/**********************************************************************
Programmer: Tommy Lam
Last Edit Date: 9/3/2015
Filename: TommyLamLab1-SignedInts

**********************************************************************/

#include <iostream>
using namespace std;

void decimalToBinaryConversion(int tempInteger, int SIZE, int* powersOfTwo, char* binaryConversion);

// Function to invert all the binary integers from 0 to 1 and 1 to 0
// then it will add 1
void negativeDecimalToBinary(int tempInteger, int SIZE, int* powersOfTwo, char* binaryConversion);

int main()
{
        int userInteger = 0; // Delare the integer that user will input
        int tempInteger = 0; // Declaring a temp integer to hold user's inputted integer
        int const SIZE = 16; // Declare a constant SIZE for use with array
        // Declare array to hold the converted decimal to binary
        // Most significant powers of 2 start from left to right. From 2^15 to 2^0 -- Look up table
        int powersOfTwo[SIZE] = {32768, 16384, 8192, 4096, 2048, 1024, 512, 256, 128, 64, 32, 16, 8, 4, 2, 1};
        char binaryConversion[SIZE] = {'0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0'};

		cout << "This app converts an integer from -32768 to 32767 " << endl << "into 16-bit 2's complement binary format." << endl << endl;
		cout << "Created Fall 2015 for CISP 310" << endl << "by Tommy Lam" << endl << endl;
		cout << "------------------------------------------------\n"; // break lines for user to see display easier

        cout << "Please input an integer in the proper range: ";
        cin >> userInteger; // Input statement to hold user's input into userInteger

		tempInteger = userInteger;

		if ((userInteger < -32768) || (userInteger > 32767))
		{
			cout << "Sorry, your integer is out of the range.";
		}
		else
		{
			if (userInteger < 0)
			{
				negativeDecimalToBinary(tempInteger, SIZE, powersOfTwo, binaryConversion);
			}
			else
			{
				decimalToBinaryConversion(tempInteger, SIZE, powersOfTwo, binaryConversion);
			}
		}

        cout << "------------------------------------------------\n"; // break lines for user to see display easier
        cout << endl;

        cout << userInteger << " decimal is" << endl; // Display user's chosen integer

		for(int n = 0; n < SIZE; ++n)
		{
			cout << binaryConversion[n]; // display what the binary conversion of that decimal integer is
			if ((n + 1) % 4 == 0)
			{
				cout << ' ';
			}
		}

        cout << endl << endl; // emptylines
        cout << "------------------------------------------------\n"; // break lines for user to see display easier

        system ("pause"); // leaves screen up
        return 0;
}


void decimalToBinaryConversion(int tempInteger, int SIZE, int* powersOfTwo, char* binaryConversion)
{
	 for (int n = 0; n < SIZE; ++n) // Loop to go through every element in array
     {
		 if (tempInteger >= powersOfTwo[n]) // If statement that will run in the for loop until n < 16
		 {
			 binaryConversion[n] = '1'; // Sets the char '1' if userInteger < powersOfTwo[n]
             tempInteger = tempInteger - powersOfTwo[n]; // Reduces the user integer every time a powersOfTwo is used
         }
		 else
		 {
			 binaryConversion[n] = '0'; // else set the char to '0'
		 }
     }
	 return;
}

// Function to invert all the binary integers from 0 to 1 and 1 to 0
// then it will add 1
 void negativeDecimalToBinary(int tempInteger, int SIZE, int* powersOfTwo, char* binaryConversion)
 {
	 tempInteger = -tempInteger; // changes the negative decimal integer into a positive

	 // call void decimalToBinaryConversion to convert the integer into binary
	 decimalToBinaryConversion(tempInteger, SIZE, powersOfTwo, binaryConversion);

	 // invert 0's to 1's and 1's to 0's
	 for (int n = 0; n < 16; ++n) // Loop to go through every element in array
	 {
		 if (binaryConversion[n] == '0') // if char in the array is '0', then..
		 {
			 binaryConversion[n] = '1'; // it will be set to '1'
		 }
		 else
		 {
			 binaryConversion[n] = '0'; // else it will be set to '0'
		 }
	 }
	 for (int m = SIZE - 1; m >= 0; --m)
	 {
		 if (binaryConversion[m] == '0') // if char is the same as '0'
		 {
			 binaryConversion[m] = '1'; // add the 1 to the 0
			 break; // breaks out of for loop
		 }
		 else
			 binaryConversion[m] = '0'; // else set char to '0' because 1 + 1 is 0 and we carry the 1 to the element before
	 }

	 return;
 }

 /****************************************************************************************************


 1. What are the smallest negative decimal number and largest positive decimal
number that can be stored in 16 bits using 2s complement format? Why?
- The range of values are from -32768 through 32767. This is because a 16-bit twos complement integer can only have 2^16 unique values, including zero.

2. In your HLL language of choice, what procedure or operator allows you to extract
a single character from a string?
- In C++ you can use the operator str.at or []

3. In your HLL language of choice, what procedure or operator lets you concatenate
(combine) characters into a single string?
- In C++ you can use strcat or + concatenate characters into a single string.

4. In your HLL language of choice, what procedure or operator lets you replace a
character in a string with a different character?
- In C++ you can use str.replace to replace a character in a string with a different character.

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