c faqs

Question: Difference between arrays and pointers?
 Answer: Pointers are used to manipulate data using the address. Pointers use * operator to access the data pointed to by them
 Arrays use subscripted variables to access and manipulate data. Array variables can be equivalently written using pointer expression.

Question: What is the purpose of realloc ( )?
 Answer: The function realloc (ptr,n) uses two arguments. The first argument ptr is a pointer to a block of memory for which the size is to be altered. The second argument n specifies the
new size. The size may be increased or decreased. If n is greater than the old size and if sufficient space is not available subsequent to the old region, the function realloc ( )
may create a new region and all the old data are moved to the new region.

Question: What is static memory allocation and dynamic memory allocation?
Answer: Static memory allocation: The compiler allocates the required memory space for a declared variable. By using the address of operator, the reserved address is obtained and this address may be assigned to a pointer variable. Since most of the declared variable has static memory, this way of assigning pointer value to a pointer variable is known as static memory allocation. Memory is assigned during compilation time.

Dynamic memory allocation: It uses functions such as malloc ( ) or calloc ( ) to get memory dynamically. If these functions are used to get memory dynamically and the values returned by these functions are assigned to pointer variables, such assignments are known as dynamic memory allocation. Memory is assigned during run time.

Question: How are pointer variables initialized?
Answer: Pointer variable are initialized by one of the following two ways
              Ø Static memory allocation
              Ø Dynamic memory allocation

Question: What is a pointer variable?
Answer: A pointer variable is a variable that may contain the address of another variable or any valid address in the memory.

Question: What is a pointer value and address?
Answer: A pointer value is a data object that refers to a memory location. Each memory location is numbered in the memory. The number attached to a memory location is called the address of the location.

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