Introduction to computers and programing
Content
• Hardware• Information storage
RAM, ROM HD, DVD
• Display Images Characters (fonts)
• File system/type Encryption Compression
• Network Protocols Packets
• Programming Algorithm Pseudocode Flowchart
• Languages• Source code
Example
The computer
Internally
The connections
Information storage
• 1 bit• 8 bits• 16 bits• 32 bits• 64 bits
• bit (1 or 0)• byte (octet) (28)• word (216)• double (232)• long double (264)
Encoding information on a fixed element of length n with a base b gives bn non-redundant possibilities
Information coding
• Binary 0 or 1
• Octal 0-7
• Hexadecimal 0-9+A-F
• Decimal 0-9
• How to count
• 128+32+16+4+1= 181 (decimal) 265 (octal) B5 (hexadecimal)
• Signed vs unsigned 0 to 255 -127 to +127
128 64 32 16 8 4 2 1
1 0 1 1 0 1 0 1
Operations on bits
• Booleans: 0 = false = no 1 = true = yes
• Operators: AND OR XOR NOT
• Example tablesAND
0 1
0 0 01 0 1
OR 0 1
0 0 11 1 1
XOR
0 1
0 0 11 1 0
RAM/ROM
Memory mappingAddress Values0000 00010002......
..FFFF
• Size reminder:• Kilobyte Kb 210 ~103
• Megabyte Mb 220 ~106
• Gigabyte Gb 230 ~109
• Terabyte Tb 240 ~1012
• Petabyte Pb 250 ~1015
• …
1 0 1 1 1 0 0 1
0 0 0 0 1 1 1 1
1 1 1 0 0 0 1 1
0 0 1 0 0 1 0 0
HD/DVD
track
sector
head
Display
• Screen pixel or dots• Color coding: 32 bits• 1 pixel = 3 bytes of color (RGB)+1
byte alpha channel (transparency)• 1600x1200x4bytes=7,5 Mb!
• Fonts Bitmap Vectors
TrueType, OpenType, PostScript
QuickTime™ et undécompresseur TIFF (non compressé)
sont requis pour visionner cette image.
Keyboard/Mouse
• Each key (or combination of keys) of the keyboard sends a code to the computer.
• The code is interpreted and converted to the corresponding ASCII or Unicode number.
• The mouse movements 1 to 4 bytes (vertical &
horizontal) • Buttons
Clicked, pressed, rolled
buttons
ASCII & Unicode
• ASCII 7/8 bits• Unicode
UTF-8/16/32 bits ISO-8859 (Latin)
• od -c od -h
•
Software layers
ROM
Hardware
Operating System
User Interface
Software
Files
CPU, RAM, HD, DVD
Word, scripts, mail, web browser…
Data (.doc, .mp3)
BIOS
Linux
CLI, X-Windows
Windows
Windows
MacOSX
Firmware
Quartz
File systems
• Method the OS uses to store information Storage unit, directories, subdirectories (Windows,
VMS) Single arborescence (Linux, MacOSX, all Unix)
• What exactly is a file? a piece of information (text, graphic, data, music
program, script) it is identified by a name and an logical address (or
path) other informations: date, size, type, creator,
ownership, physical address…
File system organisation
Disk 1 Disk 2
Directories
Subdirectories
Windows
DOCS PROGS
WORD EXCEL
CONFIG DATA
EXPT1 EXPT2
/
/usr /home
phil johnlocal
bin lib
emacs X11
Unix
D:C:
Disk 1
Disk 2
Path
• The path is the logical address used by the system or the user to locate a file.
• Example:/bd_du_Palais/35/etage/4/appart/12/Dupont_ Jean.txt
filenamesuffix
path
File types
• Executable .exe .app Unix requires « x »
• Data Text (.txt) Music (.mp3) Image (.jpg, .gif) Movie (.mpg, .mov) Binary (.bin)
• Special cases in Unix STDIN STDOUT STDERR
Encryption / compression
• Compression Reducing the size of files E.g., .mp3, .gz, .jpg, .zip
• Encryption Protecting your privacy E.g., .pgp
• Packing Grouping the files E.g., .tar
Networks
• Direct USB 11Mb-480Mb Ethernet 10Mb-1Gb
• Wired Modem 56Kb ADSL 600Kb-8Mb LAN 10Mb-10Gb
• Wireless Bluetooth 1Mb-20Mb WIFI (AirPort) 11Mb-54Mb
Network (ethernet or wireless)
• Computer talk to each other via network protocols ip, tcp, http, ftp, …
• TCP/IP transmission control
protocol/internet protocol
• Handshaking• Transmission• Ackowledgement
• DNS Domain Name Server
• URL Universal Resource
Locator• IP addess
192.42.197.51
DNS reminder
Primary DNS
Root DNS
Local DNS
Client query Target server
1
2 3
45
6
www.expasy.org
129.194.8.64
*.org
dns.anywhere.net
client.anywhere.net
www.expasy.org ??
Packets
The data travels within units called packets
Packet breakout
Usual TCP/IP payload per packet: 512 bytes
Introduction to programming
What is a program?
• How to cook?• The algorithm• Are you a programmer?
Pseudocode
• This is the pseudocode for a game of Monopoly
Flowcharts
Flowcharts details
Languages
• Low level (processor dependent) Machine code, assembler
• High level: structured, procedural Fortran, C, Pascal…
• High level: object oriented C++, Java, C#, Perl, Objective-C…
• Virtual machines Java, C#…
• Scripting Perl, Python, JavaScript…
Source code -> Object code
• Compiler+linker Fortran, C, Pascal, C++…
• Interpreter Basic, Perl…
• Intermediate Java
• Compiler+linker Fast to execute, but slow
to debug• Interpreter
Slow to execute, but fast to debug (no need to recompile)
• Intermediate Slow…
Source code
• Instructions Statement, blocks Affectation Operators Loops Tests Subroutines Comments
• Data structures Variable List Array Hash Pointers Objects
Source code (2)
• Statement, blocks One or more
instructions for the processor
• Affectation Change to a variable
• Operator affect one or more
variable + * - / AND OR NOT…
• Variable A region in memory
that can be modified Exists in different
types Scalar, char, numeric,
boolean List, array Hash Combination->data
structure
Source code (3)
• Loops Allow the computer to
repeat blocks• Tests
Decide what to do• Subroutines
Programs frequently called (functions)
• Comments The most important
lines of the source code…
• Pointers Reference to region in
memory (address)• Objects
Combination of data and code
Example: a text to treat
« Noon rings out. A wasp, making an ominous sound, a sound akin to a klaxon or a tocsin, flits about. Augustus, who has had a bad night, sits up blinking and purblind. Oh what was that word (is his thought) that ran through my brain all night, that idiotic word that, hard as I'd try to pun it down, was always just an inch or two out of my grasp - fowl or foul or Vow or Voyal? - a word in a quizz which, by association, brought into play an incongruous mass and magma of nouns, idioms, slogans and sayings, a confusing, amorphous outpouring which I sought in vain to control or turn off but which wound around my mind a whirlwind of a cord, a whiplash of a cord, a cord that would split again and again, would knit again and again, of words without communication or any possibility of combination, words without pronunciation, signification or transcription but out of which, notwithstanding, was brought forth a flux, a continuous, compact and lucid flow: an intuition, a vacillating frisson of illumination as if caught in a flash of lightning or in a mist abruptly rising to unshroud an obvious sign - but a sign, alas, that would last an instant only to vanish for good. »
Gilbert Adair
Result…
a=97
b=15
c=26
d=35
f=23
g=32
h=44
i=90
j=1
k=5
l=33
m=17
n=91
o=104
p=15
q=1
r=43
s=59
t=77
u=52
v=4
w=31
x=2
y=13
z=2
Do you see any problem??
Try with this:
« The quick brown fox, jumps over the lazy dog. »
Flowchart
Source code example
#!/usr/bin/perl -w # essential line of all perl scripts
$filename = "avoid.txt"; # affect « avoid.txt » to the variable $filename
# open the file, or exitopen(FILE, $filename) || die "Cannot open file ‘$filename’\n\n";@text = <FILE>; # add each line of the file to an arrayclose FILE;
foreach $line (@text) { # read one line from the array into $line and repeat for each line @table = split(//,$line); # read each character of the line in an array while ($char=pop(@table)) { # read one character of the array 'table' and repeat for all
$char =~ s/[^a-z]//; # keep only the alphabetical character a to z if ($char) { # check if the character exists and execute the block
$count{$char}++; # if yes, increment by one the hash 'count'
} }
}
# print each character and its number of occurence one per lineforeach $c (keys %count) {
print "$c=$count{$c}\n";}exit; # quit the program
Tips
• Think about your problem
• Create a flowchart• Create the
pseudocode• Verify the memory
used by your variables
• Write the code
• Test the code For all the possible
functions or cases (if possible)
Give it to users as a beta (if not possibe)
Sell it (if you work for Microsoft©… ;-)
• Debug
Summary of the week
• Monday Intro computers &
programming Intro Unix Tutorial Unix
• Tuesday Intro Perl Regexp & Perl In-liners
• Wednesday Object Oriented
programming BioPerl EMBOSS
• Thursday Database indexing BLAST HTML & cgi-bin
• Friday Finish exercises Users questions
Unix
• Next presentation…
Vassilios Vassilios aliasalias
UnixMan!!!UnixMan!!!
