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Lecture 1E Introduction

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					   Катедра Информационни технологии и комуникации




         Informatics

(The Science of Information
         Systems)

      Lecture 1 – Introduction

                   2011
Textbook

       J.Glenn Brookshear, Computer Science, An
Overview, 10th edition, Addison Wesley / Pearson
eddition, 2007




                                                   2
Scope of the Course

 The course has the aim to explain:

    •What is data and how it is presented in computers
    •What are algorithms, computer programs, Programming languages
    •What are the Computer architectures
    •How to store data and what is Data base management system (DBMS)
    •How to exchange data between computers
    •What is Operating system
    •What is application software
    •Which are the most used computer technologies
    •What is Information system
    •What is Internet and its generations
    •What is Information security
    •How to design Information systems
    •What are the eBusiness applications
    •Project management
    •How to make Blogs and Websites
                                                                        3
Received practical knowledge and experience

    During the Labs the students will receive knowledge and experience for
  design and using Information systems dedicated to Corporated and Public
  sector organisations
    Each student will be able to design small information system, using the
  available in the PC Office products
    The work will be in team by 2
    The information systems will be build using the two Microsoft products
       oMS Excel
       oMS Access


   There will be Course works for each team
   There will be 2 tests
   The exam will be via test
   The final marks will be as a result of the Exam, Tests and the Course
  work

    Every student has to create its own Blog and its own WebSite –
  compulsory
                                                                              4
Origin of Computers
    Initial ideas – from Greek and Roman civilization – Abacus - for addition
    Some beginner ideas
        oBlaise Pascal (1623-1662) – a machine for addition using gear with zero
        positioning
        oCharles Babbadge (1792-1871) – a machine for addition, with printing on
        paper; with the other arithmetic operations; punching of commands for
        execution
    Idea for algorithm – sequence of holes on paper
        oJoseph Jacquard (1752-1834) – developed a weaving loom with weaving
        o
        process determined by holes in paper cards
    Idea for representing data – via holes on paper
        oHermann Hollerith (1860-1929)
        oHis work was the base for establishment of IBM Co
    Using electricity and electronics in 1900’s
    1940 – Bell Laboratories – Mark I –electronically controlled mechanical relays
    1937-1941 John Atanasoff-Berry – first computer on electronic tubes - в Iowa
  State College
    Mainframes (1950-60)
    Mini computers (1960-70)
    Personal computers (1970-80)
                                                                                     5
The science of Algorithms
  Extending the computer capabilities of execution sequence of commands leaded
to evolution of algorithms

  Gödel incompleteness theorems have created the conditions to have few
command sequences performing the same results – options for solutions / options
for algorithms

 In the world 2 sciences have been established :
     oComputer Science – a science for algorithms
     oInformation Systems – a science for creation computer systems

 Working with algorithms, there are few questions:
   oWhich problems can be presented via algorithms
   oWhich problems is reasonable to solve via algorithms run on computers
   oHow easy is to create (discover) an algorithms
   oHow to analyse and evaluate algorithms
   oHow to treat data
   oHow to provide intelligent computer behavior using algorithms
   oWhat is the influence on the societies using algorithms
                                                                                  6
Information systems

•The Information system is a complex of hardware and software elements,
linked into an integrated system, providing data treatment of an organisation

•Information system has an aim to support the execution of the business in the
organisation, involving people, documents, data processing technologies,
procedures for running the system

•To support the entire business, the Information systems use many different
Information and Communication Technologies (ICT)

•There are information systems supporting only a part of the corporate
business, called Sub-systems of the Information system, e.g. Accounting
system, Stock control system, HR system, CAD systems, etc.




                                                                                 7
Base system for presenting numbers
   Each system consisting of symbols and rules for their use, for presenting any
 number. In base 10, the symbols are: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
   The symbols are digits; Position in the number can be or not important
   Non-positional system(Rome) – VII, и positional (decimal ) systems - 71
   Conversion of numbers from one base to another base
      •Example for conversion the decimal number 121 into base 2 (using only the
      digits 0 and 1)
      121:2=60                   remainder 1
       60:2=30                   remainder 0
       30:2=15                   remainder 0
       15:2=7                    remainder 1
        7:2=3                    remainder 1
        3:2=1                    remainder 1
        1<2                final remainder 1
          The result is 1111001 in base 2
     •Example of conversion of decimal number 201 into base 16 (using the digits
     0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F)
     201:16=12                  remainder 9     (9)
       12<16             final remainder 12     (C)
          The result is C9 in base 16
                                                                                   8
Binary arithmetic (1 of 2)
 •Using the digits 0 and 1
 •Addition
      0+0 = 0                     10110
      0+1 = 1                + 11011
      1+0 = 1                -------------------
      1+1 = 10                  110001
      1+1+1=11
 •Subtraction
      0-0 = 0                     11000101
      1-0 = 1                -      1101100
      1-1 = 0                     --------------------
     10-1 = 1                       1011001
 •Multiplication
      0х0 = 0                11001
      0x1 = 0             x    1101
      1x0 = 0                -------------
      1x1 = 1                11001
                            00000
                           11001
                         11001
                        =============                    9
                        101000101
Binary arithmetic (2 of 2)

 •Division – using multiplication and subtraction
 •Example – to divide 10000,111 on 10,1
 10000,111:10,1 = 1 0 0 0 0 1,1 1 : 1 0 1 = 1 1 0,1 1
                    - 101
                      -------
                         110
                       - 101
                        ---------
                               11                   (cannot be subtracted with positive result)
                        - 101
                           --------
                               111
                            - 101
                             ----------
                                 101
                              - 101
                               -----------
                                  000
                                                                                                  10
Grouping of binary data in computers
•Minimal unit – 1 bit

•Unit for operation – 1 byte = 8 bits
     •There are binary operations, but there are not used too often

•Word – 4 bytes

•Double word – 8 bytes

•A character is presented via:
     oSingle byte – most often used code tables
     o2 bytes – for covering all languages, including Chinese and Japanese
•There a few internationally standardised Coding tables for correspondence between
a symbol and its binary representation:
     oASCII – main symbols are coded in 7 bit combinations, while the other
     alphabets (Cyrillic, Scandinavian, some French /German characters) is used the
     8th bit for coding. This Coding table is used in PC, Unix servers, MS. The table has
     94 printable characters
     oEBCDIC – use all 8 bits for coding. Applied for Mainframes
     oUnicode – uses 2 bytes for represent a symbol – for coding more than 100,000
     symbols                                                                            11
Number representation in computers
 •The numbers are presented in computers as
      •Fixed point numbers
      •Floating point numbers
      •Binary-decimal numbers
 •Fixed point numbers are integer, with fixed position of the point (binary point)


        sign
                                Value of the number

 •Floating point numbers have mantissa, exponent and sign



  sign           exponent                                 mantissa
  (+)
                  (27)                                    (397485)


 •Binary-decimal numbers use 4 bits for each decimal digit representation. The
 number is presented via sequence of such 4 bit constructions

               1 0 0 1 0 1 1 1 0 0 1 0 0 1 0 1                       => 9725
                  9         7             2           5                              12
Fixed point numbers
•They are integer
•The negative numbers are presented in 2’ Complement code
   Positive number                             Negative number
   0 000 0000 0000 1010 => (+10)               1 111 1111 1111 0110 =>(-6)

•Using 2’ Complement code, the operation Subtraction is converted to Addition
     А-B = A + (-B) -> A + (B)2’Compl

•There are 2 systems for presenting Fixed point numbers, depending where is MSB (the
Most Significant Bit)

     •MSB is on left

       знак
                            стойност на числото


     •MSB is on right

       знак
                            стойност на числото
•The length is 4 bytes / 8 bytes. In 4 bytes the possible numbers amount is +- 2 billion 13
Floating point numbers

  •Floating point numbers have advantages to Fixed point numbers, that they
  can present any non-integer number

  •The mantissa is treated as number based on 16. For this reason the exponent
  works on base 16 as well

  •The sign represent the sign of the mantissa. There is no place for the sign of
  the exponent. The exponent uses 7 bits. The exponent in the Floating point
  representation is always positive and it is for 0 to 127. This is a machine
  meaning exponent and it corresponds to the real exponents from -64 to +63.

  •The length is 8 bytes or 16 bytes, where only the mantissa varies.

  •The Floating point numbers are not only used in scientific calculations; they
  are used always where numbers can be non-integer.




                                                                                    14
Logical (Boolean) operations
 •In computers the information is presented in binary form

 •The variables can have values 0 or 1. There is a special algebra, created by Boole,
 working with truth vales. This algebra is applied in computers and it is called
 “Boolean algebra” or “Logical operations”.

 •The Boolean function can have 2 options as value – truth or false, presented in
 the computers as 1 or 0.

 •Boolean functions are defined most often in tables


                  X value        Y value         X&Y vale


                    0              0                0

                    0              1                0

                    1              0                0

                    1              1                1


                                                                                        15
Main Boolean functions and their realisation in
computers
•Logical AND                         •Logical Exclusive OR
  X            Y   X&Y                    X               Y        X^Y
                                          0               0         1
  0            0    0
                                          0               1         0
  0            1    0
                                          1               0         0
  1            0    0
                                          1               1         0
  1            1    1


  X     (1)                                   (1)
                                         X
                        X & Y (0)                                       X^Y   (0)
  Y (0)                                  Y (0)



•Logical OR                          •Negative
  X            Y   X|Y                         X              -X
  0            0    0
                                               0              1
  0            1    1
                                               1              0
  1            0    1
  1            1    1

  X      (1)                                  X     (1)
                                                                         -X     (0)
                         X|Y   (1)
      Y (0)                                                                     16
Components for building Computers (1 of 4)

 •Trigger – component for storing information of a Boolean variable


                   R                                   Q
     Reset Input                                              Output




                                                        Q
                   S
      Set Input




                        R                  Q
                                Тr
                        S




                                                                       17
Components for building Computers (2 of 4)

  •Register – component for storing an information word – Byte, Word, Double
  word, etc.



  Q7         Q6           Q5           Q4           Q3           Q2           Q1           Q0


    Q            Q            Q            Q            Q            Q            Q            Q

        Тr           Тr           Тr           Тr           Тr           Тr           Тr           Тr
    R            R            R            R            R            R            R            R
             S            S            S            S            S            S            S            S




        S7           S6           S5           S4           S3           S2           S1           S0




                                                                                                            18
Components for building Computers (3 of 4)
    •Adder (Summer) – executes operation Addition of 2 numbers
    •Adder is the main component for doing Addition, Subtraction (via 2’s
    Complement code), Multiplication and Division
    •Addition is made by n equal action of Adders

                                                                                  Si


Xi          Yi       Ci-1       Si        Ci
0           0         0         0         0

0           0         1         1         0
                                                                            ∑
0           1         0         1         0

0           1         1         0         1              Ci                                    Ci-1
1           0         0         1         0
                                                                          Xi Yi
1           0         1         0         1

1           1         0         0         1

1           1         1         1         1                 S3         S2                 S1                  S0

                                                     ∑             ∑               ∑                   ∑

                                               C3            C2           C1               C0                 InC
                                                    X3 Y3         X2 Y2           X1 Y1               X0 Y0
                                                                                                        19
Components for building Computers (4 of 4)
 •Logical circuit of Adder
           Ci                Si




    . . . . ..
        . .
  . . .
  .
  Xi
            . .                     Yi       Ci-1   20

				
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