Wednesday, May 31, 2017

How to Trace Any IP Address

In my earlier post, I had discussed about How to find the IP address of a remote computer. After you obtain this IP address, it is necessary to trace it back to the source. So, in this post I will show you how to trace any IP addressback to its source.

How to Trace the IP Address Back to the Source?

In fact, tracing an IP address back to its location is a lot simpler than what many people imagine. There exists many online tools using which you can accomplish this job. One of my favorite site is
Just go to and enter the IP address that you want to trace in the dialog box and click on “Find Location”‘. With just a click of a button you can find the following information for any given IP address:
  • Country in which the IP is located
  • City to which the IP address belongs to
  • Latitude/Longitude of the IP’s location
  • Zip Code of the region to which the IP belongs to
  • Time Zone associated with the IP
  • Name of the ISP to which the IP address belong to
  • Internet Speed of the computer associated with the IP
  • Weather Station associated with the region of the IP
  • Domain name associated with the IP address
A sample snapshot of the results from is given below:

You can also visually trace route any IP address back to its location. For this, just visit and enter the IP you want to trace in the dialog box and hit the “Proxy Trace” button. Wait for few seconds and the visual trace route tool displays the path Internet packets traverse to reach a specified destination. Hope this helps. Please pass you comments.

How to Find the IP Address of a Remote Computer

Most of you may be curious to know how to find the IP address of your friend’s computer or the IP of the person with whom you may be chatting. If so, then this post will surely help you out.
In this post I’ll show you how to find the IP address of a remote computer in simple steps.

How to Capture the IP Address?

I have created a PHP script to make it easier for you to capture  the IP address of the any computer of your choice. Here is a step-by-step process to find out the IP address:
  1. Download the IP Finder Script (IP_Finder.ZIP) that I have created from the following link:
  2. Open a new account in X10Hosting(or any other free host that supports PHP).
  3. Extract the IP_Finder.ZIP file and upload the two files ip.php andip_log.txt into the root folder of your hosting account using the File Manager.
  4. You can rename the ip.php to any name of your choice.
  5. Set the permission to 777 onip_log.txt.
Now, you are all set to find the IP address of your friend or any remote computer of your choice. All you have to do is send the link of ip.php to your friend or the person with whom you’re chatting. Once the person click’s on the link, his/her IP address is recorded in the file ip_log.txt.
For your better understanding let’s take up the following example:
Suppose you open a new account in with the subdomain asabc, then your IP Finder link would be:
You have to send the above link to you friend via email or while chatting and ask him to visit that link. Once your friend clicks on the link, his IP address will be recorded along with the Date and Time in the ip_log.txt file. After recording the IP address, the script will redirect the person to so as to avoid any suspicion.
To find the recorded IP address, check the logs using the following link:
The sample log will be in the following format:
NOTE: You have to replace abcwith your subdomain name.
I hope this helps. Express your opinion and suggestions through comments.

How to Hack a Computer

The question “how to hack a computer”is probably the one that is most frequently asked by many Internet users and hacking enthusiasts. So, in order to address some of the common questions and doubts on the subject, I have decided to write down this article. If you are looking for information on possible ways to hack a computer, this post can surely help you out.

What Computer Hacking Really Means?

Computer hacking is a vast subject and it has several different meanings. For example, when someone superficially asks how to hack a computer, it can simply mean how to break the password of a local or remote computer so as to gain access to it. However, hacking is not only that which involves breaking into a computer. If you go deeper, computer hacking can also involve things like techniques to bypass the authentication of a system, hack Internet users, computer databases, software programs and so on.
So, to define in simple words computer hacking is a means of exploiting the weakness in a computer system or network in order to gain unauthorized access to its data or take advantage of it.

How Can I Begin to Hack?

To hack a computer, you need to do know how computers actually work and learn some basic concepts on the subject. If you are serious and passionate about it, you can take up an ethical hacking course that will help you master the skills. You can pick up a book that will teach you the concepts of computer hacking right from the basics. If you are a beginner, we recommend the book “Hacking Secrets Exposed”which is an excellent source of information to start off.
Hacking Secrets Exposed

What Skills Do I Need to Hack a computer?

Even though there exists a lot of ready-to-use tools and programs on the Internet, you should possess at least a fair amount of computer knowledge to make use of them. Things like basics of operating system, computer networks and their protocols, firewalls and knowledge of how each of these work seems necessary. If you want to take it up as a profession and want to become an ethical hacker or penetration tester you will have to go a few steps further and consider learning operating systems like Unix/Linux and also programming languages like C, PHP, JavaScript, SQL etc.
If you are completely new to hacking and only have a basic knowledge of computer, you can refer freely available resources on the Internet to develop your skills. However, if you need an easy to follow guide with all the necessary resources at one place and don’t mind spending a few dollars, go for the bookHacking Secrets Exposed which is a perfect source of learning for beginners and intermediate readers.

Is Computer Hacking Legal?

In most cases hacking a computer without the permission of its owner is considered illegal. However, there are many ethical hackers who are hired by large companies and government organizations with special permissions to break into a computer in cases such as catching a cyber criminal or terror group. Sometimes penetration testers are given prior permission to hack computers so that possible vulnerabilities could be found and patched up before another hacker exploits it. In such cases it is completely legal to hack a computer.

Learn How to Hack – Hacking Simplified

If you are a beginner and need to learn how to hack, the information provided in this post can surely help you out. For the sake of simplicity and easy understanding I have written this post in the form of question and answer with some of the frequently asked questions for beginners and enthusiasts.

How can I Learn to Hack as a Beginner?

If you are a beginner and have little or no knowledge of hacking, the best way to learn is to start from the basics. Don’t try to hack something big or attempt for something that is not easily possible. Instead try to spend time in mastering the basic concepts that forms a foundation for your further learning. To successfully learn how to hack, the following are some of the steps that you can take:

Step-1: Explore the Fundamentals

If you are new to hacking or have little knowledge of computers, you can start off by exploring the fundamental concepts such as operating system basics (Windows and Linux), computer networking, network protocols, firewalls and how each of these stuffs work etc. You can make use of resources and websites on the Internet to source your knowledge. If you are more interested in exploring any of these stuffs in detail, you can pick up a book that deals with your favorite topic in a much detailed fashion.

Step-2: Find a Good Source that will Teach How to Hack in Simple Steps

Since the information presented on websites and other free Internet resources are fragmented and do not give a holistic view of the concept, it is highly necessary to find a good source of knowledge that will teach you how to hack in a step-by-step easy to follow manner. For this I recommend the bookHacking Secrets Exposed which is a perfect source for learning how to hack.
The following are some of the reasons why I recommend this book for you:
  • With this book you will learn how to hack right from the basics in a very simple step-by-step manner.
  • The book is designed for beginners which is extremely simple and easy to follow.
  • You do not need to have any prior knowledge of hacking.
  • Get latest hacking techniques with practical examples.
  • You can easily apply the knowledge gained to hack like a pro!
Hacking Secrets Exposed

Step-3: Learn Programming

If you really want to hack like an elite hacker, programming is something that you can’t skip down. Even though there exists a lot of ready made tools and programs that let you hack with ease, it is always better to have some basic understanding of programming languages like HTML, PHP and JavsScript so that you will be in a better position to figure out how they work and what’s going on in the background. Nevertheless, one can always be a good hacker without knowing how to program at all.

How Long does it Take to Learn Hacking?

This question is hard to answer as hacking is not something that can be mastered overnight. It requires knowledge, skills, creativity, dedication and of course the time. For your hack attempts to be successful, you should adopt a hacker’s mindset and start thinking just like the hacker. Everyone can master it and hack like a pro provided they learn it from the basics and build a solid foundation.
So, to become a hacker all you need is passion to learn, perseverance and a good source of knowledge like Hacking Secrets Exposed. This book will guide you through various concepts that make you learn hacking right from the basics.

Hacking for Beginners

Are you a beginner who wants to learn hacking but don’t know where to start? If so you are at the right place. Since most of the books and free resources on the Internet are only meant for those who already have a considerable amount of knowledge on the subject, they fail to teach hacking for beginners. Therefore, I have decided to come up with this post that gives useful tips for beginners on how to kick start their journey to becoming a hacker.

What is the Best Way to Learn Hacking for Beginners?

Consider the following steps:
Step-1: Begin with the Basics
For beginners who have little or no previous knowledge of hacking, it is always better to start off from the basics. Instead of directly learning how to hack, you can begin exploring more about topics such as computer networks, network ports, firewalls,common network protocols like IP address, HTTP, FTP, DNS, SMTP etc. along with how each of those stuffs work.
You can also begin to learn more about alternate operating systems Linuxwhose knowledge becomes very much essential in the field of hacking. The more you learn about the basics, the more easy it is to find vulnerabilities and device exploits. Once you develop a basic understanding of the fundamental concepts, you will be in a position to easily understand various hacking techniques that are in practice.
Step-2: Find a Good Source to Start Learning
Hacking Secrets ExposedIf one has a fair amount of experience in the field of hacking, there exists so many books and websites that give out technical information on latest vulnerabilities along with possible ways to exploit them. However, for beginners it is hard to find sources that teach hacking right from the basics in a simple and easy to follow manner.
So, I decided to put together all my 10+ years of experience in the field and come up with a book for beginners called Hacking Secrets Exposed which demands no prior knowledge of the topic and is easy for the readers to follow and understand at every step. This book also comes packed with all the necessary fundamental concepts (as mentioned in the step-1) so that readers can find them all at one place. Therefore, I recommend this book for all those beginners who have a dream to start off their journey to becoming a hacker. 
Step-3: Learn Programming (Optional)
If you want to take your hacking skills one step ahead, programming is something that you can’t skip down. Although you can easily find a lot of ready made tools and programs that let you hack with ease, it is always better to have some basic knowledge of programming languages like PHP and JavsScript so that you will be in a position to develop your own tools and exploit codes. However, if you do not wish to learn programming you can skip this step and still be a good hacker.

How Long does it Take to Master the Skills of Hacking?

Since hacking is not something that can be mastered overnight, you should never be in a hurry to get going. It requires knowledge, skills, creativity, dedication and of course the time. Depending upon the amount of effort and dedication you put, it can take up anywhere between a few months to few years to develop all the the necessary skills. Everyone can become a hackerprovided they learn it from the basics and build a solid foundation. So, if you want to be a hacker all you need is passion to learn, a good source of knowledge that will guide you through the basics and some perseverance.

What is Ransomware and How to Stay Protected

Ransomware is a type cyber attack which uses malware to affect the files on the computer by holding them hostage so that the user has to pay a sum of amount in order to to release the affected files. Once the files falls into the trap of ransomware attack it cannot be accessed through any means unless and until it is released by the group which has caused the attack.

Who is Affected by Ransomware?

All kinds of business which are done online are affected including small scale and large scale business. Sometimes cyber criminals even target home computers just so they can get some extra money as they have poor security. Even some of the organizations will be targeted as they have vast databases and needs to be protected all the time. These organizations pay to keep their networks safe from attacks by ransomware. But those who cant afford to get security will be easily targeted.

Can Ransomware be Prevented?

Ransomware can be prevented by following some of the simple procedures:
  • First of all the data should have a backup. So if there is an attack on your data by ransomware, you can easily get the data restored and don’t have to fall for the ransom demand.
  • Another way is to keep an up to date security suite. A good security suite will prevent from almost all kinds of attack on data.
  • It is wise to keep the software and Operating System updated as it will help in prevention of any kinds of new malware attacks.
  • It will also be better if the extension of the files present in the data to have visible file extensions. By doing that we can tell if any suspicious file extension activity is present in the data.
  • It will also be helpful to avoid visiting suspicious websites and clicking on anonymous links and webpages.
  • Do not open emails sent by anonymous persons who may be trying to harm you. By staying away from such links you can help yourself stay out of trouble.

Tuesday, May 30, 2017

C Program Without a Main Function

Have you ever wondered how to write aC program without a main function? Can a C program execute with a main function? Is it possible to do that?
Well, the answer is YES! There can be aC program without a main function. Here is the source code of the program without a main function:
#include<stdio.h>  #define decode(s,t,u,m,p,e,d) m##s##u##t  #define begin decode(a,n,i,m,a,t,e)  int begin()  {  printf(" hello ");  } 
The above program runs perfectly fine even without a main function. But how? What’s the logic behind it? How can we have a C program working without a main function. Read on to find out the answer…
Here, we are using a preprocessor directive called #define with arguments to give an impression that the program runs without the main function. However, in reality it runs with a hidden main function in it.
NOTE: A Preprocessor is program which processes the source code before compilation.
The ‘##‘ operator is called the token pasting or token merging operator. That is, we can merge two or more characters with it. Now, look at the 2nd line of program:
#define decode(s,t,u,m,p,e,d) m##s##u##t
What is the preprocessor doing here? The macro decode(s,t,u,m,p,e,d) is being expanded as “msut” (The ## operator merges msu and t into msut). The logic is, when you pass (s,t,u,m,p,e,d) as argument it merges the 4th, 1st, 3rd and the 2nd characters (tokens).
Now, look at the third line of the program:
#define begin decode(a,n,i,m,a,t,e)
Here the preprocessor replaces the macro “begin” with the expansion decode(a,n,i,m,a,t,e). According to the macro definition in the previous line, the argument must be expanded so that the 4th, 1st, 3rd and the 2nd characters must be merged. In the argument (a,n,i,m,a,t,e) 4th, 1st, 3rd and the 2nd characters are ‘m’, ‘a’, ‘i’ and ‘n’.
So the third line “int begin” is replaced by “int main” by the preprocessor before the program is passed on to the compiler. That’s it.
The bottom line is that, there can never exist a C program without a main function. Here, we are just playing a gimmick that makes us believe that the program runs without the main, but there actually exists a hidden main function in the program. Here, we are using the proprocessor directive to intelligently replace the word “begin” by “main”. In simple words: int begin = int main.

How to Make a Trojan Horse

Most of you may be curious to know about how to make a Trojan or Virus on your own. Well, here is an answer to your curiosity. In this, post I’ll show youhow to make a simple trojan on your own using the C programming language.
This trojan when executed will eat up the hard disk space on the root drive (The drive on which the Windows is installed, usually C: Drive) of the computer on which it is run. Also, this trojan works pretty quickly and is capable of eating up approximately 1 GB of hard disk space for every minute it is run.
So, I’ll call this as Space Eater Trojan. Since this program is written using a high level programming language, it is often undetected by antivirus programs. The source code for this program is available for download at the end of this post. Let’s see how this trojan works:
Before I move on to explain the working of this program, you need to know what exactly is a Trojan horse and how it works. Unlike what many of us think, a trojan horse is not a virus. In simple words, it is just a program that appears to do a favorable task but in reality performs undisclosed malicious functions that allow the attacker to gain unauthorized access to the host machine or cause a damage to the computer.

Now let’s move on to the working of our Trojan:

The trojan horse which I have created appears itself as an antivirus program that scans the computer for malware programs. However, in reality it does nothing other than eating up the hard disk space on the root drive by filling it up with a huge junk file. The rate at which it fills up the hard disk space it too high. As a result, the the root drive gets filled up completely with in minutes of running this program.
Once the disk space is full, the trojan reports that the scan is complete. The victim will not be able to clean up the hard disk space using any of the cleanup program. This is because, the trojan intelligently creates a huge file in the Windows\System32 folder with the.dll extension. Since the junk file has the .dll extension it is often ignored by the disk cleanup software. Hence there is now way to recover the hard disk space other than reformatting the drive.

The algorithm of the Trojan is as follows:

  1. Search for the root drive.
  2. Navigate to the following location on the root drive.
  3. Create the file named “spceshot.dll“.
  4. Start dumping the junk data onto the above file and keep increasing its size until the drive is full.
  5. Once the drive is full, stop the process.
You can download the Trojan source code HERE. Please note that I have not included the executable for security reasons. You need to compile it to obtain the executable.

How to compile the program?

For step-by-step compilation guide, refer my post How to compile C Programs.

How to test this trojan horse?

To test the trojan, just run theSpaceEater.exe file on your computer. It will generate a warning message at the beginning. Once you accept it, the Trojan runs and eats up the hard disk space.
NOTE: To remove the warning message you’ve to edit the source code and then re-compile it.

How to fix the damage and free up the space?

To remove the damage and free up the space, just type the following in the “run” dialog box:
Now search for the file “spceshot.dll“. Just delete it and you’re done. No need to re-format the hard disk.
 NOTE: You can also change the ICON of the virus to make it look like a legitimate program. This method is described in the post: How to Change the ICON of an EXE file ?
Please pass your comments and tell me your opinion. I am just waiting for your comments. 🙂

How to Hide Your IP Address Online

eed to Hide Ip Address?
Well, Here’s a Complete Guide to Hide Your IP in Simple Steps!
Every computer on the Internet has a unique IP address allotted to it which makes it possible to trace it back to its exact location. However, there are ways to hide IP address online! In this post, I will discuss some of the popular ways to hide your IP address so that your identity and privacy are kept safe.

How to Hide Your IP?

Following are some of the most common ways to hide IP address on the Internet:

1. Using a VPN Proxy – Safe and Secure Way to Hide IP

Using a trusted VPN proxy service is by far the best way to conceal your IP address online. Here is a list of most popular VPN services that will hide your IP address:

1. Hide My Ass VPN – Hide My Ass is one of the most popular and trusted VPN service that allows people to easily conceal IP address and protect their online privacy.
2. VyprVPN – VyprVPN offers the world’s fastest VPN services that allows people to easily conceal their real IP.
Advantages of using a VPN to hide your IP address:
  1. In addition to hiding your IP, a VPN is very fast, offers high performance and encrypts all your web traffic to keep you safe from hackers and intruders.
  2. You have a long list of countries and states to select your desired IP address location.
  3. By selecting an IP address of your choice, a VPN allows you to easily access restricted websites that are not available for your country.

Why Hide IP Address?

Following are some of the reasons why people want to hide their IP address:
  1. By hiding the IP address, one can browse anonymously.
  2. To access or unblock websitesthat are not available to the IP address of a particular Geo location.
  3. To stay safe from hackers by showing a fake IP to the outside world while keeping real IP concealed.
  4. Hiding IP means hiding Geo location.
  5. Hiding IP prevents leaving a digital footprint.

2. Web Based Proxies

This is another popular way to quickly hide IP address on the Internet. Following are some of the popular web based proxies to conceal your IP address:
The downside of using these free web based proxy servers to mask your IP address is that most of them are overloaded and are too slow to use. In addition, your security and privacy may get compromised during the usage.

What is the Best Way to Hide IP Address?

I have made a sincere attempt to present you with all available options to hide your IP address. If you only want to conceal your IP address for a specific amount of time and are not concerned with the security and performance, go for the free web based proxy services.
On the other hand, if you have the necessity to hide IP address on a regular basis, need high security and performance, go for paid VPN services like Hide My Ass or VyprVPN.

How to Ensure Your IP Change?

To make sure your IP is changed, just type ‘my IP address’ on Google before and after using any of the above services. Just compare both the IP addresses and make sure they are different. If yes, that means you have successfully changed your IP so that your real IP address is hidden from public.

How to Unblock Websites in Quick Time

Learn how to unblock websites in quick time with just a few simple steps. Here is a complete guide to unblock and access any website.
Some of your favorite websites may be blocked by your school or company for reasons such as saving the bandwidth or improving productivity during work hours. Sometimes a government or ISP may suddenly block websites to impose Internet censorship resulting in real pain and inconvenience for the users. If you are an individual facing such inconvenience and want to unblock websites to bypass restrictions this article can help you out.

Ways to Unblock Websites

There exists several ways to unblock websites where some are easy and some are difficult to implement. Also, there are many obsolete methods that will not work in the present day scenario. Therefore, I am presenting only those methods that I have tested and found to be working as listed below:

1. Using a VPN Proxy – The Best Way

Using a VPN proxy is one of the easiest and best method to unblock any website in quick time. It is fast, secure and extremely reliable during all times of usage. Since it acts as an intermediary between your computer and the websites you browse your real identity such as location and IP address remain obscured to the outside world. Some of the popular VPN proxies are listed below:

1. Hide My Ass VPN – Hide My Ass is one of the most popular VPN service for unblocking any website with ease.
2. VyprVPN – VyprVPN offers the world’s fastest VPN services backed by 30-day money back guarantee.

How VPN Work?

VPN proxies will hide your IP address by replacing it with a new IP that is tied to a different physical location from where the restricted website is available. In other words, if a website you are trying to access is not available from your network or country, a VPN proxy will assign you an IP from a different country thereby unblocking the website for you.
You can select your origin to be from any country of your choice so that you can easily bypass restrictive censorship and unblock websites with ease.

2. Using Web Based Proxies

Web based proxies can be handy for users looking for a simple and free solution to unblock websites. As most of these are available for free you need not pay for them to use. However, this advantage comes with a catch: many of these free services are slow, user privacy and security is questionable and users do not have a wide range of choice to select their desired IP location.
The following are some of the web based proxy sites that you can try:

3. Using a Translator Service

Translator services such as Google Translator and Microsoft Translator can help you unblock your desired websites. These services act similar to proxy sites wherein they fetch the target site from within their own sites and display them on your screen.
In our case Microsoft Translator is more easy to use and suitable for unblocking websites. All you need to do is just visit the Microsoft Translator and type in the URL of the target site you want to unblock in the left text box. Select ‘English’ as your target language and click on Translate. This should unblock the restricted website and load it from within the Microsoft Translator’s website.

Thursday, May 25, 2017

A Virus Program to Disable USB Ports

In this post, I will show how to create a simple virus that disables the USB portson the computer (PC). As usual, I am using my favorite C programming language to create this virus. Anyone with a basic knowledge of C language should be able to understand the working of this virus program.
Once this virus is executed it will immediately disable all the USB ports on the computer. As a result you’ll will not be able to use your pen drive or any other USB peripheral devices on the computer. The source code for this virus is available for download. You can test this virus on your own computer without any worries since I have also given a program to re-enable all the USB ports.
  1. Download the source code of the virus program on to your computer from the following link:
    The download contains the following 2 files:
    • block_usb.c (source code)
    • unblock_usb.c (source code)
  2. You need to compile them before you can run it. A step-by-step procedure to compile C programs is given in my post
  3. 3. Upon compilation of block_usb.c you get block_usb.exe which is a simple virus that will block (disable) all the USB ports on the computer upon execution (double click)
  4. To test this virus, just run theblock_usb.exe file and insert a USB pen drive (thumb drive). Now you can see that your pen drive will never get detected. To re-enable the USB ports just run theunblock_usb.exe  (you need to compile unblock_usb.c) file. Now insert the pen drive and it should get detected
4.You can also change the icon of this file to make it look like a legitimate program. 

How it Works?

The idea behind the working of this virus is pretty straightforward. It works by gaining access to the Windows registry and modifying its settings to disable the USB device support on the computer.

On the other hand, the other program will re-set the registry settings back to the normal so that the support for USB devices is re-enabled. I hope you like this post. Please pass your comments.

How to Compile C Programs

In many of my previous posts especially in the Programming section, I have used C as the programming language for writing the programs. If you’re new to C programming and find it difficult tocompile the C source codes then this post is for you.
Here is a step-by-step procedure to install Borland C++ compiler 5.5 on your PC and compile the C programs.

How to Install Borland C++ compiler?

Follow the below steps to install Borland C++ compiler 5.5 on your PC:
  1. Download Borland C++ compiler 5.5 (for Windows platform) from the following link:
  2. After you download, run the fileC++5.51.exe. The default installation path would be:

How to configure Borland C++ compiler?

Here is a step-by-step instruction on how to configure the compiler:
  1. After you install Borland C++ compier, create two new Text Documents.
  2. Open the first New Text Document.txt file and add the following two lines into it:
    Save changes and close the file. Now rename the file from New Text Document.txt to bcc32.cfg.
  3. Open the second New Text Document (2).txt file and add the following line into it:
    Save changes and close the file. Rename the file from New Text Document (2).txt to ilink32.cfg.
  4. Now copy the two files bcc32.cfgand ilink32.cfg, navigate toC:\Borland\BCC55\Bin and paste them..      

How to Compile the C Source Code (.C files)?

Here is a detailed instruction on how to compile C source codes:
  1. You need to place the .C (example.c) file to be compiled in the following location:
  2. C:\Borland\BCC55\Bin
  3. Now go to the command prompt(Start->Run->type cmd->Enter)
  4. Make the following path as the present working directory (use theCD command):
  5. C:\Borland\BCC55\Bin
  6. To compile the file (example.c) use the following command:
  7. bcc32 example.c
  8. Now if there exists no error in the source code, you’ll get a compiled executable module (example.exe) in the same location (C:\Borland\BCC55\Bin).
  9. Now you have successfully compiled the source code into an executable file(.exe file).
NOTE: The above tutorial assumes that you’ve installed the compiler onto the C: drive (by default).

C Program to Print its Own Source Code

Ever wondered how to write a  C program to print its own source code ? Well, here is the source code of a C program that when executed w...