C Interview Questions – Set 03

A pointer is a variable that refers to the address of a value. It makes the code optimized and makes the performance fast. Whenever a variable is declared inside a program, then the system allocates some memory to a variable. The memory contains some address number. The variables that hold this address number is known as the pointer variable.

The new line escape sequence is represented by “n”. It inserts a new line on the output screen.

• In case of static memory allocation, memory is allocated at compile time, and memory can’t be increased while executing the program. It is used in the array.
• The lifetime of a variable in static memory is the lifetime of a program.
• The static memory is allocated using static keyword.
• The static memory is implemented using stacks or heap.
• The pointer is required to access the variable present in the static memory.
• The static memory is faster than dynamic memory.
• In static memory, more memory space is required to store the variable.

Yes, by holding the base address of array into a pointer, we can access the array using a pointer.

#include
#include
void main()
{
int n,i,m=0,flag=0; //declaration of variables.
clrscr(); //It clears the screen.
printf(“Enter the number to check prime:”);
scanf(“%d”,&n);
m=n/2;
for(i=2;i<=m;i++)
{
if(n%i==0)
{
printf(“Number is not prime”);
flag=1;
break; //break keyword used to terminate from the loop.
}
}
if(flag==0)
printf(“Number is prime”);
getch(); //It reads a character from the keyword.
}

Yes, we can compile, but it can’t be executed.

Accessing array elements: Pointers are used in traversing through an array of integers and strings. The string is an array of characters which is terminated by a null character ‘’.
Dynamic memory allocation: Pointers are used in allocation and deallocation of memory during the execution of a program.
Call by Reference: The pointers are used to pass a reference of a variable to other function.
Data Structures like a tree, graph, linked list, etc.: The pointers are used to construct different data structures like tree, graph, linked list, etc.

printf(): The printf() function is used to print the integer, character, float and string values on to the screen.

Following are the format specifier:

• %d: It is a format specifier used to print an integer value.
• %s: It is a format specifier used to print a string.
• %c: It is a format specifier used to display a character value.
• %f: It is a format specifier used to display a floating point value.
  scanf(): The scanf() function is used to take input from the user.

Brain Kernighan.

• In case of dynamic memory allocation, memory is allocated at runtime and memory can be increased while executing the program. It is used in the linked list.
• The malloc() or calloc() function is required to allocate the memory at the runtime.
• An allocation or deallocation of memory is done at the execution time of a program.
• No dynamic pointers are required to access the memory.
• The dynamic memory is implemented using data segments.
• Less memory space is required to store the variable.