/* This program demonstrates:
 * 1. Using cout to print literals, variables and text prompts for clarity
 * 2. Declaring, initializing and using variables of different primitve types
 * 3. The 3 numerical integer types - short, int and long
 * 4. Different ways of representing an integer - decimal, octal, hexadecimal
 *
 * Variables:
 * Declaring a variable is us telling C++ to make room in memory to
 * hold a value. Variables have 5 properties - name, type, size, value
 * and address.
 * The name of a variable is an identifier. Follow rules and conventions
 * for naming identifiers.
 * The identifier is just the "word" we use to refer to the value in
 * the variable. Conventionally, it makes sense in context, but it doesn't
 * have to, in order to just produce the required output.
 * Initialization is giving the variable its first value, this value may
 * change later. If we do not initialize variables, the leftover "junk"
 * value might bleed into our program and produce the wrong result.
 */
#include <iostream>
using namespace std;

int main()
{
	int num;			// declares a variable
	
	num = 10;			// initializes it - gives it the first value
	
	cout<<"num: "<< num <<endl;		// print the value stored in num
	
	/* The point of a variable is that it can change values through the
     * course of a program.
     * The following line changes the value in num from whatever it was
     * set to previously (10), to 48
     */
	 
	num = 48;
	
	cout<<"changed value of num: "<< num << endl;
	
	/* There are 3 numerical integer types - short, int and long
    * int is considered the "standard" type for numeric values without fractional
    * parts. ints occupy 4 bytes in memory.
    * shorts are smaller ints, occupying 2 byes. longs are bigger ints, occupying
    * 8 bytes.
    * All 3 of these, and char, are incapable of holding fractional parts.
    */
   int num = 1276;          // usually the default "integer" type
   short smallNum = 20000;  // For "smaller" numbers, up to 32000
   long bigNum = 546546764646465798;    // can hold up to 18 digits
   
   /* Escape sequences are certain characters, that, when preceded by the backslash
     * character, has a special meaning when printed. For example, in the folowing
     * lines, \n will print as a new line */

    cout<<"num: "<< num <<"\nsmallNum: "<<smallNum<<"\nbigNum: "<<bigNum<<endl;
	
	/* We can give values larger/smaller than the range end-points to a variable. 
	 * This will compile and run, but give us the wrong answer, since it exceeds the range */
	 
	 smallNum = 98856;
	 cout<<"smallNum is now: "<< smallNum << endl;
	 
	
    /* C++ understands 3 ways of representing integers. The usual "human-readable"
     * way is the decimal representation, which has 10 different digits 0-9
     * It is also possible to represent integers in octcal or hexadecimal systems.
     * Octal numbers only use the digits 0-7, and must be prefaced with a 0
     * Hexadecimal numbers use 16 different digits: 0-9 and the A, B, C, D, E,
     * and F to reperesent a face value of 10, 11, 12, 13, 14, and 15 at that digit
     * Hexadecimal numbers must be prefixed with 0x */

    num = 191;          //decimal
    smallNum = 031;     //octal
    bigNum = 0x48A;     // hexadecimal

    //The following line will print the decimal representation of the numbers above

    cout<<"num: "<< num <<"\nsmallNum: "<<smallNum<<"\nbigNum: "<<bigNum<<endl;

	/* We can do math and store the result in variables. For example, the next 3
     * lines assign the value 8.5 to the side length of a square and calculate its area */

    double sideLength = 8.5;
    
    double area = sideLength * sideLength;
    cout<<"The area is "<<area<<endl;
	
    return 0;
}