wpe41.gif (23084 bytes)CIS3355: Business Data Structures
Fall, 2008
 

How are characters stored?

We already know the answer, because we know:

1.  Characters are symbols and the computer does NOT work with symbols
2.  The computer ONLY works with numeric values
3.  The basic unit of storage is a byte (8-bits)
4.  Characters are stored on 8-bits according to the ASCII coding scheme

If we look at the ASCII tables, the Decimal, Octal, Hex, and Binary values for each ASCII character are all given:

Decimal Octal Hexadecimal

Binary

Symbol

Meaning
0 0 0

00000000

NUL

The NULL Character
1 1 1

00000001

SOH

start-of-heading
2 2 2

00000010

STX

start-of-text
º º º º º º º º º º º º º º º º º º
33 41 21 00100001 ! Exclamation Mark
34 42 22 00100010 " Double Quotation
35 43 23 00100011 # Number Sign
º º º º º º º º º º º º º º º º º º
48 60 30 00110000 0 The Character 0
49 61 31 00110001 1 The Character 1
50 62 32 00110010 2 The Character 2
51 63 33 00110011 3 The Character 3
52 64 34 00110100 4 The Character 4
º º º º º º º º º º º º º º º º º º
65 101 41 01000001 A Capital A
66 102 42 01000010 B Capital B
º º º º º º º º º º º º º º º º º º

 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

Reminder:

For the first test, you MUST memorize (there is no other way of doing this) the corresponding decimal values for the ASCII characters:

  1. NUL (i.e., decimal 0)

  2. BEL (i.e., decimal 7)

  3. Backspace (BS; i.e., decimal 8)

  4. Carriage Return (CR; i.e., decimal 13)

  5. Escape (ESC; i.e., decimal 27)

  6. Space (SP; i.e., decimal 32)

  7. The digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 (i.e., '0' = decimal 48; '1' = decimal 49; '2' = decimal 50 and so forth)

  8. The Upper case alphabet: A ,,, Z (i.e., 'A' = decimal 65; 'B' = decimal 66; 'C' = decimal 67 and so forth)

  9. The Lower case alphabet: a ... z (i.e., 'a' = decimal 97; 'b' = decimal 98; 'c' = decimal 99 and so forth)

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

For example, the character 'H' (Uppercase 'H') is stored as the integer 72 on 8-bits (1-byte):

Notice that since we have 8-bits to work with, we have 28 = 256 combinations, meaning we can represent, for example, all of the integers from 0 to 255.

Wait, Wait !!! That's not very many !!! How can we store larger integers ??

Just as we saw earlier, we need to add more bits.

.How many ???

Depends. We'll talk about that in the next tutorial.

Some good references to help you better understand Characters include:

ASCII: From Wikipedia
What is ASCII?
An explanation of ASCII

Some questions you should be able to answer:

1.  Which of the following statements are false?

a.  Characters are symbols and the computer works with symbols
b.  The computer ONLY works with numeric values
c.  The basic unit of storage is a byte (8-bits)
d.  Characters are stored on 8-bits according to the ASCII coding scheme
e.  Given 8-bits, we can store 256 characters

    Answer: A

2.  Show how the character 'k' (lower case 'k') would be stored


This page was last updated on 05/28/05