1. Computer Science 105 RAM and Binary Numbers What is 0000000101? What is 52 in binary? What is a file? Preview Questions:

2. CS 105 FALL 2006 # 2# 2 Random Access Memory (RAM) also called __________ or Primary Memory Stores program instructions and data needed for processing--the working memory (short-term memory) of a computer (like a human’s memory) The primary storage area for programs and data in active use - RAM It is volatile.

3. CS 105 FALL 2006 # 3# 3 Analogy for RAM Imagine you are sitting at a desk. The size of your work area determines how many projects you can handle at once. RAM is somewhat like the that surface – the number of applications that you can run is limited by the size of RAM. RAM is good—get lots of it!

4. CS 105 FALL 2006 # 4# 4 Brain of the computer Brain of the cell phone Brain of the PDA See Unit D in your textbook

5. CS 105 FALL 2006 # 5# 5 The Machine Cycle Main Memory Control Unit Arithmetic/Logic Unit 1 2 3 4 Fetch Decode Execute Store RAM CPU Fetches, Sends back

6. CS 105 FALL 2006 # 6# 6 Digital Cell Phones Digital phones convert your voice into binary information (1s and 0s) and then compress it CDs also convert analog to digital: http://electronics.howstuffworks.com/c d5.htmhttp://electronics.howstuffworks.com/c d5.htm

7. CS 105 FALL 2006 # 7# 7 Main Memory (RAM) Is organized as a sequence of locations Each location can contain a sequence of bits, representing data or an instruction Locations are numbered with “addresses” from 0 to memory-size (can be huge, even gigabytes)

8. CS 105 FALL 2006 # 8# 8 Why use binary numbers? We can build computers that operate in base- 10, but they would be expensive. What is easier than having a switch be ON or OFF? We use electricity that way—low current or high current. High voltages indicate 1 and low voltages indicate 0

9. CS 105 FALL 2006 # 9# 9 Data Representation: Bits The bit is the smallest unit of data; it is 1 or 0, that is, on or off 000 001 010 011 100 101 110 111

10. CS 105 FALL 2006 # 10 Base Ten Numbers –fixed point (usually representing integers) –floating point (decimals) In base 10, a decimal integer means: 587 7 x 10 0 8 x 10 1 5 x 10 2 =7 =80 =500 _______ 587

11. CS 105 FALL 2006 # 11 Base Two Likewise, in base 2, a binary integer means: 101 1 x 2 0 0 x 2 1 1 x 2 2 =1 =0 =4 ---------- 5

12. CS 105 FALL 2006 # 12 Base 2--another way to convert You can remember the places by exponentiation of 2: 1001 means you add 1 and 2^3, or 8 +1

13. CS 105 FALL 2006 # 13 What is this number in decimal?

14. CS 105 FALL 2006 # 14 What is this number in binary? 52

15. CS 105 FALL 2006 # 15 Characters, marks, and more Letters, numbers, line feeds, and non-printing characters ASCII-8. Pronounced “ass-key” ASCII stands for American Standard Code for Information Interchange, has 256 different symbols-all Operating Systems fully understand ASCII. UNICODE allows for up to 65,536 different characters. It is more complex and not implemented on many Operating Systems, but it is on Windows NT and Windows XP.

16. CS 105 FALL 2006 # 16 Different characters held in RAM 00100001 = ???

17. CS 105 FALL 2006 # 17 Why are these lists in alphabetical order?

18. CS 105 FALL 2006 # 18 ASCIIASCII (link) ASCII can use 256 characters -- the foreign language possibilities are below:

19. CS 105 FALL 2006 # 19 ASCII, Cont. 32 is the ASCII code for a space. So 32 = 00100000 in binary, and when the computer gets that data, it causes a space to appear. Note: all the capital letters finish before the lower case letters appear B = 66 b = 98

20. CS 105 FALL 2006 # 20 What is a file? See page 116 in your Concepts book!! A collection of data on a storage medium Filename conventions Filename extension.txt.txt.jpg.jpg.exe.exe.doc.doc

21. CS 105 FALL 2006 # 21 Seeing the three-letter extensions can save you from a virus!

22. CS 105 FALL 2006 # 22 How to see the three-letter extensions on your files.txt = Text file.txt = Text file.sql = MySQL-Front file.sql = MySQL-Front file

23. CS 105 FALL 2006 # 23 Go to Tools/Folder options/View tab Do not hide file extensions

24. CS 105 FALL 2006 # 24 To Summarize: What is 0000000101 in decimal? What is 8 in binary? What is a file?