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Computer Literacy
Some of the contents of this are a bit dated now, but it is still a wonderful introduction.
Contents
• Part 1: The Desktop Interface
• Part 2: Data & Files
• Part 3: Hardware
• Part 4: The Internet
Part 1: The Desktop Interface
[Video Playlist]
Unit 1 - Video 1
A Personal Computer (or PC) usually comes as either a "desktop" (i.e.: with a separate tower, monitor, etc.), or as a "laptop" (i.e.: where all of it is integrated into a single portable unit).
Hardware - the physical computer and its parts
Software - a set of digital instructions to be run by the computer
Program - a piece of software
Nine Commonly Used Types of Programs:
1. Word Processor - a program for creating and editing text documents
2. Spreadsheet - a program mostly used in business for storing and processing data
3. Web Browser - a program for browsing web pages from the Internet
4. eMail Client - a program for receiving and sending email
5. Instant Messenger - a program for sending and receiving text messages in real time
6. Media Player - a program for playing media (audio and video)
7. Image Editor - a program for editing images
8. Video Editor - a program for editing video
9. Games
Operating System - program for running other programs (e.g.: Windows, GNU+Linux, Mac OS, etc.)
Unit 1 - Video 2
Most Operating Systems display programs as "windows", little boxes with three basic components:
1. A Title Bar that shows the name of the program
2. A Border that gives it a boundary that can usually be resized
3. A Content Pane that shows what the program is doing or has options to be selected
Windows can be changed in size, or overlap one another when multiple programs are running.
People interact with windows with a cursor that is directed by a mouse. What the buttons on the mouse do depends on what the cursor is hovering on. Generally:
The left mouse button selects things (to open or to focus on). To move or resize things, "click-and-drag" (i.e.: press and hold the left mouse button while moving).
The bottom of the screen usually has a Task Bar. It might display a "Start Menu" with a list of programs, buttons that represent windows that are open, etc.
The Desktop is where windows are displayed. Icons are files that can be opened.
Program windows usually have three buttons on the top right:
Minimize - hide the window; open it again by clicking its button on the Task Bar
Maximize / Demaximize - make window cover the whole Desktop or return to its previous size
Close - closing the window, stopping the program
Windows do not always represent separate programs. A Popup or Dialog is a window that is attached to the program in another window. They appear temporarily and a user must interact with them in some way for them to close.
Some programs also naturally run in several windows at once.
Unit 1 - Video 3
There are common, reoccurring design patterns for many programs (i.e.: how they appear within a window). These are called Widgets. Some common Widgets are:
• Button - click to perform the action that it represents
• Text Box - a box that one can click to type or edit text
• Drop-Down List - a menu that one can open and select options from
• Checkbox - a box that one can toggle off and on by clicking
• Radio Buttons - a set of circular buttons where only one of them can be selected at a time; similar to a Drop-Down List
• Tabs - allows the window to be split up into separate portions that are only visible when selected
• Scroll Bar w/ Scroll Pane - allows a portion of the window to "scroll" (i.e.: move up and down, or side to side) in order to hold more content
• Menu Bar - another "bar" below the Title Bar that has a set of menus for program functions
The right mouse button diplays a Context Menu, which shows options for whatever the cursor is hovering over when it is pressed. When you cannot find a feature, try right-clicking.
Double-clicking the left mouse button (i.e.: two quick presses) will usually "open" whatever the cursor is hovering over.
The Start Menu usually has:
a list of programs
a list of common locations
options which control the computer itself (shut down, restart, etc.)
"Pinned programs" will always be displayed, whereas "recent programs" are displayed by how often they are accessed. One can usually display all of them alphabetically, or search through them with a "search box".
Unit 1 - Video 4
The Keyboard Cursor is usually a blinking vertical bar.
What The Buttons On The Keyboard Do:
ESC (escape) - exit a Dialog or deselect something
F1-F12 (function keys) - their use varies from program to program
Print Screen - captures a screenshot
Scroll Lock - mostly unused
Pause/Break - mostly unused
CTRL (control) - often used in keyboard shortcuts or combinations (e.g.: CTRL-W)
ALT (alternate) - often used in "accelerators", which are shortcuts that quickly open menus
"Windows" Key - often shows the Start Menu
Context-Menu Key - show the Context Menu of the selected item
Insert - toggle text-entry mode
Delete - delete character immediately after cursor
Home - jump to the start of a line
End - jump to the end of a line
Page Up - scroll up one whole screen height
Page Down - scroll down one whole screen height
Cursor Keys or Arrow Keys - move up, down, left, right
Numpad ("Number" Pad) - faster way to enter numbers and math symbols; toggled by Num Lock button
Shift - hold to type uppercase letters and alternate symbols; also used in key combos
Caps Lock - toggles "caps lock", where any letter typed is uppercase
Tab - insert tab character (equivalent to 4-5 spaces); cycle through keyboard focus
Enter - start a new text line; push a button
Unit 1 - Video 5
The Task Bar may have buttons of programs that are not actually open.
System Tray (or "notification area") is usually off to the right. This displays icons representing programs that are running, but which the user does not interact with much.
The Clipboard is a program-independent location in memory for temporarily storing data (like text, images, files, etc.). This allows one to move data from program-to-program.
Copy - copy data to Clipboard
Paste - insert data from Clipboard into program
Cut - copy data to Clipboard while removing from program
The Clipboard only holds one thing at a time. Copy or Cut will overwrite what is already there.
Common Keyboard Shortcuts:
Cut - CTRL-X
Copy - CTRL-C
Paste - CTRL-V
Undo - CTRL-Z
Redo - CTRL-Y
Save - CTRL-S
Select All - CTRL-A
Part 2: Data & Files
[Video Playlist]
Unit 2 - Video 1
Files are organized into Folders
Bits (short for "binary digits") - are two states symbolized by 1 or 0 and that can represent:
true or false
yes or no
on or off
In order for data (like numbers and text) to be operated upon by a computer, it has to be converted into binary.
Different types of characters are associated or "mapped" to different binary numbers. This set of associations is called a Character Map. If each computer uses the same Character Map, then it makes it easier to communicate between them.
Pixels (short for "picture elements") are portions of small sections of images whose color is represented by a string of numbers. These numbers can be converted into binary, and the screen displays them to recreate the image.
Videos are simply a succession of images.
Audio is turned into numbers by converting an "analog signal" (such as a sound wave) into a "digital signal" (such as bits with two distinct states). This is called "sampling".
If we think of sound as represented as a waveform, we can measure the height of the height of the waveform at various points. This gives us a string of numbers that can be used to represent that wave.
A byte is 8 bits.
Prefixes:
kilo- thousand
mega- million
giga- billion
tera- trillion
..etc.
Don't confuse byte with bit and vice versa! This carries over to abbreviations. For example:
kb = kilobit
kB = kilobyte
Data transfer speeds are usually given in bits, while storage capacities are usually given in bytes.
Unit 2 - Video 2
Storage devices: hard drives, flash drives, optical media (CDs, DVDs, etc.)
[Whenever possible, store stuff that is updated frequently on hard drives and flash drives; store stuff that does not change much on optical media.]
File - a piece of data stored on a drive
Directory (or Folder) - a list of files and/or other directories
Drives have a hierarchy of directories.
Root Directory - the unnamed directory at the top of a drive's hierarchy
File Path - all of the directories that a file is in; they are listed in order all the way back to Root and separated by slashes
File Extension - a string of letters after the name of a file that specifies what type of file it is (e.g.: .jpg, .pdf, .mp3, etc.).
Unit 2 - Video 3
Icons on the Desktop are really files and directories. The Desktop is really just a directory that is always visible.
A File Browser allows one to look through files and directories. It usually displays them as a hierarchy.
Unit 2 - Video 4
The File Browser may allow one to change how files and directories are displayed (as a list, as icons, etc.).
Program Associations - which program is used to open a specific file type
Unit 2 - Video 5
Cut, Copy, and Paste can be used to rearrange files within directories.
Archive File - a file which contains other files and directories
Compressed Archive File - an archive file that has been compressed; a common format is .zip
Shortcut File - a file which points to another file that makes it easier to get to; usually it is denoted by a little arrow on the icon; if the File Path changes, it won't work anymore
Unit 2 - Video 6
Text Editor - edits text without formatting
Programs are made up of:
.exe (executable)
.dll (dynamic linking library) - extra code an executable can connect to
resource files - extra data used by the program (e.g.: images of icons)
configuration files - holds settings
Registry - holds configuration files
Installer - a program installs another program (uncompresses files, puts them in the proper directories, and modifies configuration files in the Registry
Uninstaller - undoes installation
Unit 2 - Video 7
As programs are updated, they are assigned version numbers.
Usually it is given by two numbers separated by a dot. The first represents major upgrades, and the second represents minor revisions.
Some programs automatically check for updates.
Software Repository - system that downloads and installs / updates software
Examples: APT (Advanced Packaging Tool), Steam, etc.
Bug = undesirable behavior of a program
When a program locks up, we can close it with the Task Manager (open with CTRL+SHIFT+ESC).
"Processes" are what are actually running on the computer.
Part 3: Hardware
[Video Playlist]
Unit 3 - Video 1
A monitor is not necessarily a computer.
A tower may have:
• A power plug
• Various video monitor or TV connections (Composite, S-Video, VGA, DVI, HDMI, etc.)
• Mic jacks (sound output and inputs)
• Ethernet (Network) connection
• USB ports
USB (Universal Serial Bus):
can supply power
"hot-pluggable" (devices can be running when connected)
"chainable" (several devices can be connected simultaneously through a "hub")
Unit 3 - Video 2
• Drive bay(s) for holding hard drives
• Power supply
• Cooling fan
• Motherboard
On motherboard:
• Expansion Slots (PCI / PCI Express)
• DIMM Slot (for RAM)
• CPU Socket
• SATA connections [IDE connections are usually used for "legacy" hard drives and CD/DVD drives.]
Video Cards, Sound Cards, and Network Cards are often built right into the motherboard now. However, Expansion Slots usually hold a Graphics Processing Unit (GPU).
RAM (Random Access Memory) is faster than other forms of storage, but volitile. It holds the code and data of running programs.
CPU (Central Processing Unit) executes program instructions, reads and writes to RAM and I/O
Unit 3 - Video 3
Booting The Computer:
1. Power on
2. CPU executes instructions in the BIOS
3. BIOS code looks for operating system
4. Operating System loads
Usually the BIOS will tell you a key to hit to enter the BIOS configuration menu; this can be used to tell it to look for an operating system in another location (i.e.: the "boot order" of drives).
One has to have an Operating System on that drive.
Driver - code that tells the Operating System how to communicate to a particular I/O device
Part 4: The Internet
[Video Playlist]
Unit 4 - Video 1
Network -
+multiple computers connected to each other
+data can be sent from any system on the network to any other
+a network is owned and controlled by a person or organization
"Host" = a computer
A "router" = a "host"
Multiple networks connected together through "routers" = an "internet"; data sent from a host on one network to another goes through a router
the Internet = all networks connected together all over the world
Internet Protocol (IP) -
+data sent in packets
+each host and router has a unique 32-bit address, an IP address
Internet Service Provider (ISP), the one who owns a network over a given area
There could be multiple paths through the networks to connect two computers together. When a packet reaches a router, it is the router that chooses what to do with it.
One can usually receive data ("download") faster than they can send data ("upload") through a network because you have to pay to send information. In this case, the ISPs pay the "backbone networks" which connect them together.
Networks physically span a specific region.
A modem is connected to ISP's network. The modem is given an IP address.
The modem should be connected to an "access router", not directly to a computer. "Access routers" allow multiple computers to use the same internet connection. Note that an "access router" is different from a "router" (in the sense that we used previously).
Unit 4 - Video 2
A network is usually defined as communication between two or more computers, but to be more specific:
• Server - a program that listens for requests and responds
• Client - a program that makes requests of other programs
DNS (Domain Name System)
+a sytem of resolving names to IP addresses (i.e.: turns number into words for easier use by humans)
+all "top-level domains" are controlled by a designated authority (e.g.: com, net, org, edu, mil, gov, uk, ca, de, etc.)
+most top-level authorities let people lease subdomains (e.g.: google.com, yahoo.com, wikipedia.org, etc.)
• DNS server - program which your computer asks to resolve domain names
DNS servers are periodically updated by connecting to the authorities of top-level domains to make sure that the association between names and IP addresses is current.
URL (Universal Resource Locator) - string of text designating location of a thing on the internet
schema://host/path
schema = nature of the thing
host = the location (IP address or a domain name)
path = the thing
Unit 4 - Video 3
"The web" is not necessarily the same as "the Internet"
[If I had to differentiate the two, I would say that "the Internet" is how the hardware communicates through IP, and "the Web" is the use of HTTP. Therefore, Gopher, Gemini, Tor, etc. would not be "the Web" because they use different protocols.]
*Web Browser - displays web pages
A web page is an HTML (Hyper-Text Markup Language) document. Web browsers retrieve HTML documents and other resources using HTTP (Hyper-Text Transfer Protocol) from web servers.
Everything on the Internet uses IP. HTTP exists inside of the context of IP. It is a protocol within a protocol.
• HTML - a document format with text, images, links, and...
• Form Widgets - text boxes, pulldown menus, buttons, etc.
Dynamically generated pages - when the server changes a web page based on user input; old pages used to be static (i.e.: unchanging)
Unit 4 - Video 4
• Search Engine - a service that indexes pages on the web
Search engines do this by "spidering the web". In other words, they follow all of the links on web pages to index them, looking at the text that they contain to categorize them. When you search for a term, it will display all of the associated web pages that have been indexed.
Since there can be literally millions of pages that cover the same topic to some extent, search results are usually ordered by popularity (i.e.: what people who use the search engine seem to search for most).
They make money by selling advertising space ("sponsored links").
• Bookmark - a URL stored in the browser
eMail is not the web!
SMTP (Simple Mail Transfer Protocol)
POP (Post Office Protocol)
IMAP (Internet Message Access Protocol)
These are protocols that allow two email servers to communicate with one another.
eMail addresses function something like URLs
Examples
Email Clients: microsoft outlook, mozilla thunderbird, etc.
Webmail: gmail, yahoo, etc.
The web and email are some of the most popular applications of the Internet, but there are others, such as:
VoIP - Voice over Internet Protocol; essentially telephone service over IP (e.g.: Skype)