Servers and Clients
Let’s Review: HTML
What is a file?
Answer
Special document on computer that only has letters.
What makes a file a web page?
Answer
If the file ends in .html
What is a tag?
Answer
Looks like:
<tag>
How do you surround text with a tag?
Answer
<tag> Surrounded text </tag>
What is the Difference?
Between <TAG> and <tag>
Answer
Nothing.
What tag surrounds the entire web page?
Answer
<html> The whole web page goes here... </html>
What is a computer tree?
Answer
Like a tree on its side…
Answer
More like a tournament bracket…
What tag follows <HEAD>
Answer
<html> <head> Anything here is not shown! </head> <body> Stuff that is shown goes here! </body> </html>
Why do we have <HEAD>?
Answer
Magic stuff goes there…
Do all tags surround text?
Answer
Nope.
<img src="folderA/folderB/some-picture.png" />
Client and Servers
On the web, you are either a client or a server.
What does that mean?
Once upon a time…
Each computer was an island
Code was shared physically:
- Hand friend a “floppy disk”
- Type code printed in a magazine
Modems
Modem Connection
Computer would “call” another computer
- Very slow
- Had to know the computer’s number
- Computer had to be on
Do Computers Talk Directly?
Computers do connect to each other:
But they don’t connect directly.
Just seems that way.
Web Invented in 1993
Computers are either:
Every file on a server has an address.
Internet Address: URL
http://www.howard.com/pers/resume.html
Every “address” has five parts:
| Protocol | → http |
| Computer | → www |
| Domain | → howard.com |
| Folder | → pers |
| File name | → resume.html |
Internet Communication
For something like Snapchat:
- First photo is uploaded to server
- Server stores photo
- Client asks for any files
- Server gives it the photo
Internet is a Cloud
