1. ASCII and Unicode

2. ASCII Inside a computer, EVERYTHING is a number – that includes music, sound, and text. In the early days of computers, every manufacturer had their own code for characters (HP, IBM, Sperry, Digital) The users didn’t care as long as they pressed A on the keyboard and got A on the screen

3. As time passed More computers meant more data and more users People wanted to share or buy or sell data from colleagues The incompatibilities in the character codes made a problem Eventually everyone decided that a “standard code” was needed

4. ASCII Several codes were considered but ASCII won! American Standard Code for Information Interchange The beginnings of the Internet in the 70’s also gave impetus to the desire for a standard code so that email clients didn’t have to know a dozen different codes just to read email from different machines across the Net

5. ASCII So what? Why do I care? Mostly, you don’t. If you press A on the keyboard and get an A on the screen, what does the code matter? ASCII is efficient, known by almost every device, easy to transmit and receive Has codes for A-Z, a-z, 0-9, space, punctuation marks and a few control codes 256 different codes (1 character fits into 1 byte of data)

6. Time passes The world starts using computers and not just countries who use the “Roman” alphabet First response: learn English But eventually the realization came that a new code that was bigger was needed Around 2000 Unicode was released “Universal Code” Has over 64K different codes

7. Unicode Covers all human alphabets and has room for more! Includes ASCII as first 256 codes A Unicode character takes TWICE as much space (at least!) as an ASCII character (2 bytes) Now in development for 4 bytes! Becoming the default code for many applications Several programming languages adding a type for “fat” or “wide” characters = Unicode!

8. Unicode Note: Unicode is NOT a “translator program” What it does do is allow you (if you know a foreign language) to write the foreign words properly spelled with the correct characters They will get transmitted correctly The recipient still has to know how to read them, but at least the words will be correctly spelled

9. Comparing strings Easy to test for equality –has to be exact match, spaces, case, length What does it mean to say one string is greater than another (or less than)? Comparison made by looking at the ASCII codes of the characters in the strings

10. ASCII – order you need to know Upper case letters all in alphabetical order ‘A’ < ‘B’ < ‘C’ < ‘D’ < … < ‘Y’ < ‘Z’ Lower case letters all in alphabetical order too ‘a’ < ‘b’ < ‘c’ < ‘d’ < … < ‘y’ < ‘z’ How do the two alphabets relate to each other? Lowercase letters are higher (greater) (after) the uppercase letters

11. More on order ‘A’ < … < ‘Z’ < … < ‘a’ < … < ‘z’ Where do the digits fit in there? ‘0’ < ‘1’ < ‘2’ < ‘3’ < … < ‘8’ < ‘9’ Digits come before the uppercase letters ‘0’ < ‘… < ‘9’ < … < ‘A’ < … < ‘Z’ < … < ‘a’ < … < ‘z’ Only one more!!

12. One more character There are lots of punctuation marks and control codes in ASCII (256 codes, after all!) You do NOT have to know these! Except for one special character – the space ‘ ‘ is the first printable character – it comes before all the others you have seen here ‘ ‘ < … < ‘0’ < … < ‘9’ < … < ‘A’ < … < ‘Z’ < … < ‘a’ < … < ‘z’ Know this!