--- --- restore content begins
Information layer reading notes
Chapter 2 binary value and number system
2.1 Digital and Computing
- Digital : abstract mathematical unit belonging to a system, subject to rules specific order, addition and multiplication rules rules, which include a natural number, negative, rational, irrational numbers and the like.
- A natural number (natural number): 0 or any number obtained by repeatedly applied to the 01.
- Negative (negative number): number of 0 to less than plus minus numeral is obtained before the corresponding positive number.
- Integer (integer): a natural number, negative or zero natural number.
- Rational (rational number): integer quotient or two integers.
2.2 positional notation
- Base : counting system basic value, the predetermined system used in the digital and the value of the number of bit positions
- Positional notation : one kind of expression of a digital system, arranged in order digit, each digit has a bit value of the digital value of each digit and the sum of the products of value and.
- The importance of 0: 0 to discover the unlimited potential of the human mind, no other human innovation can bring such a far-reaching impact on the development of human intelligence. --Georges Ifrah
2.2.1 binary, octal and hexadecimal
NOTE: Any numeration system is smaller than the maximum number of the base 1, for example, in base 10 numbering system having ten digits (0-9).
Operating a binary, octal and hexadecimal to decimal conversion performed exactly the same
2.2.2 Other numeration system operation
- Note that the binary adder "carry" the use of
- Note that the binary subtraction "borrow" to use
- Similar operation is found by comparing the binary decimal arithmetic rules
2.2.3 a power of 2 as the base number system
1. convert a binary number to octal, from the rightmost binary digits start, with each group of three digits, corresponding to each converted into digital octal number.
The reason can quickly convert a binary number between 2 and 8 octal number that is a power of two (there is a similar relationship between binary and hexadecimal)
3. represents a hexadecimal number four binary number
2.2.4 converted to decimal number system other numbers
- Decimal conversion rules relate to the new base of the division.
- If you use another form to describe
the While (quotient is not zero)
with a new base in addition to the decimal
to the left as the remainder of the answer to the next number
in place of the decimal number using a commercially
2.2.5 binary values and Computer
- Binary digit (binary digit): digit binary numeration system, either 0 or 1.
- Bit (bit): short for binary digit.
- Byte (byte): 8 binary bits.
- Word (word): one or more bytes, is referred to as digit word length of the computer.
summary
- 1. The number is written in positional notation, where the number in sequence, each number having a bit value, the value equal to the product of each number with its bit values.
- 2. The bit value is the radix number system power.
- 3. The computer hardware used is a binary number.
Chapter 3 Data Representation
3.1 Data and Computer
- Data (Data) : base value or facts.
- Information (Information) : or tissue with an effective way of processed data.
- The computer can store, represent and assist us in modifying various types of data, including:
* Digital
* Text
* Audio
* images and graphics
* Video - Multimedia (Multimedia) : Several different types of media.
- Bandwidth (bandwhich) : maximum transferred from one location to another location of bits or bytes within a fixed time.
- Data Compression (Data compression) : reducing the space required to store one piece of data.
1. The compression ratio (compression ratio): size of data after compression by dividing the value of the original data size.
2. lossy compression (lossy compression): 'll lose data compression technology.
3. lossless compression (lossless compression): do not lose data compression technology.
3.1.1 analog data and digital data
- Nature of most of them are continuous and unlimited of.
- Data representing the two methods: analog method and a digital method
- Analog data (Analog Data) : a continuous form information represented.
- Digital data (Digital Data) : a discrete version of information represented.
- Digitizing (Digitize) : dividing the information into discrete segments.
- Why modern computer use and management are binary values?
Because if the device storage and management of data need only represent one of two values, then the cost is much smaller, but also much more reliable. If only the electrical signal to transmit binary data, but also easy to maintain. - PCM (Pulse-code Modulation) : jump signal changes between the two extremes.
- Re-timing (ReClock) : Before too much signal degradation to reset it to its original state behavior.
Note: As long as the clock is reset before the signal degradation too much, they will not lose information.
3.1.2 binary notation
- Generally, an n-bit binary number can be represented by 2 ^ n states, it may be formed as n-bit digital combination of 2 ^ n 0 and 1.
Note: Whenever available-digit increase in a number of states will be represented twice. - A computer architecture capable of addressing and the number of bits of a moving minimum , usually a power of 2 , such as 8, 16 or 32.
Thus, any type of data assigned to the minimum amount of memory is typically a multiple of a power of two.
3.2 Digital data representation
3.2.1 negative representation
- Numerical symbol representation (Signed-Magnitude representation) : Classification notation (positive or negative) number belongs, represents the value of the digital representation of the magnitude of the number.
* Performing addition and subtraction operations on signed integers can be described as a certain number of units moved in one direction or the other direction. - The number of fixed length
perform addition in this mode, only two summed number, and then discard the carry can, so that the pattern drawn decimal complement concept.
Decimal complement (complement Ten apos) : negative one kind of representation, using negative I k-th power minus 10 I FIG. - Twos complement
Note: If the number of the leftmost bit is "0", then that figure is positive; if it is "1" means that this number is negative.
A more simple method to calculate the binary complement: the inverse of each bit plus one. Advantages : allows you to immediately recognize in the two's complement of a number is positive or negative. - Overflow (overflow): : reserved bits to save any results condition value calculated.
Overflow: Overflow is boundless world map to the typical problem occurs on a limited machine. No matter how many bits to a digital distribution, the total number of potential needs expressed these bits can not be met.
3.2.2 Real notation
- Real number having an integer part and a fractional part .
- Decimal (radix point): In the numeration system, to a real number into an integer part and fractional part of the point.
Note : In decimal, the decimal point is to the right of the tenths , percentile , and so on; in binary, decimal point is to the right of the binary bits , four bits , and so on. - Real value : non-integer values.
It can be any real value by the sign (positive or negative), mantissa and exponent - Floating-point representation (Floating Point) : marked symbols, real mantissa and exponent representation.
Define the real value of the decimal formula: The symbol × × 10 ^ exp mantissa
formula defined real-valued binary: the symbol × × 2 ^ exp mantissa - Scientific notation (Scientific Notation) : Another floating-point representation.
3.3 Text Representation
- Character Set (Character the SET) : a list of characters and express their code.
3.3.1 ASCII character set
- Original ASCII character set with 7 represent each character, you can represent 128 different characters. The eighth bit of each byte is used as the first parity bit . Later Latin-1 extended ASCII character set can represent 256 characters, including some key characters and add a few special symbols.
Note : Each ASCII character has its own order, which is the storage they use the code decision.
3.3.2 Unicode character set
- Created by objective : that all the characters in all languages spoken in the world, including Asian ideographic symbols, in addition, it also represents a number of supplementary special characters, such as scientific notation.
Note : a convenience Unicode character set is that it's at the ASCII character set as a subset. Unicode character set can be said is designed to be a superset of ASCII.
3.3.3 Text Compression
- Letter information (text) is a basic data type.
- Keyword coding (encoding keyword) : instead of the usual words with a single character.
A key code. Limitations : 1 is used for character encoding of the keyword can not appear in the original text. 2. Text feature can limit the number of words and coding to encode
two A key coding extension is replaced with special characters in a specific text mode.
Three coding key advantage is generally higher than the coding mode frequency whole word; but disadvantage is coded pattern is typically relatively short, for each word, the replacement of the relatively small space-saving thereof. - Run length encoding (RUN-length encoding) : number of times to replace their recurring repeat a series of characters. Aliases : iterative encoding
Note : In the run-length encoding, the sequence of repeated characters are replaced as a symbol character, characters and repeated explanation behind the increase in the number of repetitions of numeric characters. - Huffman coding (Huffman encoding) : The character of the variable-length binary string, so that characters having a common short code.
3.4 audio data representation
- A stereo system by sending an electrical signal to a speaker to produce sound. This signal is an acoustic analog representation .
- In general, the sampling rate per 40,000 or so times is enough to create a reasonable sound reproduction. Sampling rate is higher than this value, the human ear to hear the sound will be distorted.
- The overall effect sound is affected by many factors, including the quality of the equipment, the sound and the type of hearing people and so on.
- Plastics LP is an analog representation of sound waves.
3.4.1 Audio Format
- Popular audio formats: WAV, AU, AIFF, VQF and MP3.
Note : While all formats are based on a voltage value obtained from the sampled analog signal, information details, but they are different ways formatting, compression techniques are also different.
3.4.2 MP3 audio format
- MP3 format uses lossy compression and lossless compression two of the compression method.
3.5.1 Color notation
- Color is usually the RGB (Red-Green-Blue) values indicate that this is actually a three digits, each of the primary colors described relative share .
- Color Depth : the amount of data used to represent the color, usually represented by the number of bits to represent a color depth of color.
- Enhanced color: it refers to the color depth of 16-bit color.
- True color: color refers to the color depth of 24 bits.
3.5.2 Digital Image and Graphics
- Pixels (Pixel) : isolated dots used to represent the image, the representative image element.
- Resolution (resolition) : the number of pixels used to represent the image.
- ** raster graphics format (the format Raster-Graphics) : pixel storage format of the image information by one.
Several popular raster graphics formats are Bitmap (BMP) , GIF and JPEG .
A .GIF image only by the constitution ** 256 colors, GIF files best suited for less color graphics and images, so it is stored line images are the preferred format .
Two .JPEG use of the characteristics of the human eye, it is seen as storing photos color image preferred format. It uses compressed mode is quite complex, effectively reducing the generation of the file size.
Three .PNG image compression generally better than the GIF image, the color depth while also providing a wider range. However, PNG image does not support animation , but also not as widely supported GIF format.
3.5.3 Vector graphic representation
- Vector Graphics (Vector Graphics) : representation of the image by segments and geometry. It is also described a series of directions segment , line width and color of command.
- Raster graphics and vector graphics comparison : For the grating pattern of different size and proportions have to be repeated coding, vector graphics can be resized by mathematical calculation, these changes may be calculated dynamically as needed.
However , vector graphics are not suitable for representing real-world images. - The Internet's most popular vector graphics formats are Flash , image storage to create its image requires Flash binary format, a dedicated editor .
3.6 video representation
- Video codec (Video CODEC) : A method for reducing the size of the movie, the movie can be played on a computer or network.
- Video codec employed compression method : time compression and spatial compression .
A time compression (temporal compression) : Film compression technique based on the difference between successive frames.
Second spatial compression (Spatial compression) : compression technology based on the movie still image compression technology.
Note : 1 keyframe is the difference between the comparative frame of reference, its complete image will be saved. 2. For continuous image, save only the changed portion ( delta frame ). - Today's popular video codecs: Sorenson, Cinepak, MPEG and Video Real .
summary
A. Since the computer can operate a binary value, so that all types of data must be represented as a binary form.
Second, data may be divided into two categories: continuous (analog) and discrete (digital) .
Three integer value represented by the binary values of their corresponding representation has negative symbolic numerical representation and complement notation .
IV. The character set is alphabetic and numeric characters and represents the list of their code.
V. The audio information is represented as sound waves digital.
VI. The method shows the basic images are bitmap and vector graphics .
VII. Video is divided into a number expressed as a static image of the image .
--- end --- restore content