Computer science

There are also system files. These files there need to be properly protected from accidental deletion by a novice user. More experienced user needs to know that system files are critical files, and these need not be deleted. There are different types of file systems that help to manage files on disks. These are NTFS for Windows systems, HFS (letter H in this word stands for Hierarchical) for Mac OS, new Mac computers use Apple File System (APFS). Linux OS has many file system types. I will not be listing all of them, I will only specify a few popular choices. These are EXT4, XFS, Btrfs. YouTube video

It is possible to outline four main activities for which an operating system will be responsible for. These are: File and disk management. An operating system needs to organize data in a disk in a way that it is easily accessible. At the same time this data needs to be properly secured, so that only those users that need, can access the data. Process management. An operating system need to allow for reliable process management. It should be able to manage applications and services. Memory management. System's memory need to be properly allocated for programs and data files. Device management. An operating system needs to make device available for use. For example a sound card need to be useable, it needs to make system sounds when needed, and allow a user to manage the sounds. YouTube video

There are three main types of operating systems that majority people are using for their desktop systems. These are Windows OS, Apple OS, various flavors of Linux. Less popular operating systems are Free BSD and Open BSD. YouTube video

Common simple data types in programming are: Boolean, integer, long, float, double, char and string. Each one of these data types will use specific amount of operating system memory in a computer. Boolean data type contains values of True or False, 1 or 0. It takes only one byte. One byte is one of the smallest amount of memory, it consist of 8 bits, representing sequence of 0s and 1s. integer data type represent whole negative and positive numbers, long data type is another data type that represents whole numbers, but the range of long data type is larger than range of integer data type. Float and double a data types that represent numbers with floating point, precision of double data type is greater than precision of float data type. Car data type will only hold a single character. String data type is a collection of characters. Each data type represent different amount of memory that can be allocated, depending on their byte size. I had listed here basic data types, more complex dat...

Rubber duck debugging is a debugging technique to say out loud things which are needed to be performed. By saying things out loud it helps to find issues in the code that can be missed by just looking at the code. YouTube video

One of the most simple debugging techniques is to print out information from the code using print function to screen. More advanced techniques will include this output to a log file, by doing so the output in the screen will not be polluted by the debug output, but all the debug output will go the a log file. Making debug output going to a log file is a good programming technique. Debugging will slow down execution of this program, so before this program is released to production, most if not all debugging code needs to be removed. Debugging code is mostly for software developers to troubleshoot potential issues. More advanced debugging can be done with debugging tools. Debugging software allows line by line execution of the code, and it possible to set breakpoints, or points where the execution of the code will be paused, so line by line execution of the code can be performed. Debugging tools will also show variable values. In debugging tools it is possible to execute the rest of the ...

Debugging is a process of finding issues in the code. Computer code can be very complex and debugging can be a very tedious process. With experience a person makes less mistakes, if time had passed by, but this person still writes buggy code, than something is wrong. Term "bug" or computer bug was originated, when actual bug was found in one of the early computers, that was causing incorrect computing operations. YouTube video

Decompiling code is an opposite process to compiling code, however by doing decompiling variable names and function names will be lost. Without having proper names it will be difficult to understand what that code does. YouTube video

When source code is compiled into machine code it goes though four steps. These steps are:  Preprocessing - preprocessing in coding means to add dependencies to your code. The code that is written may rely on functionality that is available in some other code. Of course it is possible to write that code by yourself, but it will be inefficient than to use code that had been already written. It is likely that this code had been already well tested by others and don't contain many errors. Preprocessing means to use that library. Preprocessing step does not include code to your code, but simply points that this library is needed. Compiling - is the next step in the process of compiling source, this code is not yet transformed into machine code, but it is transformed to instructions that this machine can understand. This code looks like assembly code, or low level programming instructions. Before high level programming languages were developed, people used to make computer programs in t...

Intermediate code requires a use of additional software to be executed. Advantage of doing so, is that additional software will abstract use of that operating system specific functions, so that the code that had been written will not be specific to just one platform. Example of intermediate library is .NET. Even so the code that will be executed within .NET environment will not be as efficient as code that had been written specifically for that environment, however it will be abstracted enough, that operating system specific functionality will be replaced with executing methods within that environment. That environment will be responsible to use that operating system specific methods in order to perform desired functionality.

Compiled code is the code that had been transformed in machine readable format. Operating system in that machine will dictate what format of executable code needs to be. Different operating systems will have a different format of executable code, for example it is not possible to take an executable code that was compiled for Windows and run it it Apple OS because that binary will not be compatible with that system.

Computer code exceptions happen when an invalid operation is performed. For example division by 0 is done, or opening of non-existing file is performed. Typically these type of errors will cause an application to crash and exit the execution of the code that follows the line where that exception occurred. To handle exceptions it is possible to wrap the code, where an exception is expected to occur in exception handling block. In Python programming language it is try and except block. If exception occurs in try block than there are chances that it will be handled by the except block. I am saying that there are chances, because exceptions can be of different types, and it depends what type of exceptions are handled by the application. It is also possible to specify default exception handling. Default exception handling will handle all error types. YouTube video

Analog signal is a continuous signal. I am going to use an example of voice for this example. Voice of a singer in a concert is an analog voice, but MP3 file with the same song is in digital format. Analog signal in this example a voice, is a continuous change of the data. Digital form of the same song is transforming analog signal to data that can be easily stored by a computer. Higher the number or the bitrate, better the quality of that recording is going to be. The same principal applies to video as well. It is impossible to perform this operation in opposite way, take digital format and convert it to analog, because digital format has less information than analog. Example of data in analog format are vinyl disks. Music quality there is much better than in CDs, or MP3s but vinyl disks are less portable. YouTube video

Integer overflow happens when a decimal number is larger than a binary number can represent. For example 255 is represented by eight ones. If a larger number than 255 needs to be represented, then more binary places are needed. If a decimal number will is larger than a binary number can support, than value of a decimal number higher than a binary number can support will be lost. Where does it happen in practice? 32 bit systems had a limitation of about 4 billion. 4 Gigabytes of operating memory was the highest number than can be addressed by these systems. Going over 4 Gigabytes required use of more than 32 bits. That is where 64 bit processor came in action. 64 bit processors can overcome the limit of 4 gigabytes of RAM and have a much larger number of it. YouTube video

There are patterns in binary numbers. Each odd number will be represented by a binary number that ends with one, and the opposite is true too, an even number will be represented in binary format by a number that ends with 0.

Converting a decimal number to binary format involves calculation of power of two in sequential order and subtracting that value from original number, For example, if a decimal number 47 needs to be converted to binary format, then first it is necessary to list powers of two. These will be 64, 32, 16, 8, 4, 2, 1. I use small number therefore I did not use the full 8 bits for a binary number, First we need to compare power of 2 in the first position with the original number. In our case 64 will be compared with 47. 64 is larger then 47, therefore 0 will be in that place, and we can move to the next position. Next position is 32. 32 can fit into 47, therefore we will put one in that place. Next step is to subtract 32 from 47. Difference of these 2 numbers is going to be 15. We will continue doing this operation until the resulting number is going to be equal to 0. If the resulting number will become 0 before the end of binary sequence, then we can assign 0s to the rest of the positions. ...

​Computer hardware are physical parts of a computer, computer software are the files in the computer.

​Finding a specific string in the output can be done using grep and egrep commands. grep command will search for a specific string, egrep will perform regular expressions match. These commands often combined with cat command to see if specific text exists in that file.

​Similar to head functionality can be achieved with tail command. It will output last ten lines of that file by default, however number of lines to be displayed can be changed to a different value. It is possible to specify -f option to monitor that file for changes and output those changes to the screen.

​Beginning of a file can be output to standard output using head command. By default this command will only output first ten lines of a file, however this behavior can be overridden by specifying -n option with a numerical value that follows it to specify number of lines that need to be outputted using head command.

​Removing a directory in Linux can be done using rmdir command. If the directory that is ment for deletion is not empty then that directory will not be deleted. This will prevent a non-empty directory to be deleted. Before such directory can be deleted, the content of that directory needs to be deleted first.

​A file can be deleted in Linux using rm command. By default rm command will not delete directories. Directories can be deleted by specifying -r (recursive) option. If a file is write protected, then rm command will prompt a user before deleting such file. This prompt can be suppressed by specifying -f option. -f stands for force.

​A file can be moved in Linux using mv command. This command can also be used to rename a file.

​A file can be copied to a new location using cp command. If destination file already exists, then that file will be replaced.

​A new directory can be created in Linux (BSD flavors, Mac OS) using mkdir command. If that directory already exists then content of that directory will not be erased.

​touch command in Linux can be used to create a new file. If this file doesn’t exist, then a new file will be created. If file already exists then creation and modification dates of that file will be updated, but the content of that file will be intact.

​cat command in Linux can be used to output content of a file in standard output which is usually a screen. This output can be reduced with using grep or egrep commands, so only lines of text that match search condition will be displayed. This reduced output can be redirected to a file for further processing.

​It is possible to redirect output of one command to another command in a command line interface. There are couple of options there. Single > sign will replace existing content of a file with new content. For example if file contains a list of files retrieved by ls command, that this list will be replaced if listing of a directory is done, and it is redirected to that file. Appending data will not replace existing content, but it will add new content to the end existing content.

​Piping in Linux means executing another command after the first command executed and passing output first command to second one. For example it is possible to combine ls and grep commands. First command will list all the files, second command will limit this output to only content that matches search pattern.

​There are two special characters that can be used in Linux (BSD, Mac OS) terminal as wildcards. These characters are useful while listing files using terminal. These characters are ? and *. Question mark is used to replace one single character, where * is used to replace any number of characters. For example when a filename is only partially known, then it possible to use one of these characters to list many files that match search condition.

​whereis command can be used to identify which program is being used. whereis command will output full path of a program.

​Help for the commands can be shown in two ways. First one is specifying —help after a command name. Second one is typing “man” command followed by a command for which you want to get additional information. man command output is generally more descriptive than output of —help.

​A directory content can be displayed with ls command. ls is short for list. ls command will accept various command options in order to adjust the representation of that information.

​It is possible to change current working directory with cd command. cd stands for change directory. It is possible to specify full or relative path of directory. Full path will be the location of that directory in from the starting location, which is / (forward slash) in Linux. Relative path is location of that directory from the current location of the user. Going back a directory level can be specified with .. (two dots). It is possible to specify more than one double dot. Each double dot needs to be separated by forward slash symbol.  In this case a user will go back as many levels as many double dots symbols are specified.

​I will list a few common Linux commands: pwd - it stands for “print working directory”, this command will report current location of where a user is located. whoami - is a command that will report what is the current system user that is being used. This command is useful to return to use regular user instead of root user. I know this list can be expanded, and I think that I will do it later.

​I will list and I will give brief explanation of common Linux directories. Beginning of Linux file system starts with forward slash symbol. All other directories and files reside in this directory. /root is a home directory of a root user.  /etc directory contains configuration files for different applications. /home directory is the location of user files. Each user in this system will get a separate directory. Each user home directory permissions allow only that specific user to access content of that directory. /mnt is a directory where other media is mounted. /media is a directory where other media is mounted and accessible in this system. For example a flash drive will be mounted here. /bin is a location of executable files. It can be compared with “Program Files” folder in Windows. /lib this folder is the location of shared or library files. These files are similar to DLLs in Windows OS root user is able to access and edit content of these folders, however it is good idea to...

​Linux file system is different from Windows file system in a way that it doesn’t have letter activation for drives. Beginning of Linux file system is marked with / (a slash) symbol. I cover physical structure of the file system separately, this is only explanation of logical functionality of this file system.

​Terminal application is a computer application to display non-graphical information. Transmitting text uses less bandwidth than transmitting graphics.

​Linux shell is an interpreter for executing commands. There are different flavors of Linux shell. Popular shells are Bash (Borne Again Shell), C and Z shells.

​A script is not a full blown application, but a small code that does a specific task. There are couple of advantages of using a script over performing a task manually. 1. The task will be executed more reliably. 2. A task will be executed faster. There are times when scripts should not be created, but a task needs to be done manually. These are events that will happen just once or rarely. Time that is spent creating a script needs to be less than time performing this task manually. A script has a potential to create a lot of damage, because it will do things quickly. A script needs to be verified that it does things properly.

There may be a time when conversion from a binary number to a decimal number is needed. In order to convert a binary number to a decimal number each position in a decimal number can be represented by two to the power of that position place minus one. Counting in computers start with 0. For example a binary number 1001 can be represented as decimal number 9. It is 2 to the power of 3, plus 0 to the power of 2, plus zero to the power of 1, plus  2 to the power of 0. It results in 8 + 0 + 0 + 1 or 9. YouTube video

​DIV and SPAN HTML tags can be used to identify block of text that already has line breaks in it. DIV tag is a block level element, meaning it can be on its own within an HTML document. SPAN element is inline, it needs to be included in other HTML tags.

​HTML ids and classes. Ids are unique within the HTML document, they can be used to identify HTML elements. Classes are not unique, they can be used more than once. Ids and classes can be used within CSS documents to specify how specific HTML elements need to look like. Ids can be used within JavaScript code to perform specific actions to that HTML element.

​Line breaks and spaces are ignored within HTML document if they are not as part of text to be displayed.

​There are six levels of HTML headings. An HTML heading is represented by H symbol with a number that follows it. Each following HTML heading is smaller in size than a previous level. H1 heading is the largest and it needs to be used only once in a web page. It is a good idea to use lower font size, or higher numerical value of heading within the lower heading number.

​HEAD tag will have metadata about this HTML document. For example it may contain title of this web page.

​Indentation within HTML documents does not impact how this HTML file will be represented, however indentation is helpful to edit an HTML document.

​Doctype directive species which version of HTML is needed to be used when HTML document is rendered.

​It possible to use tools like Figma or Gimp to create images. I am not a graphic designer so I just recommend what can be used, but a graphic design person may have his or her favorite image editing tools. You may leave comments with your favorite graphics design tools.

​There are specific editor applications that are designed specifically to edit HTML code, These editors have syntax highlighting which is a good thing to have when editing of HTML code is done. It is possible to use Visual Studio Code or Sublime Text editor to edit HTML documents.

​HTML comments may help with understanding of specific block is there. HTML comments start with /* symbols and end with */ symbols. HTML comments may span several lines. HTML comments will not be visible in the web page, but they can add clarity of why specific block of HTML code is there.

​Having HTML style guide is a good idea, it will make web site consistently looking.

​Often source image files contain more information than exported versions of files to be used in a web site. Often source files contain information such as layers, exported image files to be used in HTML pages do not contain this information. If images need to be adjusted in a future, then it is a good idea to keep raw source files.

​Default HTML document is index.html file, in older systems that only supported three letter filename extensions, you may see HTM file extension.

​it is a good practice to lower case file and folder names used to build HTML web site. Case matters because some operating systems are case sensitive, and this web site may not work in another hosting provider.

​Space bar is disallowed symbol in HTML file names. It can be faked using dashes or underscores.

HTML stands for Hyper-Text Markup Language. HTML is the language of the Internet. HTML language is not dynamic, it is static. However dynamics can be added to web pages using JavaScript. JavaScript is a programming language for the web. HTML is rich. It can contain images, forms, links to other documents. HTML consists of tags, attributes and elements. Tags are surrounded by left and right angle brackets. Many of the tags have both opening and closing tag. For example paragraph tag will have tag indicating where paragraph starts and it will have closing tag indicating where this paragraph ends. End HTML tag contains forward slash. HTML attributes specify extra information about this element. HTML attributes are included in the opening HTML tag. It is a good practice to wrap attribute values in double quotation marks. HTML element is both a tag and content within that tag. HTML elements have parent/child relationship. HTML element that includes another HTML element is referred as a pare...

Android development can be done differently. Google had released their Android Development Studio to make Android projects, or it possible to do Android development using IntelliJ. IntelliJ is a development environment to do Java development in Windows. I hope that I will cover Android Development Studio next. Programming or coding is a difficult skill, but I will try to teach you of how to develop an Android application. IntelliJ can be obtained from the website of its manufacturer - JetBrains There are different versions of the software free and paid version. I will cover free version. Once the software is downloaded, it is necessary to install it. When IntelliJ is installed, you will be presented with options to start a new project, open a project, or clone repository. First two options are self explanatory and the third option will open a window to open a project saved in the existing code repository.

A docking station for a laptop expands laptop capability by adding additional ports to a laptop, and make this laptop act as a desktop computer. YouTube video

A computer webcam is a device to capture video. Computer web cams can be used in video conferencing. Laptop computers usually have built-in camera, so a separate web cam is needed only for desktop computers, or laptops, that don't have a web camera. Standalone web cams offer better picture quality, than built-in laptop cameras, however for video conferencing built-in laptop cameras are sufficient. YouTube video

Computer speakers are used to produce a computer sound. Sounds can be produced by the operating system, also known as system sounds, or audio can be generated by music you play, a computer game or a video. Basic configuration of speakers include left and right speakers. Speakers can also be used to generate surround sound. A subwoofer can be used to play low frequency sounds. Laptop computers usually come with built-in speakers. YouTube video

A headset is used to produce sound and capture audio. Headsets can be wired or wireless. Bluetooth is usually used in wireless headsets because Bluetooth offers low power consumption. YouTube video

A stylus is input device for touch sensitive displays or drawing pads. A stylus offers greater precision than doing the same operation with a finger. A stylus can be passive or active. Active stylus have batteries in it. Active styluses are usually pressure sensitive. YouTube video

​If you don’t like AI (Artificial Intelligence) t there is a way to remove Copilot from a Windows computer. Copilot is Microsoft’s version of AI assistant. https://mashable.com/article/copilot-windows-11-how-to-remove

​A critical vulnerability was found in Chrome browser and an attack exploding this vulnerability was used. It recommended to update Chrome web browser to fix this issue. https://www.forbes.com/sites/zakdoffman/2025/11/19/attacks-confirmed-google-issues-emergency-update-for-2-billion-chrome-users/

​An interesting story about mobile phones was published in Android Police web site. It shows that a value of iPhone is more than of an Android device. https://www.androidpolice.com/thieves-are-hilariously-turning-down-android-devices/

Wi-Fi hotspot is an ability of smartphones to share their Internet connectivity via Wi-Fi connection. Please be aware that Wi-Fi hotspot connectivity via smartphone can be disabled by the wireless service provider. Wi-Fi hotspot connectivity can also be provided by portable hotspot devises. YouTube video

Tethering is a term used to describe a condition when Internet connectivity is shared by one device with other devices. Tethering may be done via USB cable, Bluetooth, or Wi-Fi connection. YouTube video   

Bluetooth is a short range wireless communication. Devices like headphones, keyboards, computer mice may have Bluetooth communication enabled. Smart watches rely on Bluetooth connectivity. Data exchange may also happen via Bluetooth. Bluetooth requires low power, therefore devices that use Bluetooth may last a long time. There are different versions of Bluetooth. Common versions are 4.0 and 5.0. 5.0 version of Bluetooth is a low power version. Bluetooth communication is secure. Bluetooth connection in many cases requires verification of a code upon first time connection is established. YouTube video

NFC stands for Near Field Communication. It is low power and low range communication type. Communication range of NFC is about 4 centimeters. NFC is used in mobile wallets. NFC does not require manual configuration and it uses minimum power. YouTube video

Lightning connector is a proprietary type of connector that was wade by Apple. Lightning connector is used in iPhones, iPads and iPods. Lighting connector is reversable. Apple transitions to use USB-C, however it is possible to find lightning connector in many of older Apple's devices. YouTube video

Micro USB and mini USB were used before USB-C became standard. Some of the older devices may have this type of USB connector. USB is used to connect external devices of many types. YouTube video

USB-C is a modern connection type. It can be used for data and video transfer. YouTube video

External devices can be connected to a computer via USB. USB stand for Universal Serial Bus. USB devices are hot pluggable, and often the operating system already has a device driver for these. To disconnect an external USB device is often needed to "eject" from the system, or in other word disable all communications to it. USB plugs and ports can be of a different type, so please make sure that you are getting a USB device that is compatible with your system.

A faulty microphone in a laptop computer may result in no sound or muffled sound. An easy solution to a faulty microphone problem is to get an external microphone or a headeset.

Majority of mobile devices now days include front and back cameras. Replacing a camera in a mobile device or a laptop is is a difficult task. Majority of laptops may get a standalone web camera instead.

Laptop's Wi-Fi antenna may go around the screen behind the display, it is a time consuming and tedious task to replace it. The components that cover this antenna are delicate and easily breakable, so extra caution needs to be paid when this antenna is replaced. Symptoms of bad antenna may include failure to detect or to connect to a wireless network. 

Some of laptops come with an NFC adaptor. NFC stands for Near Field Communication. NFC is low power, low distance communication module. In phones NFC can be used to make payments, in laptops NFC module maybe located in obscure location. Please consult the service manual before replacing one in order to know the proper location of one. After physical installation is complete, there maybe a need to install drivers for this module.

Some of the laptops come with a fingerprint scanner. It can be used to authenticate user instead of the password. If this fingerprint scanner goes bad, it can be replaced with an another one, please pay attention to cabling when this module is replaced. Fingerprint scanners are usually more reliable than other laptop's components.

It is possible to replace wireless card in a laptop. A laptop may have couple of wires connected to the wireless card. These wires are very fragile and extra care needs to be provided to handle these. Wireless cards are usually secured with a screw, so you will need a tool to unscrew and screw the new one. A new wireless card may not be recognized by your operating system, in this case it is needed to install wireless drivers that came with that card, Please be aware that new drivers may be available from that card manufacturer, and it may be needed to install new version of the drivers. That Wi-Fi card may be operational even with the old driver, but the driver may include new functionality or bug fixes.

A drive is the main storage for the laptop. It contains files for that laptop. Usually a laptop has only one main drive. Laptop hard drives can be of two types, they can be in a form of spinnable media, or they can be in a form of SSD. SSD stands for Solid State Disk, and it has no moving parts. SSD drive takes less space, than spinnable drive. SSD drives can be also replaced, however it may be a challenge to locate one in a laptop. Please be aware that the new disk will not contain OS, if this is the only drive in your system, then you may get a message that "No bootable media is found" after the drive is replaced. Fresh installation of the operating system may need to be done, or an image of the old drive may need to be saved and restored to the new media, before that drive will become bootable.

When replacing memory module of a laptop, please ensure that this laptop is turned off and external power source is disconnected. Laptop's memory modules are smaller in size than desktop's counterparts. There could be more than one slot for the laptop memory, it is necessary to look carefully for them. Home use laptops may have just a single memory slot, however laptops that are meant for engendering work may have memory slots located in different places. Laptop's memory needs to be installed at 45 degree angle, before it can be pushed down to ensure good latch. With all kind of memory, desktop or laptop memory, please ensure good connection before locking memory. If not inserted properly, desktop memory will not be recognized, and it is possible to damage laptop memory, if extra force applied to a memory chip that was not inserted properly. When extra memory is added, please ensure that new memory is recognized by this system. Some laptops have RAM modules soldered to moth...

Laptops have smaller form factor than desktop computers, therefore laptop components are also smaller. For example memory module of a laptop is smaller than in a desktop computer. Video card is often integrated in laptop's motherboard. Desktop computer functionality can be expanded with the use of expansion cards. A laptop computer does not have expansion slots. Functionality of a laptop can be expanded with the use of USB devices.

Laptops are more fragile than desktop computers. When working with a laptop it is necessary to pay extra attention as the same actions that can be performed with a desktop computer may damage a laptop. Timewise it also may take longer to replace parts in a laptop than in a desktop computer.

Computer components can be damaged by difference of electricity between the computer you work on, and the body. In order to make charge the same between this computer and your body a wrist wrap needs to be used. A wrist wrap is made of conductive material. One end of this wrist wrap is worn on the hand and another part is attached to the computer case. The part that is worn by a human looks like a bracelet, that bracelet is connected by a wire to tweezers, and the tweezers are connected to the computer case's metal part. Antistatic mat can be used as well.

Safety is important when you are working with computer hardware.  It is important that there is no power going to that device. The device needs to be not just turned off, but physically that device needs to be unplugged.

​SFTP protocol defines how to transmit a file using SSH connection.

​Giga is a definite of about 1 billion. To be exact Giga represents 2 to the 30th power.

​In programming a function is way to separate a piece of code separately so it can be executed over and over again. A function has only one return value, but it may accept multiple values. For example finding a minimum value of two values will accept two values to compare, but will return only a single value, in this example it will be a minimum value of two values.

​FQDN is full name of the domain. In a browser FQDN is what type when we want to visit a specific website. In the network FQDN is a full name of the host.

​FTPS protocol adds encryption to the FTP protocol. Encryption is done using SSL, which is a pretty good encryption.

​FTP is a data transfer protocol. FTP uses TCP ports 20 and 21 for data transmission and authentication. Communication in FTP is not encrypted therefore it is possible to sniff network traffic and obtain username and password that used to connect to an FTP server, it is also possible to know which data is saved to FTP server, or obtained from it. Secure methods of communication include FTPS and SFTP. FTP protocol is obsolete nowadays it had been replaced with more secure alternatives. I don’t know if FTP protocol is still in use today. Maybe some legacy systems rely on FTP data transfer.

​Freeware is software that is distributed for free with no license fees .

​root user in Linux like system is a high privilege user. This user can do almost anything in that system. For example root user can install software or perform this system reconfiguration. It is a bad idea to use root user for daily operations because if root account is compromised, then an attacker can have great control over that system. Temporary access to root account needs to be used. Temporary access is done with sudo command. Permissions needs to be given to a user to execute sudo command.

​Home directory is a default location of user’s files and folders. Default location of home directories in Linux are in /home directory. Each user will get a subfolder in that folder.

​A directory is the location of files and other directories. You maybe familiar with the term “folder” in Widows OS. A directory has the same meaning and same functionality as a folder in Windows OS.

​File names in Linux are case sensitive. Filename with a word “Document” is different from a filename “document”. This case sensitivity applies to folder names too.

​Binary is a term for non-human readable format of a file. Binary executable files are platform specific. Linux will have its binaries, so will Mac OS, Windows OS and BSD. Binary files are more optimized for use by applications. Binary files will have much richer information about content of a file. For example text file will have just a text, but rich text document with that text will contain information of how big that text will be, that text location in the page, and alignment of that text to other elements. Of course it is not full description of features, but it should give a good representation of what can be done.

​Linux has great future. Linux OS has great popularity among users, and it has good support from people who support it or add new features. Android is based on Linux and iOS has roots in Unix OS.

​Majority of hacking tools are written for Linux. Linux is opened source and offers great control of how applications will behave. Even so it is possible to customize how each application will look like in Windows OS, Linux allows a person to do much greater customization.

​The word granular means changeable. All of the things in Linux can be adjusted. Of course a person that does it needs to have sufficient skills and knowledge to modify source code. Source code of an application can be very complex.

​Linux is transparent meaning that nothing is hidden a person that use Linux can know everything about implementation and such a person can modify it per his or her liking. Of course that person needs to have knowledge to understand what was done and how to modify it, because modifying source code is not a trivial task.

​Many of Linux applications use open source licenses. An open source license means that the source code of the application is available. It means that this application can be customized per your liking. Modifying a source code is not a trivial task. A person who changes source code need to have skills to do it, and such a person needs to have knowledge of doing it.

​Linux offers customization, it offer great control over how a system is going to behave. Of course it is possible to make Windows or MacOS look differently using background or theme, but Linux offers much greater customization for internal things, for example it is possible to customize how networking will behave.

​Espionage is way to determine secrets that a company or a country has.

​A vulnerability scan is a scan of a device or number of devices in order to see which issues are present. The issues may include vulnerable applications or misconfiguration of these. Please be aware that vulnerability scan results are only good for that particular scan, a new scan may include additional tests. Therefore vulnerability scans need to be performed periodically.

​Ethical hacking also known as “white-hat” hacking is a way to determine which issues a system has in order to fix these issues.

​Term RAID stands for Redundant Array of Independent Disks. RAID means that more than one drive will be used. I will try to explain common RAID levels. Common RAID levels are 0, 1, 5. More advanced RAID levels are 10 and 50. RAID level 0 is striping, when data is written or read from two drives. RAID 0 does not provide any redundancy. It is used to increase write and read performance. If one of drivers in RAID 0 fails then data in second drive will be unavailable as well. RAID 1 is called mirroring. The data which is written in one drive is duplicated to another one. RAID 1 does not provide any performance improvements for write operations, however it can improve read operations. RAID 5 is good for redundancy. Drives are configured this way that data which is written there is written to all drives. Data is split, so only a portion of data is written to each drive. RAID level 5 requires at minimum three drivers to operate. Two drives will be used for data and one for parity. RAID 10 is ...

RAM stands for Random Access Memory. Over the years there were a number of types of computer memory. First type that that I will discos is a DIMM. A type of DIMM memory that I will explain is SDRAM. S in its name stand for synchronous. Speed of that RAM was tied to speed of motherboard. Certain motherboards required specific speed of memory.  RAM can be of a different capacity and speed. Please verify of what type of capacity and speed your motherboard can support before buying more memory.

​Foreign key is the database term that defines a relationship between two database tables.The data in a table that references primary table cannot be changed or added without corresponding data existing in primary table.

​A flatbed scanner is a peripheral that allows scanning of documents. There may be several types of scanners. There could be flatbed scanners or scanners that feed through documents. Usually scanners that are flatbed usually have better resolution or quantity of scanning documents.

​Firmware is low level software that allows hardware to operate. Firmware can be upgraded to resolve issues that are found with that hardware.

​A firewall is a physical device or software that can restrict traffic between networks.

​File system is the format of how files and folders are saved on a disk. A file system can use such features as user permissions, encryption or compression. File system also specifies top limit of size of a partition that uses that file system.

​A file server is a server that contains files. These files can be used by other computers which are called client.

​File format is tightly related to file extension. File format shows how this file can be used and what type of data it contains.

​A fiber-optic cable uses light to transmit signals. Fiber optic transmissions are fast, but fiber optic cables are fragile.  Cost wise fiber-optic cables cost more per foot than network cables that use copper. Installation wise cost to install fiber an optic cable is also more than installation of a copper cable.

​EXT3 and EXT4 are common types of file systems used in Linux operating systems. EXT4 file system adds journaling to the EXT3 file system. Journaling is a way to record activities that were performed.

​EULA or End User License Agreement  is the software agreement that a user should agree to before using the software. Usually EULA is displayed to user during installation process. A user is then asked if that user agrees to it or not. If that user does agree to the terms of EILA than software installation process is cancelled.