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CSCI-100 Introduction to Computing. Hardware Part III. 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?
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CSCI-100Introduction to Computing Hardware Part III
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
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
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
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)
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
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
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
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
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
Program Execution • Controlled by two special-purpose registers: • Program counter: address of next instruction • Instruction register: current instruction • Machine Cycle • Fetch, Decode, Execute
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
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