CIT 211 Chapter 2 Notes
CIT 211 Chapter 2 Notes CIT 211
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This 4 page Class Notes was uploaded by Adriana on Monday February 8, 2016. The Class Notes belongs to CIT 211 at Pace University taught by Ronald Frank in Spring 2016. Since its upload, it has received 18 views. For similar materials see Introduction to Computer Systems in Information technology at Pace University.
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Date Created: 02/08/16
CIT 211 Chapter 2 Automated Computation An automated computation device can: o Accept numeric inputs o Perform computational functions o Communicate results The list above is sometimes summarized as input - process - output (IPO) The list of capabilities is very general and can implement with various devices implemented with underlying technologies based on: o Biology o Mechanics o Electronics o Optics o Quantum mechanics Biological Computing Humans can perform IPO via the electrochemical process of our brain and nervous system Biological "technology" occasionally finds use in computer systems, for example: o Displays that use "organic" LEDs o "Genetic" algorithms for applications such as scheduling Mechanical Computing - Shortcomings Complexity o Implementing complex mathematical functions requires corresponding complex machines o Designing and building complex machines is difficult and expensive Reliability o Mechanical devices are subject to wear, resulting in loss of precision or outright failure o Maintenance requirements are high Speed o The speed at which an automated device "computes" is fundamentally limited by the speed of its moving parts o The mass of mechanical parts combined with wear places a relatively low upper bound on their computational speed For example: How quickly can the crank on the Babbage difference engine be turned without breaking the machine? Data Representation Most forms of automated computing rely on clearly identifiable states of a machine "part" to represent data. The clearly identifiable states provide the basis for representing a binary digit – zero (0) or one (1) - a bit A bit is anything that can exist in two states 8 bits make up one byte Each bit can be in two different positions (true/false, on/off, zero/one) 2 o 2 = 4 Automated computers operating on single-state data inputs produce single-state outputs (A + B = C, C is always a single value if A and B are single values) Quantum physics changes this idea. UNICODE allows 8, 16, & 32 bits which allow for all ideographic characters in Eastern and ancient languages. It is the basis of all operating systems. The first page of UNICODE is ASCII -- a 2 byte form of UNICODE. A Word Processor, as opposed to a text editor, does not store text. It stores text, ASCII codes, and special codes to indicate text formatting. This is why copying a file from Word and putting it into Notepad does not always translate well. Data bits represent information. Quantum Computing "Strange" features of quantum physics: o Quantum particles can exist in multiple states at the same time - a qubit o Quantum "digits" of a multibit data value can store many diff values at one o Quantum computers could crack today's security methods in no time Computer Processors A processor is a device that can perform the following functions o Computations (+, -, , ) o Comparisons (<, =, >≠ ≤ ≥ ) o Data movement among memory, mass storage, and I/O devices An instruction is a command to a processor to perform a specific function (ex: Addition) on specific data inputs Each instruction is relatively simple When a computer "follows an instruction" it's said to be executing the instruction Complex tasks are accomplished by combining many instructions into a program and executing the program You can only execute instructions from main memory General and Special Purpose Processors A general purpose processor: Reads its program instructions from a storage deice The content of the storage device can be changed, this changing the program and the function performed by the processor. A special purpose processor either: Uses program storage that can't be altered (ex: read only memory) Has single program "wired" into the processor Formulas v Algorithms A formula is a complex math relationship that can be "soled" w/ a specific sequence of instruction Algorithms implement "intelligent" behavior o Instructions that implement comparison and branching are sometimes called logical instructions o Uses and, or, & not Storage Computers need to store: o Intermediate processing results o Data o Programs Each storage category has different characteristics including importance, quantity, and access time-frame o They may vary within each category Diff mixes of data chars drive the need for a variety of storage devices and technologies, each tailored to cost effectively match the data characteristics with appropriate device characteristics such as o Speed o Volatility o Cost per bit Communication Capabilities Computers must be able to communicate with: o Humans Vision (video displays & printers for output, scanners & camera for input) Sound (music and beeps for output, speech for input. Mechanics and touch (mouse, keyboard, touchscreen) o Other computers Wired communication (Cat6 or fiber-optic cable) Wireless communication (via infrared or radio frequency transmission and reception) Hardware components On the bus Primary/secondary storage I/O unit CPU Off the bus Users Computers CPU Components A CPU is a general purpose processor that executes instructions Implemented on microprocessor "chips" Modern chips have multiple CPUs in a single chip (ex: Intel Core i7) A CPU is internally divided into regions that perform specialized functions, like a human brain Arithmetic-logic unit (ALU) o Performs computation and logic instructions Registers o Internal storage locations - each holds one data item o Holds inputs to and outputs from the ALU Control Unit o Moves data among registers and other computer system storage locations o Accesses program instructions and executes them (data movement) or directs them (computation and logical instructions) Instruction Register o Where the interpretation of bits occurs Instruction Pointer/Program counter (IP/PC) o Directs where data should go next Memory Address Register (MAR) o Holds the memory location of data that needs to be accessed o Stores the memory address from which data will be fetched to the CPU or the address to which data will be sent and stored Memory Data Register (MDR) o Computer's control unit that contains the data to be stored in the computer storage (e.g. RAM) System Bus The com channel that connects all devices in the computer system Bus speed is a critical factor in determining the overall speed of the computer system Modern computers use additional buses to improve performance o e.g. Storage bus Connects to multiple magnetic disk drives to a single connection point on the system bus CPU memory bus Video bus - for direct transfer of data between memory and the video/graphic control Four Groups: Address lines (carry address bits) Data (carry data bits) Control (e.g. start/stop chip controls) Power & Ground Workstations are high end desktop computers Midrange computer Supports up to several dozen users Mainframe computers scales up the ability to support multiple users and applications Server manages one or more shared resources V = iR Voltage = Current * Resistance The bigger the resistance the smaller the electric current Light The speed of light in a vacuum is the universal cap for the speed of light. Light does not lose much energy travelling through a fiber. Functional Abstraction Describe what's going on without paying attention to the details. Gives you the ability to build up from binary to Artificial Intelligence in ideas
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