Development of Computers

1. Development of Computers

2. Hardware 1. Original concept: Charles Babbage 1840’s 2. 4 basic components of a computer system: input store mill output (Now: main memory Central Processing Unit) 3. No success is building a working computer because of the limited technology until the 1940’s)

3. 4. 1st working computer: Mark I (1940) but still partly mechanical. 5. Research was funded by the government because of World War II. 6. 1st all electronic computer: ENIAC (1945-46) Could perform 5000 computations per second! 7. Internally stored program developed by John vonNeumann (Princeton U. math prof.) 8. 1st commercially available computer: UNIVAC (1950 approx. cost: $250,000)

4. 9. 1960’s - mainframes and minicomputers (smaller versions) were developed with smaller and more efficient electronic components: transisters and integrated circuits. 10. Size decreased, cost decreased, but speed and capability increased. 11. 1970’s - personal computers (microcomputers: microprocessor on a silicon chip) 12. 1990’s - supercomputers (one of a kind machines, bigger and more expensive) 13. Today’s computers perform 1,000,000 operation per second.)

5. 14. Future? Molecular size computers BUT they will require radical new technology rather than just the smaller but same technology of the last 30 years. 15. Input devices: keyboard, mouse, floppy disk, hard disk, CD, OCR, scanners, … 16. Output devices: monitor, printer, disk,… 17. Secondary storage (disks, tapes,…) are considered permanent (even though they can be erased, they are not “volotile”).

6. 18. Modem - best described as an interface device. (modulator/demodulator - converts from digital to analog to digital signal).

7. Memory: How does a computer remember? 1. Storage locations are called cells. 2. Smallest addressableamount of memory can hold 1 character and is called a byte. 3. A byte is made up of 8 binary digits (bits) which have only 2 state: on or off ( 1 or 0). 4. Two parts of main storage are RAM - random access memory (volatile) ROM - read only memory (permanent)

8. 5. ROM is only a small amount of storage and is usually measured in kilobytes. 6. RAM is the major part of storage and is measured in megabytes in today’s computers. 7. Both data and programs must be stored in memory before being processed. 8. Data is information of any type: primitive such as integer, real, character or objects such as Strings. 9. ASCII is a commonly used coding system for character data. (28 characters possible.)

9. 10. Example: ‘A’ = 65 = 01000001 ‘a’ = 97 = 01100001 11. Unicode is a recent extension of ASCII in which 216 characters are possible. 12. All instructions as well as data must be coded. Original programs (1950’s) were written in machine language (all 0’s & 1’s) 13. Coding shortens instructions significantly. See pp. 15-16 to compare high level languages, and low level languages (assembler & machine).

10. Processing - the CPU 1. Two parts of the CPU: controller: controls interaction of all parts of the computer system. Ex. fetching instructions handling input & output arithmetic/logic unit: performs all operations +, -, *, /, comparison(<,>,==) 2. We study these in more detail in courses such as computer architecture and operating systems.

11. Networks - the newest aspect of computers to significantly impact our lives. 1. LAN - local area networks (consist of a server, and client machines) 2. WAN - wide area networks (most famous: Internet ( a collection of connected networks). 1st: Arpnet (network of government & research computers) World Wide Web (created in Europe 1989)

12. WWW required more uniformity. Results: HyperTextMarkupLanguage Web Browsers (special programs that execute HTML files and connect with the Internet) platform independent programming language: Java applets - special Java programs which can be embedded in Web pages. Web page - a document or file stored on a computer (somewhere) that is turned on and connected to the Internet. Gateway - a computer that controls access to the Internet.