Pointer In C (In Depth) (Final) Part 4

Generic Pointer in C Programming

Generic pointer:

void pointer in c is known as generic pointer. Literal meaning of generic pointer is a pointer which can point type of data.

Example:

void *ptr;

Here ptr is generic pointer.

Pointer in C (In Depth) Part 3

Pointer to function in c programming

What will be output if you will execute following code?

int * function();

void main(){

auto int *x;

int *(*ptr)();

ptr=&function;

x=(*ptr)();

printf("%d",*x);

}

int *function(){

static int a=10;

return &a;

}

Output: 10

Explanation: Here function is function whose parameter is void data type and return type is pointer to int data type.

x=(*ptr)()

=> x=(*&functyion)() //ptr=&function

=> x=function() //From rule *&p=p

=> x=&a

So, *x = *&a = a =10

Pointer in C (In Depth) Part 2

Arithmetic Operation with Pointer in C Programming

Rule 1:

Address + Number= Address

Address - Number= Address

Address++ = Address

Address-- = Address

++Address = Address

--Address = Address

Pointer In C (In Depth) Part 1

POINTER

Pointer is a variable just like other variables of c but only difference is unlike the other variable it stores the memory address of any other variables of c. This variable may be type of int, char, array, structure, function or any other pointers. 

For examples:

(1) Pointer p which is storing memory address of a int type variable:

int i=50;

int *p=&i;

(2) Pointer p which is storing memory address of an array:

int arr[20];

int (*p)[20]=&arr;

C Programming Question Part 3

Pattern Print with Unique and Extreme Logic

Pattern  1.	*** ** * ** ***
Code:	#include <stdio.h> main() { int i,x,j; for (i=2; i>=-2;i--) { x = 1 + 2*abs(i); for (j=1;j<=x;j++) printf("*"); printf("\n"); } }
Pattern 2.	RAJVEER A        E      J        E V        V E        J E        A REEVJAR
Code:	#include<conio.h> #include<string.h> void main() {      char str[20];       int i,j,k,len;       printf("Enter the String: ");       gets(str);       len=strlen(str);       puts(str);       printf("");       for(i=1;i<len-1;i++)       {             printf("%c",str[i]);             for(j=0;j<len-2;j++)                   printf(" ");             printf("%c\n",str[len-i-1]);       }       strrev(str);       puts(str); }
Pattern 3.	*  **    ***  ** *
Code:	#include <stdio.h> main() { int i,x,j; for (i=2; i>=-2;i--) { x = 1 + abs(i); for (j=1;j<=x;j++) printf(" "); for (j=1;j<=x;j++) printf("*"); printf("\n"); } }
Pattern 4.	1 01 101 0101
Code:	#include<stdio.h> #include<conio.h> void main() {   int i,j;   int count = 1;   clrscr();   for(i=1;i<=4;i++)   {         for(j=1;j<=i;j++)         {             printf("%d",(i+j+1)%2);                        }     printf("\n");      }   getch(); }

C Programming Questions Part 2

Find The Outputs for Questions:

---

Que 1.

int main()
{
    int x,y=2,z;
    if ( x = y%2)
         z =2;
    a=2;
    printf("%d %d ",z,x);
    return 0;
}

Output:    Garbage 0 

Explanation:

This question has some stuff for operator precedence. If the condition of if is met, then z will be initialized to 2 otherwise z will contain garbage value. But the condition of if has two operators: assignment operator and modulus operator. The precedence of modulus is higher than assignment. So y%2 is zero and it’ll be assigned to x. So the value of x becomes zero which is also the effective condition for if. And therefore, condition of if is false.

---

Que 2.

int main()
{
    int a[10];
    printf("%d",*a+1-*a+3);
    return 0;
}

Output:      4
Explanation:
From operator precedence, de-reference operator has higher priority than addition/subtraction operator. So de-reference will be applied first. Here, a is an array which is not initialized. If we use a, then it will point to the first element of the array. Therefore *a will be the first element of the array. Suppose first element of array is x, then the argument inside printf becomes as follows. It’s effective value is 4.

a + 1 – a + 3 = 4

---

Que 3.

int main()
{
    static int i=5;
    if(--i){
        main();
        printf("%d ",i);
    }  
}

Output:      0 0 0 0
Explanation:

Since i is a static variable and is stored in Data Section, all calls to main share same i.

---

Que 4.

int main()
{
    int x;
    printf("%d",scanf("%d",&x));
    /* Suppose that input value given
        for above scanf is 2 */
    return 1;
}

Output:      1
Explanation:

scanf returns the no. of inputs it has successfully read.

---

Que 5.

int main()
{
    unsigned int i=65000;
    while ( i++ != 0 );
    printf("%d",i);
    return 0;
}

Output:      1
Explanation:
It should be noticed that there’s a semi-colon in the body of while loop. So even though, nothing is done as part of while body, the control will come out of while only if while condition isn’t met. In other words, as soon as i inside the condition becomes 0, the condition will become false and while loop would be over. But also notice the post-increment operator in the condition of while. So first i will be compared with 0 and i will be incremented no matter whether condition is met or not. Since i is initialized to 65000, it will keep on incrementing till it reaches highest positive value. After that roll over happens, and the value of i becomes zero. The condition is not met, but i would be incremented i.e. to 1. Then printf will print 1.

---

C Programming Interview Question Part I

Que 1.	What is an lvalue?
Ans.	An lvalue is an expression to which a value can be assigned. The lvalue expression is located on the left side of an assignment statement, whereas an rvalue is located on the right side of an assignment statement. Each assignment statement must have an lvalue and an rvalue. The lvalue expression must reference a storable variable in memory. It cannot be a constant. For instance, the following lines show a few examples of lvalues:
	int x; int* p_int; x = 1; *p_int = 5;
	The variable x is an integer, which is a storable location in memory. Therefore, the statement x = 1 qualifies x to be an lvalue. 1 = x Here compiler generate the error because the left value is contact which cannot be assigned.
Que 2.	What is an rvalue?
Ans.	rvalue can be defined as an expression that can be assigned to an lvalue. The rvalue appears on the right side of an assignment statement. Unlike an lvalue, an rvalue can be a constant or an expression, as shown here:
	int x, y; x = 1; /* 1 is an rvalue; x is an lvalue */ y = (x + 1); /* (x + 1) is an rvalue; y is an lvalue */
	An assignment statement must have both an lvalue and an rvalue.Therefore, the following statement would not compile because it is missing an rvalue:  int x;  x = void_function_call() /* the function void_function_call() returns nothing */ If the function had returned an integer, it would be considered an rvalue because it evaluates into something that the lvalue, x, can store.
Que 3.	What are enumerations?
Ans.	They are a list of named integer-valued constants. Example:       enum color { black , orange=4,yellow, green, blue, violet }; This declaration defines the symbols “black”, “orange”, “yellow”, etc. to have the values “1,” “4,” “5,” … etc. The difference between an enumeration and a macro is that the enum actually declares a type, and therefore can be type checked.
Que 4.	What are register variables? What are the advantages of using register variables?
Ans.	If a variable is declared with a register storage class, it is known as register variable. The register variable is stored in the cpu register instead of main memory. Frequently used variables are declared as register variable as it’s access time is faster.
	For Eg. register int x=90;
Que 5.	What do you know about Storage classes?
Ans.	A storage class defines the scope (visibility) and life time of variables and/or functions within a C Program. There are following storage classes which can be used in a C Program
	auto register static extern