Both allocates memory from heap area/dynamic memory. By default calloc fills the allocated memory with 0’s

It’s a pointer variable which can hold the address of another pointer variable. It de-refers twice to point to the data held by the designated pointer variable. Eg: int x = 5, *p=&x, **q=&p; Therefore ‘x’ can be accessed by **q.

Portability – Platform independent language. Modularity – Possibility to break down large programs into small modules. Flexibility – The possibility to a programmer to control the language. Speed – C comes with support for system programming and hence it is compiling and executes with high speed when compared with other high-level languages. Extensibility – Possibility to add new features by the programmer.

NULL is used to indicate that the pointer doesn’t point to a valid location. Ideally, we should initialize pointers as NULL if we don’t know their value at the time of declaration. Also, we should make a pointer NULL when memory pointed by it is deallocated in the middle of a program.

1. To get address of a variable 2. For achieving pass by reference in C: Pointers allow different functions to share and modify their local variables. 3. To pass large structures so that complete copy of the structure can be avoided. 4. To implement “linked” data structures like linked lists and binary trees.

#include <stdio.h> int main(void) { if (printf("Hello World")) { } }  

Scope of a variable is the part of the program where the variable may directly be accessible. In C, all identifiers are lexically (or statically) scoped.

auto, register, static, extern

Declaration of a variable/function simply declares that the variable/function exists somewhere in the program but the memory is not allocated for them. But the declaration of a variable/function serves an important role. And that is the type of the variable/function. Therefore, when a variable is declared, the program knows the data type of that variable. In case of function declaration, the program knows what are the arguments to that functions, their data types, the order of arguments and the return type of the function. So that’s all about declaration. Coming to the definition, when we define a variable/function, apart from…