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| == Reference page for I600 exam == | | == Statistics I604 == |
| ----
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| Exam help wiki: [https://wiki.itcollege.ee/index.php/Exam_help][https://wiki.itcollege.ee/index.php/User_talk:Lphanvan#Storage_abstractions]
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| == Useful linux commands ==
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| '''Checking information'''
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| *'''lsb_release -a''' to check OS
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| *'''uname -sr''' to check OS kernel
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| *'''cat /proc/cpuinfo''' and check processor information.
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| *'''arch''' to check CPU architecture
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| *'''cat /proc/meminfo''' to check memory usage, RAM
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| *'''lspci -t -v -nn''' to enumerate PCI and PCI Express devices
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| *'''lsusb and lsusb -t''' to enumerate USB devices
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| *'''fdisk -l''' to enumerate disks and partitions
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| *'''lsblk''' to enumerate block devices
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| *'''xrandr''' to enumerate display outputs
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| *'''cat /proc/asound/cards''' to check which audio devices are available
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| *'''dmidecode''' to see even more information about your computer
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| *'''ifconfig -a or ip addr list''' to list all network interfaces
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| *'''iwconfig or iw list''' to list all wireless network interfaces
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| *'''hcitool dev''' to list bluetooth host controller.
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| *'''glxinfo''' to check 3D rendering capabilities, GPU
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| *'''lscpu''' info about cpu and processing units
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| *'''lshw - short''' info about hardware units, such as cpu, memory, disk, usb controllers, network adapters
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| *'''hwinfo –short''' info about hardware utility stuff
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| *'''lspci''' info about pci buses and devices connected to them
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| *'''lsscsi''' info about sata/scsi devices
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| *'''lsusb''' info about usb controllers and devices
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| *'''lsblk''' block information, harddrive partitions
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| *'''df –H''' info about disk space and partitions that are mounted
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| *'''fdisk –l''' info about partitions
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| *'''free –m''' info about used, free and total amount of RAM
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| *'''hdparm –i''' info about sata devices
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| '''Editing files'''
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| == Linux Command Line ==
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| ls list files and directories
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| ls -a list all files and directories
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| mkdir make a directory
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| cd directory change to named directory
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| cd change to home-directory
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| cd ~ change to home-directory
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| cd .. change to parent directory
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| pwd display the path of the current directory
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| '''cp (copy)'''
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| cp file1 file2 is the command which makes a copy of file1 in the current working directory and calls it file2
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| What we are going to do now, is to take a file stored in an open access area of the file system, and use the cp command to copy it to your unixstuff directory.
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| First, cd to your unixstuff directory.
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| % '''cd ~/unixstuff'''
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| Then at the UNIX prompt, type,
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| % '''cp /vol/examples/tutorial/science.txt''' .
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| Note: Don't forget the dot . at the end. Remember, in UNIX, the dot means the current directory.
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| The above command means copy the file science.txt to the current directory, keeping the name the same.
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| (Note: The directory /vol/examples/tutorial/ is an area to which everyone in the school has read and copy access. If you are from outside the University, you can grab a copy of the file here. Use 'File/Save As..' from the menu bar to save it into your unixstuff directory.)
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| Exercise 2a
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| Create a backup of your science.txt file by copying it to a file called science.bak
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| '''2.2 Moving files'''
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| '''mv (move)'''
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| '''mv file1 file2 moves (or renames) file1 to file2'''
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| To move a file from one place to another, use the mv command. This has the effect of moving rather than copying the file, so you end up with only one file rather than two.
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| It can also be used to rename a file, by moving the file to the same directory, but giving it a different name.
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| We are now going to move the file science.bak to your backup directory.
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| First, change directories to your unixstuff directory (can you remember how?). Then, inside the unixstuff directory, type
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| % mv science.bak backups/.
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| Type ls and ls backups to see if it has worked.
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| '''2.3 Removing files and directories'''
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| rm (remove), rmdir (remove directory)
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| To delete (remove) a file, use the rm command. As an example, we are going to create a copy of the science.txt file then delete it.
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| Inside your unixstuff directory, type
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| % cp science.txt tempfile.txt
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| % ls
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| % rm tempfile.txt
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| % ls
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| You can use the rmdir command to remove a directory (make sure it is empty first). Try to remove the backups directory. You will not be able to since UNIX will not let you remove a non-empty directory.
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| Exercise 2b
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| Create a directory called tempstuff using mkdir , then remove it using the rmdir command.
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| '''2.4 Displaying the contents of a file on the screen'''
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| clear (clear screen)
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| Before you start the next section, you may like to clear the terminal window of the previous commands so the output of the following commands can be clearly understood.
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| At the prompt, type
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| % clear
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| This will clear all text and leave you with the % prompt at the top of the window.
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|
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| '''cat (concatenate)'''
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| The command cat can be used to display the contents of a file on the screen. Type:
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| % cat science.txt
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| As you can see, the file is longer than than the size of the window, so it scrolls past making it unreadable.
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|
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| '''less'''
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| The command less writes the contents of a file onto the screen a page at a time. Type
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| % less science.txt
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| Press the [space-bar] if you want to see another page, and type [q] if you want to quit reading. As you can see, less is used in preference to cat for long files.
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|
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| '''head'''
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| The head command writes the first ten lines of a file to the screen.
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| First clear the screen then type
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| % head science.txt
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| Then type
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| % head -5 science.txt
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| What difference did the -5 do to the head command?
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|
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| '''tail'''
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| The tail command writes the last ten lines of a file to the screen.
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| Clear the screen and type
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| % tail science.txt
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| Q. How can you view the last 15 lines of the file?
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|
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| '''2.5 Searching the contents of a file'''
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| Simple searching using less
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| Using less, you can search though a text file for a keyword (pattern). For example, to search through science.txt for the word 'science', type
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| % less science.txt
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| then, still in less, type a forward slash [/] followed by the word to search
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| /science
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| As you can see, less finds and highlights the keyword. Type [n] to search for the next occurrence of the word.
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|
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| grep (don't ask why it is called grep)
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| grep is one of many standard UNIX utilities. It searches files for specified words or patterns. First clear the screen, then type
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| % grep science science.txt
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| As you can see, grep has printed out each line containg the word science.
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| Or has it ????
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| Try typing
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| % grep Science science.txt
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| The grep command is case sensitive; it distinguishes between Science and science.
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| To ignore upper/lower case distinctions, use the -i option, i.e. type
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| % grep -i science science.txt
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| To search for a phrase or pattern, you must enclose it in single quotes (the apostrophe symbol). For example to search for spinning top, type
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| % grep -i 'spinning top' science.txt
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| Some of the other options of grep are:
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| -v display those lines that do NOT match
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| -n precede each matching line with the line number
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| -c print only the total count of matched lines
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| Try some of them and see the different results. Don't forget, you can use more than one option at a time. For example, the number of lines without the words science or Science is
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| % grep -ivc science science.txt
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| | Primary Study Materials: |
| | '''Course Homepage:''' http://www.cs.ioc.ee/ITKStat |
| | '''e-Book:''' http://onlinestatbook.com/Online_Statistics_Education.pdf |
|
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|
| '''wc (word count)'''
| | Primary Software: |
| | | '''R:''' https://www.r-project.org/ |
| A handy little utility is the wc command, short for word count. To do a word count on science.txt, type
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| % wc -w science.txt
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| '''To find out how many lines the file has, type''' | |
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| % wc -l science.txt
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| == NMAP and SSH ==
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| '''NMAP'''
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| *Find my ip: ifconfig
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| *Scan networks: nmap <ip>
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| *Find live hosts: nmap -sP 192.168.0.*
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| *Scan specific port: nmap -p 80 server2.tecmint.com
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| *Scan a single ip address: nmap 192.168.1.1
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| *Scan a host name: nmap server1.cyberciti.biz
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| *Scan a host name with more info : nmap -v server1.cyberciti.biz
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| *Scan with disabled port scan: nmap -sn 192.168.2.1/24
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| *Read and scan from txt file: nmap -iL /tmp/test.txt
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| *Create the txt file to read from: cat > /tmp/test.txt
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| *Shut down a network: <sudo> shutdown -s -m \\192.168.1.1 or '''shutdown -h now'''
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| * nmap --iflist
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| '''SSH'''
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| *Connect: ssh collie.stanford.edu
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| *Log-in: ssh jhawkins@collie.stanford.edu
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|
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|
| == Instruction sets == | | == Python I703 == |
|
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| nstruction sets may be categorized by the maximum number of operands explicitly specified in instructions.
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|
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| (In the examples that follow, a, b, and c are (direct or calculated) addresses referring to memory cells, while reg1 and so on refer to machine registers.)
| | Get an idea what to do by next week. Ideas: |
| | '''1. Pyglet,pygame or kivy for a game or simulation:''' |
| | 1.1. MP beat em' up |
| | 1.2. Survival space sim, use webcam for dynamic view |
| | 1.3. Planet rotation simulation |
| | '''Check out ''' |
| | http://nehe.gamedev.net/ |
| | http://learnpythonthehardway.org/ |
|
| |
|
| C = A+B
| | '''2. WebApp''' |
| | 2.1. Budget Management with a GUI |
|
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|
| * 0-operand (zero-address machines), so called stack machines: All arithmetic operations take place using the top one or two positions on
| | '''Notes:''' |
| the stack: push a, push b, add, pop c. | | * Set up RPi web-server |
| C = A+B needs four instructions. For stack machines, the terms "0-operand" and "zero-address" apply to arithmetic instructions, | | * Use '''XMind''' to map the idea first |
| but not to all instructions, as 1-operand push and pop instructions are used to access memory. | | * Run basic website and deploy webapp to it. |
| | | * Check out RPi components and sensors. |
| *1-operand (one-address machines), so called accumulator machines, include early computers and many small microcontrollers: most instructions | | * Buy a breadboard. |
| specify a single right operand (that is, constant, a register, or a memory location), with the implicit accumulator as the left operand
| | * Check out Notepad++ |
| (and the destination if there is one): load a, add b, store c.
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| C = A+B needs three instructions.
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| *2-operand — many CISC and RISC machines fall under this category: | |
| CISC — move A to C; then add B to C.
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| C = A+B needs two instructions. This effectively 'stores' the result without an explicit store instruction.
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| CISC — Often machines are limited to one memory operand per instruction: load a,reg1; add b,reg1; store reg1,c;
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| This requires a load/store pair for any memory movement regardless of whether the add result is an augmentation
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| stored to a different place, as in C = A+B, or the same memory location: A = A+B.
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| C = A+B needs three instructions.
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| RISC — Requiring explicit memory loads, the instructions would be: load a,reg1; load b,reg2; add reg1,reg2; store reg2,c.
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| C = A+B needs four instructions.
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| *3-operand, allowing better reuse of data:[5] | |
| CISC — It becomes either a single instruction: add a,b,c
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| C = A+B needs one instruction.
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| or more typically: move a,reg1; add reg1,b,c as most machines are limited to two memory operands.
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| C = A+B needs two instructions.
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| RISC — arithmetic instructions use registers only, so explicit 2-operand load/store instructions are needed:
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| load a,reg1; load b,reg2; add reg1+reg2->reg3; store reg3,c;
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| C = A+B needs four instructions.
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| Unlike 2-operand or 1-operand, this leaves all three values a, b, and c in registers available for further reuse.[5]
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|
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|
| | == Web Application Programming I702 == |
| | | |
| LDA - Loads the contents of the memory address or integer into the accumulator
| | '''node.js''' |
| ADD - Adds the contents of the memory address or integer to the accumulator
| | '''ngix''' |
| STO - Stores the contents of the accumulator into the addressed location
| | '''nchan''' |
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| ADD ;add one number to another number
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| SUB ;subtract one number to another number
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| INC ;increment a number by 1
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| DEC ;decrement a number by 1
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| MUL ;multiply numbers together
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| OR ;boolean algebra function
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| AND ;boolean algebra function
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| NOT ;boolean algebra function
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| XOR ;boolean algebra function
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| JNZ ;jump to another section of code if a number is not zero (used for loops and ifs)
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| JZ ;jump to another section of code if a number is zero (used for loops and ifs)
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| JMP ;jump to another section of code (used for loops and ifs)
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| 1 LDA #12 ;loads the number 12 into the accumulator
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| 2 MUL #2 ;multiplies the accumulator by 2 = 24
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| 3 SUB #6 ;take 6 away from the accumulator = 18
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| 4 JNZ 6 ;if the accumulator <> 0 then goto line 6
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| 5 SUB #5 ;take 5 away from the accumulator (this line isn't executed!)
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| 6 STO 34 ;saves the accumulator result (18) to the memory address 34
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| Addressing Mode Symbol Example Description
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| Memory Location LOAD 15 15 is treated as an address
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| Integer # LOAD #15 15 is treated as a number
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| Nothing HALT Some inst. dont need operands
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| == Truth Tables ==
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| '''Logical Conjunction(AND)''' | |
| p q p ∧ q
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| T T T
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| T F F
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| F T F
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| F F F
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| '''Logical Disjunction(OR)'''
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| p q p ∨ q
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| T T T
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| T F T
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| F T T
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| F F F
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| '''Logical NAND''' | |
| p q p ↑ q
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| T T F
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| T F T
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| F T T
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| F F T
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| '''Logical NOR''' | |
| p q p ↓ q
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| T T F
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| T F F
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| F T F
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| F F T
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| == Compression ==
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| Data compression ratio is defined as the ratio between the uncompressed size and compressed size:
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| Compression Ratio = Uncompressed Size / Compressed Size
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| Thus a representation that compresses a 10MB file to 2MB has a compression ratio of 10/2 = 5, often notated as an explicit ratio, 5:1 (read "five" to "one"), or as an implicit ratio, 5/1. Note that this formulation applies equally for compression, where the uncompressed size is that of the original; and for decompression, where the uncompressed size is that of the reproduction.
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| Sometimes the space savings is given instead, which is defined as the reduction in size relative to the uncompressed size:
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| Space Savings = 1 - Compressed Size / Uncompressed Size
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| Thus a representation that compresses a 10MB file to 2MB would yield a space savings of 1 - 2/10 = 0.8, often notated as a percentage, 80%.
| |
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| For signals of indefinite size, such as streaming audio and video, the compression ratio is defined in terms of uncompressed and compressed data rates instead of data sizes:
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| Compression Ratio = Uncompressed Data Rate/ Compressed Data Rate
| |
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| and instead of space savings, one speaks of data-rate savings, which is defined as the data-rate reduction relative to the uncompressed data rate:
| |
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| Data Rate Savings = 1 - Compressed Data Rate / Uncompressed Data Rate
| |
| For example, uncompressed songs in CD format have a data rate of 16 bits/channel x 2 channels x 44.1 kHz ≅ 1.4 Mbit/s, whereas AAC files on an iPod are typically compressed to 128 kbit/s, yielding a compression ratio of 10.9, for a data-rate savings of 0.91, or 91%.
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| When the uncompressed data rate is known, the compression ratio can be inferred from the compressed data rate.
| |
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| == Bits and Bytes ==
| |
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| bit byte
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| bit 1 0.125
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| byte 8 1
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|
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|
| | '''Useful links:''' |
| | http://enos.itcollege.ee/phpmyadmin/ |
| | http://enos.itcollege.ee/~ksaareme |
|
| |
|
| Notes:The value of K (Kilo) during calculations can take two values 1024 or 1000, depends on which type of calculation you want to perform. | | '''W3C validation:''' https://validator.w3.org/ |
| Consider using K = 1024 when you are considering storage capacity whether in hard disk, DVDs, flash drives or other devices and storage media.
| |
| K = 1000 should be used when you are thinking of throughput, ie the speed at which information is transferred.
| |
|
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|
| Example: If your computer has 1 KB of disk space is says that he has 1024 B of space, now the throughput of your network card is 1 KB/s then
| | == Node.js == |
| it is said that it transmits data to 1000 B/s.
| |
|
| |
|
| | Stuff about node.js. |
|
| |
|
| | == Operating Systems == |
|
| |
|
| Bit (b)
| | Command line: |
| Byte (B)
| |
| Kilobit (Kb)
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| Kilobyte (KB)
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| Megabit (Mb)
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| Megabyte (MB)
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| Gigabit (Gb)
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| Gigabyte (GB)
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| Terabit (Tb)
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| Terabyte (TB)
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|
| |
|
| == Git ==
| | '''Options modify the behavior of commands:''' |
| | ls -a lists all contents of a directory, including hidden files and directories |
| | ls -l lists all contents in long format |
| | ls -t orders files and directories by the time they were last modified |
| | Multiple options can be used together, like ls -alt |
| | '''From the command line, you can also copy, move, and remove files and directories:''' |
| | cp copies files |
| | mv moves and renames files |
| | rm removes files |
| | rm -r removes directories |
| | '''Wildcards are useful for selecting groups of files and directories''' |
|
| |
|
| The object database contains four types of objects:
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|
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|
| A blob (binary large object) is the content of a file. Blobs have no file name, time stamps, or other metadata.
| |
| A tree object is the equivalent of a directory. It contains a list of file names, each with some type bits and the name of a blob
| |
| or tree object that is that file, symbolic link, or directory's contents. This object describes a snapshot of the source tree.
| |
| A commit object links tree objects together into a history. It contains the name of a tree object (of the top-level source directory),
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| a time stamp, a log message, and the names of zero or more parent commit objects.
| |
| A tag object is a container that contains reference to another object and can hold additional meta-data related to another object.
| |
| Most commonly, it is used to store a digital signature of a commit object corresponding to a particular release of the data being tracked by Git.
| |
|
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|
| | '''Redirection reroutes standard input, standard output, and standard error.''' |
|
| |
|
| | '''The common redirection commands are:''' |
| | > redirects standard output of a command to a file, overwriting previous content. |
| | >> redirects standard output of a command to a file, appending new content to old content. |
| | < redirects standard input to a command. |
| | | redirects standard output of a command to another command. |
|
| |
|
| '''heads'''
| | '''A number of other commands are powerful when combined with redirection commands:''' |
| refers to an object locally.
| | sort: sorts lines of text alphabetically. |
| '''remotes'''
| | uniq: filters duplicate, adjacent lines of text. |
| refers to an object which exists in a remote repository.
| | grep: searches for a text pattern and outputs it. |
| '''stash'''
| | sed : searches for a text pattern, modifies it, and outputs it. |
| refers to an object not yet committed.
| |
| '''meta'''
| |
| e.g. a configuration in a bare repository, user rights. The refs/meta/config namespace was introduced resp gets
| |
| used by Gerrit (software)[clarification needed][45]
| |
| '''tags'''
| |
| see above.
| |
