G-Facts from geeksforgeeks

In C language, sizeof( ) is an operator. Though it looks like a function, it is an unary operator.

To know the IP address(es) of a URL/website, nslookup can be used at the shell/command prompt (cmd.exe). It works on both types of operating systems i.e. Linux/Windows.

In C, function parameters are always passed by value. Pass-by-reference is simulated in C by explicitly passing pointer values.
In ISO C, you can define main either to take no arguments, or to take two arguments that represent the command line arguments to the program, like this:

int main (int argc, char *argv[])
Other platform-dependent formats are also allowed by the C and C++ standards; for example, Unix (though not POSIX.1) and Microsoft Visual C++ have a third argument giving the program’s environment, otherwise accessible through getenv in stdlib.h:

Bootstrapping (compilers)
http://en.wikipedia.org/wiki/Bootstrapping_(compilers)
In computer science, bootstrapping is the process of writing a compiler (or assembler) in the target programming language which it is intended to compile. Applying this technique leads to a self-hosting compiler.
Many compilers for many programming languages are bootstrapped, including compilers for BASIC, ALGOL, C, Pascal, PL/I, Factor, Haskell, Modula-2, Oberon, OCaml, Common Lisp, Scheme, Java, Python, Scala, Nimrod, Eiffel, and more.

“Pointer arithmetic and array indexing [that] are equivalent in C, pointers and arrays are different” – Wayne Throop

G-Fact 8
To uniquely construct a Binary Tree, Inorder together with either Postorder or Preorder must be given (See this for details). However, either Postorder or Preorder traversal is sufficient to uniquely construct a Binary Search Tree. To construct Binary Search tree, we can get Inorder traversal by sorting the given Preorder or Postorder traversal. So we have the required two traversals and can construct the Binary Search Tree.

The number of structurally different Binary Trees with n nodes is Catalan number Cn = (2n)!/(n+1)!*n!
http://mathworld.wolfram.com/BinaryTree.html
The number of binary trees with n nodes are 1, 2, 5, 14, 42, ... (Sloane's A000108), which are the Catalan number C_n.

Enumeration constants (enum values) are always of type int in C, whereas they are distinct types in C++ and may have size different from that of int.

In C, struct keyword must be used for declaring structure variables, but it is optional in C++.
struct node {
   int x;
   node *next; // Error in C, struct must be there. Works in C++
};

Predict the output of following program.

#include <stdio.h>
int main()
{
   int x = 012;
   printf("%d",  x);
   getchar();
   return 0;
}
The program prints 10. Putting a 0 before an integer constant makes it an octal number and putting 0x (or 0X) makes it a hexadecimal number. It is easy to put a 0 by accident, or as a habit. The mistake is very common with beginners.

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