Computer Graphics HARDWARE Computers v Computers are automatic

Computer Graphics HARDWARE

Computers v Computers are automatic, electronic machines that – accept data & instructions from a user (INPUT) – store the data & instructions (STORAGE) – manipulate the data according to the instructions (PROCESSING) – store &/or output the results to the user (OUTPUT) v A computer system is composed of hardware and software v Hardware components are the physical, tangible pieces that we can see and touch

Software v Program – a sequence of instructions to accomplish a result – a computer processes information under the direction of a program v Data – information to be processed by a program v Example – Data: for each employee, the employee number, hours worked & hourly pay rate – Program: instructions on how to process the data to produce pay cheques, payroll register, etc.

Hardware

Digital Computers v The computers that we use are digital, not analogue computers v Analogue technology – The signal is directly analogous to the information it represents – The signal is continuous and in direct proportion to the source of the information • In a thermometer, mercury rises in direct proportion to the temperature • In an amplifier or telephone, the electronic voltage signal varies in direct proportion to the frequency and amplitude of the sound waves it represents

Digital Technology v Digital technology – The signal is discrete – The information is broken down into pieces, and each piece is represented separately – Analogue information is measured many times per second (the sampling rate) and each measurement is represented as a number – How music is stored on a compact disc - the disc stores numbers representing specific voltage levels sampled at specific times – Can be used to digitize sound, video, graphics, etc. v Our computers work with digital technology, hence the term digital computers

Storage of Programs and Data v Sampling is only one way to digitize information v Since our computers work ONLY with numbers, everything (not just analogue information such as sound and video) must be converted to numbers – Text (letters and special characters) gets converted to numbers (A = 65), using a standard coding convention called ASCII – Graphics (images), gets broken down into pieces (pixels) and each colour gets a number

Binary Numbers v Devices that store and move information are cheaper and more reliable if they have to represent only two states • A circuit conducts current (1) or does not (0) • A position on a diskette is magnetized in one direction (1) or the opposite direction (0) • A position on a CD is pitted (1) or is not (0) v Once information is digitized, it is represented and stored in memory using the binary number system v A single binary digit (0 or 1) is called a bit v A single bit can represent two possible states, like a light bulb that is either on (1) or off (0) v Permutations of bits are used to store values. All information is represented as combinations of the two digits 0 and 1.

Binary Numbers 1 bit 2 bits 3 bits 4 bits 000 001 010 011 100 101 110 111 v Each permutation can represent a particular item 00 01 10 11 0 1 0000 0001 0010 0011 0100 0101 0110 0111 v 1 bit = 2 choices, a 0 or a 1 v 8 bits = 1 byte = 256 different combinations of 0’s and 1’s N v There are 2 permutations of N bits N v Therefore, N bits are needed to represent 2 unique items 1000 1001 1010 1011 1100 1101 1110 1111

Hardware v Units of measure – All done relative to a Byte (8 bits - 1 character) – KB = Kilobyte - 1 thousand bytes (1024) – MB = Megabyte - 1 million bytes (1, 048, 576) – GB = Gigabyte - 1 billion bytes – TB = Terabyte - 1 trillion bytes

A simplified view of a computer system Monitor Keyboard Central Processing Unit Hard Disk Main Memory Floppy Disk

Hardware Devices v Input Devices (Get information) – Keyboard – Mouse – Scanner v Output Devices (Give information) – Screen/monitor – Printer

Hardware Devices v Processing Device (Arithmetic/logic/repetition) – Central Processing Unit (CPU) • 286, 386, 486, Pentium, K 5, K 6 – Has three basic parts • Arithmetic Logic Unit (ALU) – executes all the arithmetic and logic instructions • Control Unit – decodes instructions and determines which is next to be executed • Buses/Registers – Buses are paths for information entering/exiting the CPU – Registers are memory for processing information

Hardware Devices v Storage – Two types • Primary and secondary v Primary Storage (main memory) – On board memory (located on the motherboard) – Very fast, but expensive – Two types • RAM – Random Access Memory • ROM – Read Only Memory

Hardware Devices v RAM - Random Access Memory – Read/write capability – Contents lost when computer is turned off (volatile) – A program must be in RAM for it to execute – 128 to 256 MB for a typical desktop computer

Hardware Devices v ROM - Read Only Memory – Read but not write capability – Permanent (non volatile) – Stores the preliminary instructions to be executed when the computer is turned on, for example • To check RAM • To check communications with peripheral devices • Bootstrap loader program

Hardware Devices Address 9278 9279 9280 9281 9282 9283 9284 9285 9286 Content 10011010 Each memory cell has a numeric address, which uniquely identifies it Main memory is divided into many memory locations (or cells) Each memory cell stores a set number of bits (usually 8 bits, or one byte) Large values are stored in consecutive memory locations

Hardware Devices v Secondary Storage (secondary memory) – External devices (not on the motherboard); either inside or outside the computer – Store programs and data permanently – Slower, but cheaper • RAM - nanoseconds, Drive - milliseconds – Different sizes/styles • • Floppy Disk - 1. 4 MB (portable) Zip Drive - 100 -750 MB (portable) CD - 650 MB (portable) Jaz Drive – 1 -2 GB (portable) discontinued Hard Disk Drive >=20 GB (not portable) Tape - 50 GB (portable, very slow) Flash drives (portable)

Hardware Devices v Other devices – Port • For connecting peripheral devices • USB, Parallel and serial ports – Modem (internal or external) • For communicating over telephone lines

Output devices

plotter The plotter is a computer printer for printing vector graphics. In the past, plotters were used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers. A plotter gives a hard copy of the output. It draws pictures on a paper using a pen.

plotter

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