1. CS 101 – Aug. 28 A little history Introduce binary numbers

2. Before 1940s Only analog machines, moving parts Specific purpose –Adding machines –Tabulators –Sunrise/sunset, celestial General computing only theoretical interest –Alan Turing

3. 1940s Code-breaking machines in WW 2 General purpose electronic computers –ENIAC, U. of Pennsylvania –ABC, Iowa State –Z3, Konrad Zuse in Germany Transistor (1947) to have impact later von Neumann concept forms basis of computer organization

4. US Army photo

5. 1950s & 1960s Commercially produced computers (IBM) –gradually become more common in industry Programming languages developed to facilitate commands to the machine Colleges begin to teach computing Large and expensive Moore’s Law

7. 1970s & 1980s Integrated circuit (1971) allows computers to become much smaller –Intel chips 4004, 8008, 8086, 80286, etc. Personal (home) computing –Applications for non-specialists Intense competition Internet only used in large companies, universities

8. 1990s & 2000s Computer for communication and mass medium Internet as a virtual library & soapbox Tech companies (Apple, Microsoft, Intel, Nokia,…) mature and gain clout Growing need to manage information

9. Binary Numbers Binary = “base 2” The “2” means each bit is either 0 or 1 To interpret a binary number, use place value system.

10. Place value system In base 10, what does 278 mean? 278 = 2 * 10 2 + 7 * 10 1 + 8 * 10 0 Each digit corresponds to a power of 10

11. Binary example So now let’s try base 2: What is 11010? 1 * 2 4 + 1 * 2 3 + 0 * 2 2 + 1 * 2 1 + 0 * 2 0 More concise to simply say 2 4 + 2 3 + 2 1

12. Powers of 2 2 0 = 1 2 1 = 2 2 2 = 4 2 3 = 8 2 4 = 16 2 5 = 32 2 10 ~ 1 thousand 2 20 ~ 1 million 2 30 ~ 1 billion 2 40 ~ 1 trillion

13. Binary  Decimal In a binary number, each “1” gives you a power of 2 More examples: 11 101 110 1110

14. Questions Let’s say we have 4 bits. What is the lowest number? What is the highest number? Try same experiment with 5 bits.