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Compsci notes

HTML - Hypertext Markup Language
You need to save and HTML file with the file ending .html or .htm (Ex: TestFile.html)
Tag - A tag is an HTML command that tells the browser to perform an action. It look likes: </a>
or <b>
Start tags have a slash in front of the command right after the first bracket (Ex: </a>)
End tags have no slash in front of the command and look like this (Ex: <a>)
An end tag cannot function with no start tag and vise versa
Attribute - Most tags contain attributes and attribute values which should further define what the
browser does.
<a href=”http://www.google.com”>search here</a>
Strict and Transitional are the most commonly used doctypes
Each element are only used once per page
Header tags are used to indicate things and their level of importance (Ex: <h1>, <h2>)
The body taghouses the main components if a web page
Bgcolor can be used to set the color of a webpage using hex color codes
Blue #0000FF
Green #008000
Red #FF0000
Blue 0, 0, 255
Green 0, 128, 0
Red 255, 0, 0
<ul> unordered list
<ol> ordered list
<li> list item
A computer is an electronic machine that executes commands and task stored in its memory.
Computer are usually fast and accurate, but they still require someone or something to tell them
what to do.
Many programming languages are used to create programs.
Some languages are further from binary than others and offer higher levels of abstraction.
Scratch is a language with higher levels of abstraction than c or assembly.
C and assembly operate a very low level and can interact directly with hardware.
Processor Unit:
The processor unti consist of two primary components: the CPU and the RAM. Both are
attacked to the motherboard. The motherboard. Also contains a bus, a set of electrical
connections, which is allows the cpu and ram to communicate with each other and all input and
output devices
CPU is a single integrated circuit also called a chip
The CPU or chip uses gates and transistors to manipulate bits. Chips gates, and transistors are
all level computer parts.
Commands and such sent to the CPU are sent in binary.
Lots of boolean logic is required for the CPU to make decisions based on binary received.
Boolean logic uses, “and”, “or
, and “and” not to check with things should be completed.
A binary number is a group of 1s and zeroes that are represented inside the computer as a
sequence of on and off signals in electric current.
Binary numbers are powers of 2 or base numbers of 2. We use base 10 numbers in every day
Beginning value is 0
(Previous value*2) + binary number
pictures , sounds and commands must be converted into binary before they can be processed
to the cpu
Memory is the place in a computer where memory is stored while being tested or changed.
Memory consist of RAM or cache. Both are temporary and will lose all memory when the
computer is turned off.
The BUS, the circulatory located on the motherboard, connects the CPU, memory, and all other
parts together
Permanent storage remains active when the computer is on or off.
Hard drives and solid state drives are permanent storage devices.
Output devices are devices that display information.
Hardware consist of all the physical components that make up the computer some examples of
hardware are the CPU, hard drive, memory, video card, network card, and monitor.
Hardware components can be low level items like chips, transistors and gates.
High level hardware components are video cards and network cards.
Multiple levels of abstraction using low-level components like gates, transistors, and chips are
used to build high-level hardware components like video cards or network cards.
A LAN is a local area network, consisting of devices that are all linked together by cable or wifi.
Typically, the devices are all in a general area.
k, usually consisting of two networks connected via satellite or cable. Unlike LAN, WANs c
A WAN is a wide area network that only shares software resources.
The internet is a collection of networks or a network of networks
The 1st computer was created by Charles Babbage; it was called the “analytical engine”.
Babbage was the first to envision a machine controlled by commands stored in its memory.
The first computer programmer was Augusta Ada Byron, the daughter of Lord Gordon Byron, a
famous English poet. She worked with the Babbage in the 19th century.
John Von Neuman was a mathematician who worked on one of the earliest computers and
developed the concept of storing programs in memory. Most modern CPUs are designed based
on his work.
Your home router has an external IP address which allows it to connect Internet
Your home router allocates internal IP addresses to all devices connected in your house that
need Internet access.
Home network: a home network is a group of devices typically connected to a devices typically
connected to a wired or wireless router
You should have a key on your home router so that random people cannot connect.
Typically, you must enter a security key to connect to your router first.
Once connected to your home router, your device will receive an IP address.
Ther router is the device that helps allocate IP addresses to all the devices you connect.
Anit-virus software and firewalls can help keep your personal information secure on your home
IPv4 addresses are 32 bit
IPv6 addresses are 128 bit
Long story short, IPv6 has much more space to use to create new IPs.
32 bits can be used to store 2^32 different values
0 to 4,294,867,295 base 10 FFFFFFFF hex - base 16
Given the following IPv4 address
This IP address consists of 4, 8 bit values.
Each section of IPv4 address is an 8 bit binary value. Each section can range from 0 to 255.
DNS is used to convert internet addresses into IP addresses.
www.apluscompsci.com is converted to
Encryption is a security system that strives to ensure that only the desired target can read the
Encryption does not prevent the message from being intercepted.
Secure Sockets Layers (SSL) provide an encrypted connection between the web server and
Most browsers show a warning if a site does not use SSL.
SSL sends all data encrypted.
Encryption is commonly used to protect info being sent across the internet
This includes emails, text messages, and login info.
Browsers can store info about where users go when on the internet.
Blogs, discussion groups, and social network are used broadcast and post information.
5695 / 5 = 1139
1139 / 5 = 227 .8 X 5 = 4
227 / 5 = 45.4 .4 X 5 = 2
45 / 5 = 1.8 .8 X 5 = 4
1 / 5 = .2 X 5 = 10
1111 base 2 to base 9
(1 X 8) + (1 X 4) + (2 X 1) + 1 =
15 / 9 = 1 667 X 9 = 6
1 / 9 = 111 / 9 = 1