Examples of Bits, Numbers and Data Representations

Binary Clock



Can you read this clock?
Hint - it displays binary numbers.
Is it getting the time from your computer's clock,
or from a web-site, or neither?

Colors


  How many different colors can be chosen here?

QR Code



   How many BITS (pixels) are there in the picture above?
   Why is this more useful than a bar-code (below)?
   More QR Code information here.

UPC Bar Codes


   How does a computer read this? 
   Does it read the digits or the bars?
   How do the bars work?  try reading this

Morse Code


    Can you read this?  Maybe read this first.

Mark Sense Sheet


Why does this require a special pencil?
Why can't you use a black pen?

Characters


What is a "character code"?
What does unicode mean?
What does hex mean?

Flashing Lights and Switches

PDP 8    Altair

Why did they use lights and switches? 
Why not use a keyboard and monitor?

Printer Control Codes

PCL5HP codes

  Why are there both HEXADECIMAL and DECIMAL codes shown?
  Can you successfully use a printer WITHOUT this chart?
  So who needs this chart?

Hex Editor

Try to guess the file type shown in each of these hex dumps:







Practice Questions

You will need a hex editor to do these exercises.

Hex viewer/editor

Here are some sample files to look at - you need to save them on a local disk drive.

    BigBlue.html  Blue BMP   BigBlueDoc.doc   flag.bmp   blueDoc.rtf

== Practice ==
Use a hex editor to do each of the following:

  1. Open an HTML file. 
    Type your name into the file and save it -
    choose an appropriate position so that your
    name appears when the file is opened in a browser.
  2. Open an RTF document.
    Type your name into the file and save it -
    choose an appropriate position so that your
    name appears when the file is opened in a browser.
  3. Open an MS-Word document.
    Type your name into the file and save it -
    choose an appropriate position so that your
    name appears when the file is opened in a browser.
  4. Open the Blue.bmp file.
    It contains only blue pixels.
    - Change the blue bytes so that the color is darker (smaller numbers).
    - Change 4 pixels to be red.
  5. Open the Flag.bmp file.
    It contains 3 different colored stripes.
    - Change the bottom pink stripe to be black.
      Look at the resulting image and check for success.
    - Change the middle stripe to be RED.
      Look at the resulting image and check for success.
  6. Find out which of the tasks above could be performed
    using Notepad instead of a hex editor.
  7. In the MS-Word document, you will see something like this:
    T.i.m.e.s. .N.e.w. .R.o.m.a.n
    Explain why there all those periods between the letters.
  8. Open an .html file in Notepad.
    Insert special characters for the Greek letters : Δ Σ ∇