CSCI-100 Introduction to Computing

1. CSCI-100Introduction to Computing Hardware Part III

2. Data Representation • Binary Numbers!!! • Sound  pitch  number  binary number • Letter  number  binary number • Image  color at each pixel  number  binary number • But how many bits are needed to store n symbols? • Or, how many bits are needed to represent n numbers? log2n

3. Output Devices: Engaging our Senses • Output devices are peripheral devices that enable us to view or hear the computer’s processed data • Visual output – Text, graphics, and video • Audio output – Sounds, music, and synthesized speech

4. Monitors • A monitor is a peripheral device which displays computer output on a screen • Types of monitors: • Cathode-ray tube (CRT) • Liquid Crystal Display (LCD or flat-panel) CRT LCD

5. Screen Talk • Monitor size - measured as a diagonal line across the screen • Pixels (or picture element) - tiny dots that compose a picture • Resolution- the number of pixels displayed on the screen (the higher the resolution, the closer together the dots)

6. Printers • A printer is a peripheral device that produces a physical copy or hard copy of the computer’s output • Inkjet printermakes characters by inserting dots of ink • Letter-quality printouts • Cost of printer is inexpensive but ink is costly • Laser printer works like a copier • Quality determined by dots per inch (dpi) produced • Color printers available • Expensive initial costs but cheaper to operate per page

7. Temporary (volatile) storage • Data in memory lost if power is lost or program closed • Secondary storage provides long-term storage • Separate from memory • Common media • Magnetic disks, optical disks, magnetic tape

8. Storage Technologies • Magnetic– Storage devices that use disks or tapes that are coated with magnetically sensitive material • Optical– Storage devices that use laser beams to read patterns etched into plastic disks

9. Optical Disk Storage • Microscopic indentations called pits scatter the laser beam’s light. A light-sensing device receives no light from the pits. A signal is sent to the computer corresponding to a 0 in the binary system • Flat, reflective areas, called lands, bounce the light back to the light sensing device, which sends a signal corresponding to a 1 Disk surface magnified Cross-section of a disk

10. CD-R and CD-RW Discs and Recorders • CD-R • Discs can be read and written to • Discs can only be written to “once” • CD-R drives are capable of reading and writing data • CD-RW • Discs can be read and written to • Discs are erasable • Discs can be written to many times • CD-RW drives are capable of reading, writing, and erasing data

11. Program Execution • Controlled by two special-purpose registers: • Program counter: address of next instruction • Instruction register: current instruction • Machine Cycle • Fetch, Decode, Execute

12. The machine cycle

13. Layers of Abstraction

14. Machine language • Binary sequences interpreted by the computer as instructions, not very human readable • Programming • A computer with software running on it. Want to write nice abstract High level Language (e.g., C++, Java), have stupid computer that only knows how to execute Machine Language (binary sequences) High level language Machine language compiler Least detail, top level Most detail, bottom level number = number + 1 010100100011100101010110

15. Coordination of many levels (layers) of abstraction Application (ex: browser) Operating System (Mac OSX) Software Compiler Instruction Set Architecture Hardware Processor Memory I/O system Digital Design Circuit Design transistors