Information Processing and Coding
The computer is an apparatus for processing information. Information is represented indigital form (binary) and one must distinguish the binary representation of information(one or more binary numbers) of service (its actual content).
Part I: the binary
All information is treated as binary sounds regardless of their meaning. There are threetypes of basic operation:
- Transmit
- Set memory
The computer is an apparatus for processing information. Information is represented indigital form (binary) and one must distinguish the binary representation of information(one or more binary numbers) of service (its actual content).
Part I: the binary
All information is treated as binary sounds regardless of their meaning. There are threetypes of basic operation:
- Transmit
- Set memory
- Calculate
I) The transmission of information
To transmit information from one point to another in digital form, you need a vehicle for information, which will physically effect the transfer. This may be one or more connectingson (son bonding in a circuit, telephone line, railroad track etc..) transmission byelectromagnetic waves or sound, an optical link which uses a beam of light visible or notetc. .
In any case, if the transmission communicates a binary digit at a time (the figures beingtransmitted one after the other) we speak of serial link. If several numbers aretransmitted simultaneously, it is called parallel link. In general, for a transmissiondistance, it uses a serial, parallel interfaces are used only for very short distance.
To transmit information from one point to another in digital form, you need a vehicle for information, which will physically effect the transfer. This may be one or more connectingson (son bonding in a circuit, telephone line, railroad track etc..) transmission byelectromagnetic waves or sound, an optical link which uses a beam of light visible or notetc. .
In any case, if the transmission communicates a binary digit at a time (the figures beingtransmitted one after the other) we speak of serial link. If several numbers aretransmitted simultaneously, it is called parallel link. In general, for a transmissiondistance, it uses a serial, parallel interfaces are used only for very short distance.
For example, inside the computer, information is transmitted by links called parallel busin this case, the number of bits (binary digits) are transmitted simultaneously in generala power of 2: 8,16,32, 64 or even 128 bits. The advantage of the parallel connection isspeed, a 32-bit parallel link is obviously capable of transmitting information 32 times faster than serial.
There are also cables for printers that use a parallel connection (normally 8 bits in this case) but it tends to disappear as the technology has made tremendous progress,speed serial links now widely enough to ensure transferring information to a printer. Thesame remark can be made for devices such as external hard drive, which can now beconnected via USB (Universal Serial Bus).
There are also cables for printers that use a parallel connection (normally 8 bits in this case) but it tends to disappear as the technology has made tremendous progress,speed serial links now widely enough to ensure transferring information to a printer. Thesame remark can be made for devices such as external hard drive, which can now beconnected via USB (Universal Serial Bus).
In any transmission, whether serial or parallel information flows at a certain speed, thisword means in this case the number of bits that can be transmitted per second. Forexample, the first standard for connecting USB (1) had a maximum speed of 20 MbpsThis speed quickly proved inadequate, why has it been a few years later set thestandard USB 2 much faster.
For a parallel connection, to avoid ambiguity, we define the frequency, that is to say thenumber of calls per second on the bus: a bus 8 bits at a frequency of 250 MHz and iscapable of transmitting 8x250 • 106 • 106 = 2000 bits per second, or 2 Gbit / s.
For a parallel connection, to avoid ambiguity, we define the frequency, that is to say thenumber of calls per second on the bus: a bus 8 bits at a frequency of 250 MHz and iscapable of transmitting 8x250 • 106 • 106 = 2000 bits per second, or 2 Gbit / s.
II) Memory
A memory is a device for recording information to restore it later. When recordinginformation in a memory, we talk about writing. When retrieves information from a memory, we talk about reading.
There are different types of memory. Memory (RAM or Random-Access Memory) of a computer is a type of volatile memory, that is to say that disappears when you cut food.The hard disk on the contrary, or devices such as USB sticks are permanent memories,that is to say who remain (theoretically indefinitely) even without a power supply.
When one wants to write or read information in a memory, you must specify the locationof this information.
A memory is a device for recording information to restore it later. When recordinginformation in a memory, we talk about writing. When retrieves information from a memory, we talk about reading.
There are different types of memory. Memory (RAM or Random-Access Memory) of a computer is a type of volatile memory, that is to say that disappears when you cut food.The hard disk on the contrary, or devices such as USB sticks are permanent memories,that is to say who remain (theoretically indefinitely) even without a power supply.
When one wants to write or read information in a memory, you must specify the locationof this information.
In a disk drive or a USB key, the information is grouped into files (in English, file) whichnames are assigned. The computer then uses the file system - for example, FAT32(FAT = File Allocation Table) - to determine the physical location information using thefile name.
In RAM, this process would be much too slow. The information is grouped into bytes (8bits) that are numbered. The order number is called a byte address.
In RAM, this process would be much too slow. The information is grouped into bytes (8bits) that are numbered. The order number is called a byte address.
III) Calculations
The main body of a computer is its CPU (or processor). C'st he who performs thecalculations, and in principle all the information passing through it. This was the case forthe first computers, but now certain types of information are processed by specific circuits such as the graphics card or sound card. In this case, the CPU does not directly address the information graphics or sound, but simply give orders to these globalcircuits (eg, open or close a window on the screen).
The processor directly controls the memory using two buses: the data bus, whichcirculate the binary and drinking places, which indicates the location of the memory cellsor question (s). The data bus is bidirectional, that is to say that information can move thememory to the processor or vice versa. In early computers, it consisted of 8 bits, then to1984-85 it increased to 16 bits and 32 bits very quickly. Currently, most computers havea 32-bit core architecture, even if the memory data bus can be up to 128 bits in order toincrease the rate of exchange.
The main body of a computer is its CPU (or processor). C'st he who performs thecalculations, and in principle all the information passing through it. This was the case forthe first computers, but now certain types of information are processed by specific circuits such as the graphics card or sound card. In this case, the CPU does not directly address the information graphics or sound, but simply give orders to these globalcircuits (eg, open or close a window on the screen).
The processor directly controls the memory using two buses: the data bus, whichcirculate the binary and drinking places, which indicates the location of the memory cellsor question (s). The data bus is bidirectional, that is to say that information can move thememory to the processor or vice versa. In early computers, it consisted of 8 bits, then to1984-85 it increased to 16 bits and 32 bits very quickly. Currently, most computers havea 32-bit core architecture, even if the memory data bus can be up to 128 bits in order toincrease the rate of exchange.
The address bus is unidirectional, it is always the processor determines the memory address in horns treatment. Currently, the address bus has 32 bits, which may indicate232 = 4,294,967,296 memory locations (bytes) different. This number is close to 4billion, and the theoretical maximum capacity is normally empty memory 4 gigabytes (4GB).
The processor has internal memory called registers, which luis used to temporarily storeinformation. Using these records, it can do several types of basic operations. Forexample,
- Charge (Load) information in a register
- Store (Store) the contents of a register in memory
- Modify the contents of a register, for example by taking the binary complement, orshifting (shift) to the right or left bits of the register.
- Add (or do any other operation to two operands) the contents of a register with thecontents of another register or memory and place result in the starting register.
The processor has internal memory called registers, which luis used to temporarily storeinformation. Using these records, it can do several types of basic operations. Forexample,
- Charge (Load) information in a register
- Store (Store) the contents of a register in memory
- Modify the contents of a register, for example by taking the binary complement, orshifting (shift) to the right or left bits of the register.
- Add (or do any other operation to two operands) the contents of a register with thecontents of another register or memory and place result in the starting register.
The successive operations to be performed by the processor are given in a program,which is itself placed in memory. A program consists of instructions that are encoded inbinary cells in consecutive memory and the processor must read one after the other.Each statement gives the order to perform basic operations above views.
Part Two: The information coding
Once defined the transmission, storage andprocessing of information is the most important point: the meaning of the raw binary. How a binary number represents information is called encodingor representation.
Raw information is a set of binary bits (binary digits), often in groups of four (when theinformation is in hexadecimal) or 8 (byte or byte). Abyte represents information that can be written with8 bits or 2 hex digits. For example, 01101100(binary) = 6c (hexadecimal). We also speak oftenof word (word) 16, 32, 64 etc.. bits. In general, thewidth of the word (the number of bits) is a multipleof 8. On a byte, we can represent 28 = 256different values, a word of 16 bits, 216 = 65,536different values, a 32-bit word 232 =4,294,967,296 different values.
Raw information is a set of binary bits (binary digits), often in groups of four (when theinformation is in hexadecimal) or 8 (byte or byte). Abyte represents information that can be written with8 bits or 2 hex digits. For example, 01101100(binary) = 6c (hexadecimal). We also speak oftenof word (word) 16, 32, 64 etc.. bits. In general, thewidth of the word (the number of bits) is a multipleof 8. On a byte, we can represent 28 = 256different values, a word of 16 bits, 216 = 65,536different values, a 32-bit word 232 =4,294,967,296 different values.
The user of the representation of a binaryinformation must choose the
meaning of each of binary values.
meaning of each of binary values.
This can be a single positive integer,in which case the translation is
very simple (seeprevious courses), or an integer positive ornegative,
in which case it generally selects the 2's complement representation,
or a decimal It willthen choose a suitable mode of representation.
very simple (seeprevious courses), or an integer positive ornegative,
in which case it generally selects the 2's complement representation,
or a decimal It willthen choose a suitable mode of representation.
It may also represent many other information such as text, sound, image etc..
It will then set theencoding.
It will then set theencoding.
For example, a digital image is made up of dotscalled pixels (English word
coined from the phrase"picture element"). Each pixel must be defined bycolor
and brightness. We will see later how the coding of images.
coined from the phrase"picture element"). Each pixel must be defined bycolor
and brightness. We will see later how the coding of images.
A sound is defined physically by changes inpressure, and for digitally
encoding the sound iscut time and sliced thin enough to be able torebuild
these changes so rapidly that the human ear is deceived. As the human ear
can hearsounds up to a frequency (theoretical) 20 kHz, we choose to represent
a sound with the pressure values measured at a higher frequency:
48, 96 or144 kHz.
encoding the sound iscut time and sliced thin enough to be able torebuild
these changes so rapidly that the human ear is deceived. As the human ear
can hearsounds up to a frequency (theoretical) 20 kHz, we choose to represent
a sound with the pressure values measured at a higher frequency:
48, 96 or144 kHz.
A text is a sequence of characters, and it willtherefore agree on a numerical code for eachcharacter. There are two codes currently used: thenormal code is the alphanumeric code ASCII(American Standard Code for InformationInterchange) which uses a representation of 8 bits, but it has developed since the late 90's a code of 16 bits (Unicode). When code text (for example, in a word processing file) is given following the codesof characters of text, and add formatting information like font size, color, layout and so on.When you open a word processing file withNotepad, you use only text information, and notthose of formatting.
It must also represent computer programs. A program is a series of instructions for the processor, each instruction is encoded on one ormore bytes, and each type of instruction with a code defined. In addition, the program will requirethe address of the memory cells used by the instructions.
Annex1: different physical media of information transmission
When the binary information is transmitted by one or more son inside a computer, just set the logic levels 0 and 1. For example, standard TTL (inwhich the supply voltage is 5V, the potentials of allpoints of the circuit are between 0 and 5V), logic level 0 corresponds to a potential below 0.8 V, thelevel logic 1 to a potential higher than 2V.
However, when information is transmitted through a medium such as an electromagnetic wave orsound or a light beam guided by an optical fiber, oreven by an electrical signal, it must define howinformation is transmitted. this is done using a typeof modulation.
For example, you can use a periodic signal byvarying the amplitude of the signal representing information to be transmitted. This is calledamplitude modulation. It can also vary thefrequency, for example with a base frequency of101.10 MHz, making it vary from 100.95 to 101.25MHz. This is called frequency modulation. It canalso transmit information using the signal phase.For example, with a symmetrical square signal to begin with, can be modulated (varying) the time at which the signal changes sign, the frequencyremaining the same. This is called phasemodulation.
In defining the physical medium of transmission of information, this media is then able to transmit at a certain speed in bits / s. If this speed is higher than required, then you can combine several differenttransmissions sue the same medium, it is calledmultiplexing. For example, if you have a connectionto 1 Gbps, and we want to transmit telephone calls, which each require 10 Mbps, we can multiplex 100telephone calls on the same physical medium.
The optical fiber transmission is from this point ofview is quite extraordinary: a fiber, we use severaltens of channels (one for each type of light ray) and each channel can transmit at speeds of severalgigabits per second, you can gift over a single optical fiber to transmit several thousands (even up to several million!) of simultaneous phone calls. Table ASCII
Décimal Octal Hex Binaire Caractère
------- ----- --- -------- ------
001 001 01 00000001 SOH (Start of Header)
002 002 02 00000010 STX (Start of Text)
003 003 03 00000011 ETX (End of Text)
004 004 04 00000100 EOT (End of Transmission)
005 005 05 00000101 ENQ (Enquiry)
006 006 06 00000110 ACK (Acknowledgment)
007 007 07 00000111 BEL (Bell)
008 010 08 00001000 BS (Backspace)
009 011 09 00001001 HT (Horizontal Tab)
010 012 0A 00001010 LF (Line Feed)
011 013 0B 00001011 VT (Vertical Tab)
012 014 0C 00001100 FF (Form Feed)
013 015 0D 00001101 CR (Carriage Return)
014 016 0E 00001110 SO (Shift Out)
015 017 0F 00001111 SI (Shift In)
016 020 10 00010000 DLE (Data Link Escape)
017 021 11 00010001 DC1 (XON)(Device Control 1)
018 022 12 00010010 DC2 (Device Control 2)
019 023 13 00010011 DC3 (XOFF)(Device Control 3)
020 024 14 00010100 DC4 (Device Control 4)
021 025 15 00010101 NAK (Negative Acknowledgement)
022 026 16 00010110 SYN (Synchronous Idle)
023 027 17 00010111 ETB (End of Trans. Block)
024 030 18 00011000 CAN (Cancel)
025 031 19 00011001 EM (End of Medium)
026 032 1A 00011010 SUB (Substitute)
027 033 1B 00011011 ESC (Escape)
028 034 1C 00011100 FS (File Separator)
029 035 1D 00011101 GS (Group Separator)
030 036 1E 00011110 RS (Record Separator)
031 037 1F 00011111 US (Unit Separator)
032 040 20 00100000 SP (Space)
033 041 21 00100001 ! (exclamation mark)
034 042 22 00100010 " (double quote)
035 043 23 00100011 # (number sign)
036 044 24 00100100 $ (dollar sign)
037 045 25 00100101 % (percent)
038 046 26 00100110 & (ampersand)
039 047 27 00100111 ' (single quote)
040 050 28 00101000 ( (left opening parenthesis)
041 051 29 00101001 ) (right closing parenthesis)
042 052 2A 00101010 * (asterisk)
043 053 2B 00101011 + (plus)
044 054 2C 00101100 , (comma)
045 055 2D 00101101 - (minus or dash)
046 056 2E 00101110 . (dot)
047 057 2F 00101111 / (forward slash)
048 060 30 00110000 0
049 061 31 00110001 1
050 062 32 00110010 2
051 063 33 00110011 3
052 064 34 00110100 4
053 065 35 00110101 5
054 066 36 00110110 6
055 067 37 00110111 7
056 070 38 00111000 8
057 071 39 00111001 9
058 072 3A 00111010 : (colon)
059 073 3B 00111011 ; (semi-colon)
060 074 3C 00111100 < (less than sign)
061 075 3D 00111101 = (equal sign)
062 076 3E 00111110 > (greater than sign)
063 077 3F 00111111 ? (question mark)
064 100 40 01000000 @ (AT symbol)
065 101 41 01000001 A
066 102 42 01000010 B
067 103 43 01000011 C
068 104 44 01000100 D
069 105 45 01000101 E
070 106 46 01000110 F
071 107 47 01000111 G
072 110 48 01001000 H
073 111 49 01001001 I
074 112 4A 01001010 J
075 113 4B 01001011 K
076 114 4C 01001100 L
077 115 4D 01001101 M
078 116 4E 01001110 N
079 117 4F 01001111 O
080 120 50 01010000 P
081 121 51 01010001 Q
082 122 52 01010010 R
083 123 53 01010011 S
084 124 54 01010100 T
085 125 55 01010101 U
086 126 56 01010110 V
087 127 57 01010111 W
088 130 58 01011000 X
089 131 59 01011001 Y
090 132 5A 01011010 Z
091 133 5B 01011011 [ (left opening bracket)
092 134 5C 01011100 \ (back slash)
093 135 5D 01011101 ] (right closing bracket)
094 136 5E 01011110 ^ (caret circumflex)
095 137 5F 01011111 _ (underscore)
096 140 60 01100000 `
097 141 61 01100001 a
098 142 62 01100010 b
099 143 63 01100011 c
100 144 64 01100100 d
101 145 65 01100101 e
102 146 66 01100110 f
103 147 67 01100111 g
104 150 68 01101000 h
105 151 69 01101001 i
106 152 6A 01101010 j
107 153 6B 01101011 k
108 154 6C 01101100 l
109 155 6D 01101101 m
110 156 6E 01101110 n
111 157 6F 01101111 o
112 160 70 01110000 p
113 161 71 01110001 q
114 162 72 01110010 r
115 163 73 01110011 s
116 164 74 01110100 t
117 165 75 01110101 u
118 166 76 01110110 v
119 167 77 01110111 w
120 170 78 01111000 x
121 171 79 01111001 y
122 172 7A 01111010 z
123 173 7B 01111011 { (left opening brace)
124 174 7C 01111100 | (vertical bar)
125 175 7D 01111101 } (right closing brace)
126 176 7E 01111110 ~ (tilde)
127 177 7F 01111111 DEL (delete)
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