www.howardism.org
Babblings of an aging geek in love with the Absurd, his family, and his own hubris.... oh, and Lisp.

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…

tournament-bracket.png

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

servers-1.png

Modems

modem.jpg

Modem Connection

Computer would “call” another computer

  • Very slow
  • Had to know the computer’s number
  • Computer had to be on

servers-2.png

Do Computers Talk Directly?

Computers do connect to each other:

servers-3.png

But they don’t connect directly.

Just seems that way.

Web Invented in 1993

Computers are either:

servers-4.png

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

servers-5.png

Internet is a Cloud

servers-6.png