files are compiled together: bash$ gcc a.c b.c main.c bash$ ./a.out a = 10Hmm!! no compilation/linker error!!! Why is it so??
#define offsetof(a,b) ((int)(&(((a*)(0))->b)))
#define SWAP(a,b) ((a) ^= (b) ^= (a) ^= (b))What are the potential problems with the above macro?
#define DPRINTF(x) printf("%s:%d\n",#x,x)
int IAddOverFlow(int* result,int a,int b)So, how do you code the above function? (To put in a nutshell, what is the logic you use for overflow detection?)
{
/* ... */ }
#define ROUNDUP(x,n) ((x+n-1)&(~(n-1)))
#define isupper(c) (((c) >= 'A') && ((c) <= 'Z'))But there would be a serious problem with the above definition of macro, if it is used as follows (what is the problem??)
char c;But most of the libraries implement the isupper (declared in ctypes.h) as a macro (without any side effects). Find out how isupper() is implemented on your system.
/* ... */ if(isupper(c++))
{
/* ... */ }
int VarArguments(...)
{
/*....*/ return 0;
}
const char *p;
char* const p;