updated

Solutions/Q-01/CRC_ErrorDetectionAlgorithm.java

@@ -1,6 +1,6 @@
 // Contributed by - Anuj Das ( GC University, Silchar - @ Department of Computer Science )
 
-// 1. Simulate Cyclic Redundancy Check (CRC) Error Detection Algorithm for Noisy Channel.
+// 1. Simulate and implement Cyclic Redundancy Check (CRC) Error Detection Algorithm for Noisy Channel.
 
 import java.util.Scanner;
 
@@ -10,7 +10,7 @@ public static String xorOperation(String modified_message, String polynomial) {
 		int size_in_bits = 16;
 		int shift = modified_message.length() - polynomial.length();
         while(shift >= 0) {
-            modified_message = Integer.toBinaryString(Integer.parseInt(modified_message,2)^(Integer.parseInt(polynomial,2)<<shift));
+            modified_message = Integer.toBinaryString(Integer.parseInt(modified_message,2)^Integer.parseInt(polynomial,2)<<shift);
             shift = modified_message.length() - polynomial.length();
         }
 
@@ -25,8 +25,8 @@ public static String xorOperation(String modified_message, String polynomial) {
 
 // It generates the encoded data/message to be transmitted (i.e., by adding CRC Check Bits to the Original  Message)
 	public static String generateCRC_CheckBits(String modified_message, String polynomial) {			
-		String remainder = xorOperation(modified_message,polynomial);
-		remainder = remainder.substring(remainder.length() - modified_message.length());
+		String remainder = xorOperation(modified_message,polynomial);								// 16bits remainder
+		remainder = remainder.substring(remainder.length() - modified_message.length());			// substring(int startIndex)
 
         int CRC_CheckBits[] = new int[modified_message.length()];
 		for(int i = 0; i < modified_message.length(); i++) {
@@ -49,34 +49,46 @@ public static String modifyMessage(String message, String polynomial) {
 		return message;
 	}
 
+// Passing Through Noisy Channel
+	public static String noisyChannel(String msgToBeTransmitted) {
+		StringBuilder noise = new StringBuilder(msgToBeTransmitted);
+		noise.setCharAt(msgToBeTransmitted.length()/2 , '1');
+		String noisyData = noise.toString();
+		return noisyData;
+	}
+
 
 	public static void main(String[] args) {
 		Scanner sc = new Scanner(System.in);
 		System.out.print("Enter the Data(Message) to be Encrypted:  ");		// Original Message
-		String message = sc.next();		    // Test --> 1010000							
+		String message = sc.next();		    // Test --> 1010000	, 100100111				
 
 		System.out.print("Enter the CRC Generator(Polynomial):  ");			// CRC Generator 
 		String polynomial = sc.next();		// Test -->  1001	
 
+//  Sender's end
 		String modified_message = modifyMessage(message,polynomial);
 		System.out.println("Modified Data(Message):  " + modified_message);
 
 		String msgToBeTransmitted = generateCRC_CheckBits(modified_message, polynomial);
 		System.out.println("\nData(Message) is ready to be Transmitted:  " + msgToBeTransmitted);
 
-		System.out.print("Enter the Data(Message) to be Transmitted:  ");
-		String send_data = sc.next();
+//  Noisy Transmission Channel
+		String send_data = noisyChannel(msgToBeTransmitted);
+		System.out.println("Data(Message) Transmitted through Noisy Channel:  "+send_data);
+
 
+// Receiver's end
 		String checkAllZeroes = xorOperation(send_data,polynomial);
 
 // It checks if the remainder contains only zeroes  --> If it contains only zeros then the data/message is accepted else considered as error in Transmission 
 		for(int i = 0; i < checkAllZeroes.length(); i++) {
 			if(checkAllZeroes.charAt(i) == '1') {
-				System.out.println("Error in Transmission!");
+				System.out.println("\nError in Transmission!\n");
 				return;
 			}
 		}
 
-		System.out.println("No! Error in Transmission!");
+		System.out.println("\nData(Message) Transmitted Successfully!\n");
 	}
 }

Solutions/Q-06/GetLocalHostAddress.java

@@ -7,6 +7,6 @@
 class GetLocalHostAddress {
     public static void main(String[] args) throws UnknownHostException {
         InetAddress localhost = InetAddress.getLocalHost();
-        System.out.println(localhost.getHostAddress());
+        System.out.println("LocalHost Address: "+localhost.getHostAddress());
     }
 }

Solutions/Q-07/GetIPAddress.java

@@ -9,8 +9,12 @@
 class GetIPAddress {
     public static void main(String[] args) throws UnknownHostException{
        Scanner sc = new Scanner(System.in);
-       System.out.print("Enter a valid URL of Website:  ");
+       System.out.print("Enter a valid URL(including https://) of Website:  ");
        String web_url = sc.next();          // https://www.youtube.com/
+
+    //    if(web_url.charAt(0) == 'H' || web_url.charAt(0) == 'h') {   }
+    //    else { web_url = "https://" + web_url;   }
+
         try {
             InetAddress address = InetAddress.getByName(new URL(web_url).getHost());
             String ip = address.getHostAddress();