Interesting C Program -11

Want to know my name?



char a[5][6] = {
{0xe,0x6,0x8,0x6,0x7,0xe},
{0x9,0x9,0x8,0x9,0x2,0x4},
{0xe,0xf,0x8,0xf,0x2,0x4},
{0x9,0x9,0x8,0x9,0xa,0x4},
{0xe,0x9,0xe,0x9,0x4,0xe}
};
m[4]={0x8,0x4,0x2,0x1};
int main()
{
int i,j,k;
do
{
j=0;
do
{
k=0;
do
{
(a[i][j]&m[k])?printf("#"):printf(" ");
}while(++k<4);
printf(" ");
}while(++j<6);
printf("\n");
}while(++i<5);

}


Interesting C Program -10

Quine Program: (A C Program that prints itself)


/*quine.c*/
#include"stdio.h"
int main()
{
FILE *fp1;
char x[100][100]={0};
int i;
fp1 = fopen("quine.c","r");
for(i=0;i<50;i++)
fgets(x[i],50,fp1);
for(i=0;i<50;i++)
printf("%s",x[i]);
}




But Can we call this a Quine Program?

The answer is NO.
Why?
Because, after compilation if you change the source code, new source file will be printed. Then how do you write a quine program?

Heres an implementation of Quine:


char *s="char *s=%c%s%c;%cmain(){printf(s,34,s,34,10,10);}%c";
main() {printf(s,34,s,34,10,10);}

Interesting C Program -9

Something weird in the output of the following program:


#include "stdio.h"
void main(void)
{
int c = 10;
printf("%d\n",c);
printf("%d\n",sizeof(++c));
printf("%d\n",c);
}

The output will be:
10
4
10
++c inside sizeof function is ignored.
Why?


The answer goes like this:
The input argument to sizeof function is datatype and not data. So the datatype of ++i will be considered instead of data ++i. So it will not be incremented.

Interesting C Program -8

Just C the potential of the space in the following C Program:
(Try removing the space before %c in scanf)

#include
int main()
{
char c;
scanf("%c",&c);
printf("%c\n",c);

scanf(" %c",&c);
printf("%c\n",c);

return 0;
}


Interesting C Program -7

Guess the Output of the following C Program:


#include "stdio.h"
int main()
{
int i=43;
printf("%d\n",printf("%d",printf("%d",i)));
return 0;
}


The answer is 4321.
Explanation:
printf returns the number of letters printed.

Interesting C Program -6

One more Interesting Program

#include "stdio.h"
#include "stdlib.h"
#define DPRINTF(x) printf("%s:%d\n",#x,x)
int main()
{
int Y=5;
DPRINTF(Y);
system("pause");
}


Interesting C Program -5

Guess the output of the following C program!!!
If your guess is 40, it is definitely not!!!

#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;
}

Explanation:
The input to the function is not the entire array. Only the address of the first element of the array will be passed into the function.

Interesting C Program -4

A Program that counts the number of bits set in a number:


#include "stdio.h"
#include "stdlib.h"
int Count_Bits(int a)
{
int i=0;
int b[10]={0,0,0,0,0,0,0,0,0,0};
int c=0;
while(a!=0)
{
b[i] = a%2;
a = a/2;
i++;
}
for(i=0;i<10;i++)
{
c+=b[i];
}

return c;
}
int main()
{
int x,y;
printf("ENTER A VALUE LESS THAN 1023:");
scanf("%d",&y);
x=Count_Bits(y);
printf("%d",x);
system("pause");
}

The following is another excellent implementation of the same program:

int CountBits(unsigned int x)
{
int count=0;
while(x)
{
count++;
x = x&(x-1);
}
return count;
}


Interesting C Program -3

Can you write a C program to print the String in the center of the Screen...
Heres a little demonstration of that.

/*
This program will move the string to the center of the screen.
Center in this context is a relative thing. So I have taken my screen size as 80
and did the program. The user has to change according to his size of the screen.
*/
#include"stdio.h"
#include"stdlib.h"
#include"string.h"
void mystring(char* s);
int main()
{
char name[10];
mystring("ENTER YOUR NAME\n");
mystring("");
scanf("%s",&name);
mystring(name);
mystring("\n");
system("pause");
}
void mystring(char* s)
{
int screen_size = 80;
int l=strlen(s);
int pos=(int)((screen_size-l)/2);
for(int i=0;i < pos;i++ )
printf(" ");
printf("%s",s);
}



Interesting C Program -2

I thought the following program was a perfect C program. But on compiling, I found a silly mistake. Can you find it out (without compiling the program :-) ?

#include "stdio.h"
#include "stdlib.h"

void 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;
}


The bug is in "OS_HP-UX_print();". The function should not use '-' symbol. It will be considered as a minus. So the compiler will show error as OS_HP has not yet been defined and UX_print has not yet been defined.
Try the following code. The correct version.

#include "stdio.h"
#include "stdlib.h"

void 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;
}


Interesting C Program -1

The expected output of the following C program is to print the elements in the array. But when actually run, it doesn't do so.

#include"stdio.h"
#include"stdlib.h"
#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]);
system("pause");
return 0;
}

The culprit is the initialization in the for loop. The initial value should be a positive integer.

Try this program. This program will do the intended task.

#include "stdio.h"
#include "stdlib.h"
#define TOTAL_ELEMENTS (sizeof(array)/sizeof(array[0]))
int array[] = {1,2,3,4,5};
int main()
{
unsigned int d;
for(d=0;d {
printf("%d",array[d]);
system("pause");

}
system("pause");
return 0;
}



A Contribution from Mr. SasiKumar:

The code can be replaced as follows:

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

int main()
{
int d;
for(d=-1;d < = (signed)(TOTAL_ELEMENTS-2);d++)
printf("%d\n",array[d+1]);
system("pause");
return 0;
}