LECTURE
OCTOBER 20 2004

ASSIGNMENTS
10/22 CodeLab 7

TEST CASES

What?
- *error case*
- *normal case*
- *end case*
Example?
- skydiving, when to pull the parachute?

CHARACTERS

What?
- data type
How?
- char

What?
- literal
How?
- surround the character with single quotes, e.g. 'A'

What?
- character data type declaration
How?
- char <name> = '<literal>';

What?
- internal representation on a computer
How?
- combination of 1s and 0s

Why?
- so people can exchange data easily
What?
- ASCII
  - American Standard Code for Information Interchange
  - widely used character coding scheme
  - not all characters are printable
  - sufficient for common English, but not for many other languages
How?
- see table in book on page 517
- 128 total characters
  - requires 7 bits for representation
  - 1 byte is actually used
  - 128 leftover codes are generally used for manufacturer-specific non-standard symbols

Why?
- 256 characters not enough for foreign languages
What?
- Unicode
  - full name is Unicode Worldwise Character Standard
  - established by the Unicode Consortium
How?
- 34,168 distinct characters
- 2 bytes per character
- same as ASCII codes where overlap

What?
- Java characters
How?
- Unicode

What?
- using Unicode for Java IO
How?
- Operating System and development tool must also support

What?
- converting between integer ASCII/Unicode encodings and Java characters
How?
- to get the numerical encoding, cast a char to an int
- to get a char, cast an int to a char (but the int must be within the encoded range)

What?
- comparing characters
How?
- like numbers
- returns comparison of ASCII encoding
- letters sort alphabetically
- capital letters sort before lower case