Lesson Objectives Explain the use of binary codes to represent characters Explain the term...
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Lesson Objectives Explain the use of binary codes to represent characters Explain the term “Character set” Describe with examples (for examples ASCII and
Lesson Objectives Explain the use of binary codes to represent
characters Explain the term Character set Describe with examples
(for examples ASCII and Unicode) the relationship between the
number of bits per character in a character set and the number of
characters which can be represented.
Slide 2
Lesson Outcomes All students will identify different character
sets MOST students will score at least 4/6 on the exam questions
SOME students will attempt the extension activity
Slide 3
When you type a letter on your keyboard, for example the letter
"K," have you ever wondered what has to happen in order to display
the letter on your screen? When you type a "K," the "K" button
sends a special electrical signal consisting of 0's and 1's to the
CPU of the computer. The letter is encoded in binary. In order to
display the letter you just typed on the screen, the computer must
decode the binary to determine that the letter is a "K" and then
must display the image of a letter "K."
Slide 4
Look at the keyboard in front of you How many different
characters/letters/symbols are you able to type on your keyboard?
Dont forget upper case! You should be able to find around 100. How
many BITS would we need to represent this number of characters?
1286432168421 1111111 We need 7 bits. 1111111 = 127
Slide 5
Representing Characters Computers can only work with binary
data. Binary data can easily represent numbers. If we make each
number represent a letter, or character, then we can store
characters. One common code (ASCII) uses seven bits to store each
character.
Slide 6
ASCII ASCII = American Standard Code for Information
Interchange In total 127 codes (95 printable, 32 non-printable)
plus the null character 00000000 used as a control character but
with no associated symbol.
Slide 7
This is just part of the ASCII table
Slide 8
MISS LEVITT in denary is 109 105 115 115 108 101 118 105 116
116 MISS LEVITT in binary is 01101101 01101001 01110011 00100000
01101100 01100101 01110110 01101001 01110100 Work out your names in
DENARY and BINARY
Slide 9
Write a coded message Use the ASCII table to write a coded
message to a friend. Use the DECIMIL/DENARY conversion to write
your message Swap with a friend and de- code it!
Slide 10
What if we need more characters? 128 characters are not enough
to encode all languages. There are other systems that use more than
7 bits. EBCDIC is the Extended Binary Coded Decimal Interchange
Code this is used in IBM mainframes. It uses 8 bits so can encode
256 different characters.
Slide 11
Unicode is more common these days. Unicode comes in different
variants, but can encode more than 107,000 characters, covering 90
languages. For example, ) Unicode is a 16 bit system (2 x 8 bits)
E.g 01011011 11101101
Slide 12
What you need to know 1.These ways of representing letters and
characters are knows as Character sets 2.Two of the most common
Character sets are Unicode and ASCII 3.The number of characters
which need to be represented effects the number of bits required.
1.ASCII 7 bits for less than 127 characters. 2.EBCDIC or Extended
ASCII 8 bits for 256 characters 3.Unicode 16 bits for over 65,00
characters
Slide 13
Explain how ASCII is used to represent text in a computer
system [3] There are 3 marks therefore 3 points must be made. You
could include Each character is given a numeric code This code is
stored in binary Each character takes up 7 bits The binary code is
then translated in the CPU Some codes are reserved for characters
and keyboard shortcuts
Slide 14
State what is meant by the term character set [1] For one mark
a simple definition is needed A character set is all the characters
which have to be recognised by the computer system.
Slide 15
Unicode is also used to represent text in a computer system.
Explain the difference between the character set of Unicode and
ASCII [2] You need to directly compare two contrasting features of
Unicode and ASCII Eg. ACCII has 7 or 8 bits per character whereas
Unicode uses 16 bits OR ASCII can represent only 127 characters
whereas Unicode has a much larger character set (around
50,000)
Slide 16
Scores: C - 3/6 on the exam questions B - 4/6 on the exam
questions A/A* 5+ on the exam questions
Slide 17
Extension Correct the teacher identify the errors in the
passage of text.