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Computer Applications

Visual summary of my lecture "computer applications" - last update WS 2017/18

Prof. Dr. Klaus Hardt

on 10 September 2017

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Transcript of Computer Applications

Topics of the lecture
"Computer Applications"

WS 2017/18
Input devices
Types of computers
Liquid Crystal Display /
Thin Film Transistor
CRT - Cathode Ray Tube
the smallest unit is a
1 bit corresponds to a single yes/no alternative
so with one bit we can code two different values
next unit is a
1 byte = 8 bit
1 kilobyte = 1024 byte
1 megabyte = 1024 kilobyte
1 gigabyte = 1024 megabyte
1 terabyte = 1024 gigabyte
a physical system is needed which shows exactly two distinct states.
Punch card -> punched/not punched
Magnetic coil -> right/left hand magnetic field
Electrical switch -> open/closed
Transistor -> conducting/non-conducting
Moreover, the system needs to be addressable, i.e. every storage cell has to be clearly identifiable.
The binary representation of text is based on
. That means you define a binary code for each text character.

The most famous code which is available on all computers is the
ode of

For coding it uses
7 bit
. With this exactly 128 characters can be coded. Thereof the first 32 characters are non-printable characters, e.g. "cr - carriage return".
This amount is therefore not sufficient for special characters such as the German Umlaute "ä, ü, ...". Likewise, many languages have more than 128 characters.
By now, obsolete technique, but still partly in use.

Generating light by stimulation of
material by use of an
electron beam

Cathode -> generates electrons
Anode -> accelerates the electrons to sufficient energy
Magnets -> for deflection of the electron beam
Dot mask -> arranged in front of the phosphor material for focussing of the electron beam
Phosphor -> generates the light pulse
Vacuum tube -> ensures vacuum

Generating colour by three different phosphor materials. These generate red, green and blue light => additive colour mixing.
Light generation by phosphor material is also used in Plasma Screens, but without electron beams.
Entirely different principle than the CRT.
light source
light is polarized by
light passes
LCD cell
; depending on applied voltage the direction of polarization can be rotated
allows light of the right direction of polarization to pass through
generating color by triple amount of LCD cells with each time different
color filters
that let

through red, green and blue light => additive color mixing
Most important type of monitor nowadays!
The performance parameters are still oriented by the system structure of the "von Neumann scheme".
main memory
: in case of PCs directly plugged in on the motherboard; very fast access, but "briefly"; typical values for PCs = 2 - 4 GByte
clock speed
: every computer has an "internal clock" that specifies a fixed processing speed; typical values = 1,5 - 3 GHz
processing unit
-> MIPS (Million Instructions per Second) and FLOPS (Floating Operations per Second); important performance characteristics especially for mainframes. At this, you particularly use the size FLOPS
bus width
: characterizes the number of possible addresses in the processing unit; today the transition of 32 bit to 64-bit systems increasingly occurs in the PC area
We distinguish between different types of computers that can be differentiated with regards to size and usage. Of course, the transitions are flowing.
(Personal Digital Assistant): portable computer; today they can only barely be distinguished by smartphones.
Tablet Computer
: new variant; became very popular in the last years
: mobile computer;
: desktop computer; huge success story since IBMs 486; today increasingly replaced by notebooks
: "bigger" PC, normally with fixed integrated graphics; application particularly for server and visualisation
: very powerful system with many users simultaneously or very high computing capacity
are still the "classic" input devices. They are increasingly complemented by touch screens, thus touch-sensitive monitor surfaces.

An important addition, especially in the field of graphical image processing, are digitizer tablets. While "movement" is detected with a mouse, the digitizer tablet determines the position of a mouse or a pen. This is especially helpful for drawing. This is realized by crosswise laid wired that are infused in e.g. ceramics or plastic.

In order to transfer pictures in a computer, scanners and digital cameras are used ==>
We can distinguish between three "generations":
drum scanner
flatbed scanner
digital cameras
(Today) They all have the usage of CCD elements for the image capture in common. Thereby shows:
the drum scanner (in principle) one CCD element
the flatbed scanner one CCD row
the digital camera a two-dimensional CCD-array

CCD elements convert light into electrical power.
The amount of electricity should (preferably) be proportional to the impinging amount of light in such a way that the brightness can be measured.
A color scan is done by usage of three CCD elements per pixel with different color filters that each only let through the red, green and blue amount of light.
Number systems
In order to understand how numbers can be depicted in a binary storage system, it is helpful to deal with number systems.
Hereby, we use so-called (positional) notation systems. In doing so, the value of a number is defined by the symbol value and the position value (usually calculated from right to left).
First of all, for every number system it needs to be determined how many different digits are used (=
) and how they are depicted (symbols determined by historical and cultural context).
The position
result from the powers of the base, always starting with the value 1 (Base power zero).
Decimal System
the number system that we are familiar with:
Base =
Digits ("symbols") => 0 1 2 3 4 5 6 7 8 9
Position values => 1, 10, 100, 1000, etc.


413 = 3*
+ 1*
+ 4*
(Please note: from right to left!)
Dual System
Base =
Digits => 0 1
Position values => 1, 2, 4, 8, 16, 32 etc.


10011 = 1*
+ 1*
+ 0*
+ 0*
+ 1*

This system directly fits to the binary information storage because exactly TWO different digits are used.
Hexadecimal System
Base =
Digits => 0 1 2 ... 9 A B C D E F
Position values => 1, 16, 256, etc.

F8 = 8*
+ 15*

This number system is widely spread in computer science because it depicts numbers in a compact form and the transformation from and to the dual system is very simple.
ASCII 8 bit extension
By using the 8th bit another 128 characters can be coded.
Additionally, various language tables/ character sets are utilized which can be used alternatively and thereby provide different languages.

The amount of character codes thereby is 256. This is not sufficient for several languages.
The coding of all worldwide used text characters is possible by using
2 byte
per character.

Hereby, the most prevalent coding is the
Test procedures
It is necessary to be able to test the read or transferred digital information. As you certainly cannot "see" it in every bit if it is correct, additional information has to be saved or transferred to the data-bits that is used for the check-up of digital data.
-> saves an additional bit per byte in such a way that the amount of "1" is odd in total ("odd parity")
-> saves a complete testbyte additionally to the testbits in regular intervals so that the amount of "1" on each bit-position is also odd. This allows the correction of mistakes.
check sum
-> handles the bytes as numbers, adds them up and saves/transfers the whole sum as a check value.
-> more complex calculation of a test value
Computer systems
Now and then also called supercomputer; twice each year a list of the 500 fastest computers in the world is issued, the so-called "TOP 500" list.

By now, a processing power of PetaFlops is reached. As a whole, the development over a long period of time still shows "Moore's law", thus an exponential increase.

The huge performance is primarily not reached by using a particularly fast processor, but by
interconnecting a great many processors
( > 100000) and working parallel on a task.
In general, we see two contrary developments for computer systems.
On the one side, an increasing miniaturization and mobility of the systems.
On the other side, regaining strength of mainframes or "super computer" that is even supported by "cloud computing".
Storage media
Storage media
Storage media use a physical effect in order to save digital information, thus bits. So, at least two clearly differentiable physical states have to exist.
We distinguish depending on the applied effect:
magnetic storage media
- they use different magnetic orientations as information medium
optical storage media
- they use the different reflection of light
semiconductor storage media
- they use the different concentration of charge carriers in a semiconductor crystal
Magnetic storage media
Still one of the most important types of storage media. We distinguish between:
magnetic tapes
- flexible plastic tape with magnetizable surface; especially applied for backup of data because only sequentially access ("fast-forward and rewind"); formatting in form of traces (typically 9 trace tapes).
floppy disks
- today generally not relevant for PCs anymore; circular wafer with magnetizable surface, therefore circular tracks; the tracks are subdivided in sectors that always contain the same amount of data (typically 512 byte)
magnetic hard disks
- still the most common storage media in computers; they use a disk pack where both sides of the wafers are coated
Hard disk
disk pack
is used in which both sides of the wafers are coated. Tracks lying on top of each other are called

The write-/read head has a minimum distance to the surface and should never land on the surface.

The wafers rotate with high speed, typically:
7200 rpm
(rounds per minute).
Optical storage media
With these media the
of light is modified in order to save information. The most important factors are:
(Compact Disc); storage volume ~ 700 MB
(Digital Versatile Disc); storage volume ~ 4,5 GB
Blue Ray
Disc; storage volume ~ 25 GB

Bits are encoded by the
of "
" to "

There is
helical track from the inside to the outside.

By usage of rewritable discs the reflection on the surface is obtained by the molecular change of the substrate. Higher laser energy reverses this change during the erasing procedure.
Semiconductor storage media
Typical factors of these storage media are
USB sticks
(Solid State Disc) - hard discs. Hereby the charge carriers encode information in a semiconductor.

Most important advantage: there are no mechanical, moveable parts. Thereby, the storage media are
practically producible in every desired form
very fast
Backup of data
Backup of data is mandatory because every storage media may fail and the stored data can irreparably be lost.
We distinguish between three modes:
complete Backup
: the entire database of a memory is saved
differential backup
: the new or modified data are saved after the last complete backup
incremental backup
: the new or modified data are saved after the last backup

Important advice:
use several different backup media
store media in a different place than the data to be saved
well documented backups
test rewinding of a backup
Output devices
Output devices
Concerning output devices, we only deal with color printers.
Here, we consider four printing technologies:
thermal transfer printer
thermal sublimation printer
inkjet printer
laser printer
Thermal transfer printer
thermal transfer printers use a flexible plastic foil as substrate on which the color pigments are brought up in form of a wax layer.
by use of heat in fine needles the wax is molten and transferred onto the paper.
There are separated zones on the foil with cyan, magenta, yellow and black as color material. These "blocks" are successively imprinted.
Then, this results in a subtractive color mixture.
thermal transfer printers are simple, cheap but limited in resolution and color variety.
Thermal sublimation printer
Similar to the thermal transfer printer a substrate with color pigments is used. With this type of printer, however, the material evaporates and then condenses in stable form on the paper. Because the phase transition solid - gaseous - solid exists without the liquid phase, we use the term "sublimation". This gives the type of printer its name.

The advantage of this procedure is that the amount of evaporated material per pressure point can be controlled. With this a flexible mixture can be made in every pressure point by the three basic colors. That is why these printers normally have the best color printout (photographic printer).
Laser printer
Laser printer use a solid powder, the
A color laser printer therefore uses 4 toner: cyan, magenta, yellow and black. The procedure is roughly the following:
a laser exposes the
photosensitive drum
to the parts where the toner powder should stick
by means of a
and a very fine iron powder that is mixed with the toner, the starter, the toner is transferred to the image drum
In the
transfer unit
the toner is transferred from the photosensitive drum on to the paper
by means of
the toner is fixed on the paper
Ink jet printer
Inkjet printers use liquid inks. Mostly 4 (cyan, magenta, yellow, black), sometimes additionally light ink colors. Basically we distinguish between these processes:
drop on demand
" - hereby the ink droplets are generated when they are printed on the paper
continuous drop
" - hereby a continuous flow of droplets is generated and those are deflected that are not needed
The most often used procedure is the first one.
Concerning the print techniques we distinguish between two important variants:
Bubble Jet
By using the
Bubble Jet
procedure a
heating element
generates a small bubble with which the ink is tossed out of the nozzle. So, the used inks need to be

procedure uses a
Piezo crystal
. This one has the characteristic to expand when applying potential. Thereby the pressure increases in the nozzle chamber and the droplet is ejected.
Ink printing technique
Subtractive color mixing
The question is important how mixed colors can be generated because normally only few basic colors (mostly 3 + black) are used.
The answer is: the mixture of color takes place in the eye-brain of the observer. If you bring up different
of the basic colors fine enough, the details cannot be dissolved anymore and we "see" the mixed color.

For the application of diverse color parts there are two basic processes:
procedure - hereby
different big
color circles are printed
procedure - hereby a
different number
of droplets of the same size are printed in the print cell
Example of a 4x4 dithering matrix
Example of a half tone dot pattern
Operating system
The operating system provides the interface between application programs and the computer system, thus the hardware. Furthermore, it offers administrative services. Fundamental components are:
Process Management
File System
Memory Management
Virtual Memory Management
Input/Output Management
Network Services
Interface to System Calls

Software modules that specifically serve as communication with hardware components are called "driver".
Boot Process
" means starting the computer. The difficulty here is that you can get into a sort of vicious circle: on the one side you need the code of the operating system in the main memory - on the other side it is stored on one of the data storage devices (e.g. hard disk) - and eventually there needs to be a running software system in the main memory already so that you have access to the data storage device.

Solution: a specific software - the
BIOS (Basic Input Output System)
- that is available in a specific hardware module, the
ROM (Read Only Memory)
on the motherboard. This software is automatically loaded and run when starting the computer. It is therefore highly hardware-specific.
A very important component of the operating system is the filesystem. It establishes the link between the data storage by the users - typically in form of files that are found in the directories - and the hardware - typically the harddisk.

The smallest physical storage unit is called
512 byte
can normally be saved. Sectors can only be used as a whole. That means they are completely used, even though not all bytes contain data.

In order to decrease the administration effort of the modern, big harddisks, several sectors are combined to a
. A cluster is then the smallest (logical) storage unit and can only be allocated as a whole. Clusters are clearly numbered consecutively.

The fact that clusters can only be allocated as a whole leads to the fact that a bigger space of the harddisk is allocated than actually corresponding to the data volume.
Amount of data and allocated space on the data medium differ
Quite often you want to split a big harddisk into several "
logial harddisks
". These appear as independent drive to the user with its own drive letters, but are contained in a physical drive. These are called

The question now is how the operating system gets the information about the distribution in partitions. This information is saved in the
first sector
of the drive in the so-called
"partition table"

The first sector is called "
Master Boot Record - MBR
". Besides the partition table it contains a software code that is used for starting the system, the so-called "
boot code
". This one also makes the MBR the target for virus attacks.
FAT - File Allocation Table
Basically the question needs to be answered how the system knows which cluster belongs to which file. Due to the
these do not need to follow each other.
The solution lies in the fact that in a table (that is being saved twice) a
is stored for each cluster. The marking can consist of four different values:
(the cluster is not yet allocated)
(the cluster does not save information reliably anymore and may not be used)
("end of file" : this one is the last, final cluster of this file)
number of the next cluster
belonging to the file

The table is called "
file allocation table - FAT
". It comes immediately after the MBR - master boot record.
The term
refers to the fact that clusters of a file do not lie immediately in a row, therefore can be spread among the whole harddisk. The fragmentation is caused by ongoing printing procedures and erasing procedures.

See also my animation:

If the fragmentation is very large, it reduces the speed of the computer. Therefore, the filesystem tries to counteract this by "redistribution" of the cluster. You can also start the process that is called
by yourself.
Root directory
With the help of the saved information in the FAT for the cluster, the information belonging to a file can be found even though the clusters are widely scattered. As a last step you need a "starting point" with the result that the number of the first clusters of a file are known. That is what the
root directory
It has a
fixed size
of maximum 256 entries and is arranged directly behind the FAT.
Files and subdirectories can be compiled in it.
A German animation showing the complete reading operation of a file can be seen here:

The users point of view
From the point of view of the user the information is stored in files that are in turn filed in the directories which are located in the drives.
The combination of drive + directory + file name is unique and is called "path" of a file.

In Windows drives are defined by letters plus a colon, e.g. "c:" or "d:".

Directories are separated by a backslash "\". Whereas, in UNIX and with internet addresses the "/" is used.

The last part of the file name after the last dot is called "extension". It should characterize the type of a file and is used for the automatic start of the assigned applications.
Examples: ".docx" -> WORD; ".pptx" -> Powerpoint
Text processing with WORD
Basic elements of a WORD text:
- there are printable characters and special characters that are used for formatting and control
- separated by space and "-", not by "."
- when a manual line break should be carried out the keystroke combination "SHIFT+RETURN" is applied
- defined by sentence separators (e.g. ".", "!")
- by "Return" key
- either automatic separation by the WORD in continuous text or by "manual page brakes"
- by "manual section breaks"
- entire text saved in one file
Paragraph formatting
The following formattings have paragraphs:
(forced justification)
Change of sections
allow essential scopes for design and structuring of a text document:
different header and footer
(if required also no header/footer)
different formatting of page numbers
(for example Roman numerals)
different page layout
(vertical/horizontal format or margins)
different number of columns
(may also vary within a page)
Character formats
There is a number of formatting possibilities for characters. A selection:
small caps
Tools in WORD
WORD offers several tools. The ones mentioned here:
spelling checker
auto formatting
organizational chart
formula editor
text revision
Spread sheet with EXCEL
Basic element is a cell. It is the intersection of a column and a row.
Columns are addressed with letters: A, B, C ... AA, AB, ... AZ, BA, BB, ...
Rows with numbers: 1, 2, ...
Cells from the combination of column address and row address: A1, B12, BA77, ...

The types of content of a cell can be:
logical value
error value
Operators within equation
Arithmetic operators:
+ : addition
- : subtraction
* : multiplication
/ : division
% : percentage value = value/100
^ : calculation of power

& ("ampersand") : assemble texts (from cells) to an entire text
Operators within equation
Logical operators:
The result is always a logical value (TRUE or FALSE).

Example of an equation:

the equation checks if the value of the cells A2 and C3 are unequal.
Reference operators
Cell references, the addresses of cells or areas of cells, are defined in equations with the following operators:

";" connects cells or areas of cells
":" defines an area by indication of upper left and lower right corner mark
" " defines intersection of two areas

Example of a definition of an area of cells:
= (A1:B3;C1:C4;E5)
Cell addresses
In an equation the cell addresses can be defined in three different ways:
relative (=A5)
absolute (=$A$5)
mixed (=A$5)
For identification the dollar sign ($) is used.

In the cell in which an equation is inserted the addressing mode has no influence, however it has an impact when copying the equation. All address parts having a $ sign in front do not change, all the others change according to the difference of output address and destination address of the copy process.
Thanks to
Rebecca Szekely
for translating my German presentation.

Computer Graphics
Types of Computer Graphics
Fields of Computer Graphics:
pixel based

computer graphics
Raster graphics
basic: image data
vector based
computer graphics
object oriented computer graphics
basic: geometrical objects

We can also distinguish between:
2D graphics
3D graphics
2D vector graphics
Geometrical objects:

P(x,y,z) x,y,z = coordinates of a point (2-dim. z = 0)

, Vertex Connection of two points P1 - P2

sequence of lines between n points P1 - P2 - P3 - ...

closed polygon of 3 points

closed polygon of 4 points

may be defined by: center, point on circumference
center, radius
3 points on circumference

filled rectangles, filled closed polygons, ...
Smooth Curves
Definition of smooth curves by:
polynomials connecting the nodes
piecewise definition
==> Bézier curve
3D Graphics
of a 3D object:
Base area + extrusion
Base area + rotation
Geometrical frame (e.g. sphere)
Closed three-dimensional polygons,
in general triangles or rectangles

3D Surface Display
Shading options:
Flat shading
Gouraud shading
Phong shading
Texture Mapping
The surface of objects may have different materials:
Define surface elements with different properties (color, reflection …)
--> very time consuming regarding modeling and image calculation
Projection of a pattern = texture on the surface of the object
 ==> "Texture – Mapping"

Ray Tracing
Complex scenes with several objects:
Reflected light from objects illuminate other objects
Objects are mirrored in other objects
Light (illumination) is influenced by dust, fog, …

Detailed calculation of physical propagation of light ==> "
ray tracing

Image calculated with ray tracing
3D Animations
Additional challenges in animated scenes:
physical properties of different materials
Interference between objects

Stereoscopic Images
„Real" three dimensional impression:
Different views for both eyes, calculated from different perspectives
Anaglyphic picture (red / cyan glass)
Polarization (Polarization glass – often in cinemas)
Shutter technique (Shutter glass – some monitors)
auto stereoscopic systems (without glass)

Ubiquitous Computing
" describes the already in the mid-eighties predicted development by the scientist Patrick Weiser that computers will become ubiquitous. They are increasingly integrated in everyday objects and the users are permanently connected to the networked computer systems.
Augmented Reality
" describes the blend of pictures of the real environment of the user with virtual contents generated by the computer.
Display of user manuals and tools in the glasses of maintenance engineers (plane, automobile, ...)
Display of tourist information in images of buildings, places etc. on smartphones
Networked computer games that take place in the real environment of the gamers
Virtual Reality
" describes a computer generated environment where as much sensory input as possible is replaced by virtual content.
Ultimately the user is not able to distinguish between real and virtual world (immersion).

Different categories are now available:
Low cost ~ 10 € - e.g. Google cardboard
Medium cost ~ 100 € - e.g. Samsung Gear VR
High cost ~ 1000 € - e.g. Oculus Rift
Professional ~ unlimited - e.g. Cave system

Colour Perception

Reflectivity (of material)
„cells“ (in the eye)
Brain (Psychology)
Physical nature:
electromagnetic waves
characterized by amplitude and wavelength

"normal" light source:
combination of different wavelength with different intensities ==> spectrum

Types of light sources:
continuous spectrum (temperature)
discrete spectrum (atomic process)
Interaction of light with material:

fraction of reflected light is depending on wavelength of light ==> reflectance spektrum
Human eye has 2 different cell types:

Cones exist in 3 variants with slightly different sensitivities in different wavelength spectra. They correspond to colour perception "red", "green" and "blue".
CIE colour model
CIE measured visual perception of humans, specified the spectral sensitivity ==> "standard observer"

These sensitivity values can be used to calculate CIE colour values x,y,Y

Famous: chromaticity diagram
Device Specific Colour Models
RGB values
8 bit ==> 0 - 255
CMYK values
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