【正文】 WMF, PICT, EPS, SVG, SWF, and TrueType fonts curve：曲線， mathematical formula：數(shù)學(xué)公式 計(jì)算機(jī)導(dǎo)論 Representing Video To simulate motion, movies need to record (and play back) at least 12 frames per second. However, good sound quality requires 24 frames/s. 24 frames/s = 1440 frames/minute = 46400 frames/hour If each frame has a resolution of 1024 x 768* there are 786,432 pixels in a frame. If the colour of each pixel is stored as 24 bits (3 bytes) of data, one frame alone requires 2,359,296 bytes (2 MB) of memory. An hour of film then, requires 203,843,174,400 bytes (194,400 MB – more than 190 Gigabytes) of storage – just for the images. video：視頻 frame：禎 計(jì)算機(jī)導(dǎo)論 Data Compression(數(shù)據(jù)壓縮 ) ? It is important that we find ways to store and transmit data efficiently, which leads puter scientists to find ways to press it. ? Data pression is a reduction in the amount of space needed to store a piece of data. ? Compression ratio is the size of the pressed data divided by the size of the original data. Data pression :數(shù)據(jù)壓縮 Compression ratio：壓縮比 計(jì)算機(jī)導(dǎo)論 Data Compression ? A data pression technique can be – lossless, which means the data can be retrieved without any loss of the original information, – lossy, which means some information may be lost in the process of paction. ? As examples, consider these 3 techniques: – keyword encoding （關(guān)鍵字編碼） – runlength encoding （掃描寬度編碼） – Huffman encoding （霍夫曼編碼） Lossless：無(wú)損 Lossy：有損 計(jì)算機(jī)導(dǎo)論 ? Numbers, text, images, audio, and video are all forms of data. Computers need to process all types of data. ? All data types are transformed into a uniform representation called a bit pattern for processing by puters. ? A bit is the smallest unit of data that can be stored in a puter. ? A bit pattern is a sequence of bits that can represent a symbol. ? A byte is 8 bits. SUMMARY 計(jì)算機(jī)導(dǎo)論 ? Coding is the process of transforming data into a bit pattern. ? ASCII is a popular code for symbols. ? Images use the bitmap graphic or vector graphic method for data representation. The image is broken up into pixels which can then be assigned bit patterns. ? Audio data are transformed to bit patterns though sampling, quantization, and coding. ? Video data are a set of sequential images. SUMMARY (continued) 計(jì)算機(jī)導(dǎo)論 EXERCISES ? 21； 22； ?211； 212； 213； 214； 215 ?223； 224； 225； 226； 227 ?234； 235； 236； 237； 238； 239 Number Representation Chapter 3 天津大學(xué)軟件學(xué)院 計(jì)算機(jī)導(dǎo)論 Number System ? The Decimal system is based on 10， 09； ? The binary system is based on 2， 01； ? Octal notation is based on 8， 07； ? Hexadecimal notation is based on 16 ， 09， AF。Data Representation Chapter 2 天津大學(xué)軟件學(xué)院 計(jì)算機(jī)導(dǎo)論 DATA TYPES(數(shù)據(jù)類(lèi)型 ) Data today e in different forms such as numbers, text, images, audio, and video. People need to process all these data types. The puter industry uses the term “multimedia” to define information that contains numbers, text, images, audio, and video. number：數(shù)值 text：文本 image：圖像 audio：音頻 Video：視頻 Multimedia:多媒體 計(jì)算機(jī)導(dǎo)論 Analog and Digital (模擬和數(shù)字 ) Information ? Computers are finite（有限的） . Computer memory and other hardware（硬件） devices have only so much room to store and manipulate a certain amount of data. The goal of data representation（ 數(shù)據(jù)表示） is to represent enough of the world to satisfy our putational needs and our senses of sight and sound. 計(jì)算機(jī)導(dǎo)論 Analog and Digital Information ? Information can be represented in one of two ways: analog or digital. Analog data A continuous representation, analogous to the actual information it represents. Digital data A discrete representation, breaking the information up into separate elements. 計(jì)算機(jī)導(dǎo)論 Analog and Digital Information A mercury thermometer exemplifies analog data as it continually rises and falls in direct proportion to the temperature. Digital displays only show discrete（離散的） information. 計(jì)算機(jī)導(dǎo)論 DATA INSIDE THE COMPUTER All data types from outside a puter are transformed into a uniform representation when stored in a puter and then transformed back when leaving the puter. This universal format is called a bit pattern（位組合格式） . BIT（位） A bit (binary digit) is the smallest unit of data that can be stored in a puter。 it is either 0 or 1. BIT PATTERN（位組合格式） A bit pattern is a sequence, or as it is sometimes called, a string of bits that can represent a symbol. . BYTE（字節(jié)） A bit pattern of length 8 is called a byte. 計(jì)算機(jī)導(dǎo)論 Examples of bit patterns 計(jì)算機(jī)導(dǎo)論 REPRESENTING DATA TEXT（文本） A piece of text in any language is a sequence of symbols used to represent an idea in that language. You can represent each symbol with a bit pattern. In other words, text such as ―BYTE‖, which is made of four symbols, can be represented as 4 bit patterns, each pattern defining a single symbol. 計(jì)算機(jī)導(dǎo)論 How many bits are needed in a bit pattern to represent a symbol in a language? The length of the bit pattern that represents a symbol in a language depends on the number of symbols used in that language. More symbols mean a longer bit pattern. The relationship is not linear。 Decimal system:十進(jìn)制 binary system：二進(jìn)制 Octal notation：八進(jìn)制 Hexadecimal notation：十六進(jìn)制 計(jì)算機(jī)導(dǎo)論 DECIMAL AND BINARY Two numbering systems are dominant today in the world of puters: decimal and binary. DECIMAL SYSTEM 計(jì)算機(jī)導(dǎo)論 BINARY SYSTEM The binary system is based on 2. There are only two digits in the binary system, 0 and 1. 計(jì)算機(jī)導(dǎo)論 OCTAL NOTATION Octal notation is based on 8. This means there are 8 symbols: 0,1,2,3,4,5,6,7. Bit Pattern 000 001 010 011 Oct Digit 0 1 2 3 Bit Pattern 100