Software II

Content of the lesson:

Application Software - Second Part

Security Software

This is software which protects your computer or a computer network from being attacked by viruses or hackers. The most used types are antiviruses and firewalls.

• Antiviruses - In the past these programs were used for removing viruses. Nowadays they focus on finding and defusing viruses in realtime and preventing viruses to get into computer. It uses resident and web shields for this purpose.
  • Examples: AVG, NOD 32, AVAST, Kaspersky
• Firewall - This is special software which controls and manages everything which goes through a computer and its network. It can block attacks aimed directly to a computer. Firewall has to be set properly.
  • Examples: Firewall in Windows, Kerio

Microsoft Security Essential

Archiving Programs

Archiving programs are applications which can compress (encode) data files (text, graphic or binary data) to an archive which is smaller than the size of this data before. Other programs can decompress archives without damaging data of course. Software which can be called as an archiving one has to be able to compress and decompress data at once.

Why to compress data?

• saves space on a hard drive
• saves time when transferring data
• saves potential costs for connection and allows faster transfer of data in a network
• uses logical data sorting according to its type (text, graphics etc.)
• allows to separate the final archive to several smaller files

Types of compression - There are two generally different types of data compression.

• Lossless compression - This principle is used when you cannot afford any data lost. It is used for text or binary data (executable files *.exe etc.). In case that one bit was lost, it would mean a disaster because you would not be able to use that file anymore.
• Loss compression - However, there are several types of files which can be compressed with losses. These files are called redundant files - files with superfluous amount of information. Especially images, sound files and video sequences belong to this category. Because of imperfections of human sight and hearing two things can appear to be identical although they do not contain the same amount of information - the numbers of bits differ. We talk about loss compressions in connection with files like JPEG, MP3, WMA etc.

The main parameters of performance of archiving algorithms:

• speed of compression
• speed of decompression
• compress ratio

The most used archiving programs:

• WinRAR, WinZip, 7-Zip, UltimateZip, FilZip

SW Reviews

• functionality and variability
• throughput – amount of data and number of operations which can be done in an unit of time. It depends also on the parameters of technical equipment
• reliability – how the required functions are done, resistance against user mistakes or equipment faults
• response time – depends also on the technical equipment
• demands on control – especially if the program is user friendly
• level of documentation – range, clarity, clearness
• adaptability – ability to react on changes in functionality
• portability – ability to move the software to a computer of another type or made by another manufacturer
• price – this item is a large part of the price of whole computing system

Lifecycle of SW

• specification of a problem – assignment of a problem, draft of communication with program
• analysis – creating a logical model of the current problem
• draft – decomposition of single problems, drafts of methods to solve them
• implementation – draft of data representation, design of algorithms, notation in a programming language, debugging
• creating documentation – users have to be able to use the program easily
• testing – checking whether the program is running correctly
• service and maintenance – removing detected problems and adapting the program to additional requests

„Computer does only what we have programmed, not what we want.“

Dividing SW According to Type of Distribution - Licenses

• Public domain - programs can be used without paying, the author gave his copyright out (you even do not have to tell his name), but be aware not to confuse it with freeware license
• Freeware - you can use programs without paying (but not change them), author has his copyright, there is also a limited freeware, so called freeware for non-commercial use – such a program can be used without paying for non-commercial purposes.
• Shareware - programs can be copied or distributed, you have to pay a registration fee and register yourself
• Adware - programs are free of charge but an advertisement is displayed inside - the development is paid from this advertisement. You cannot remove advertisement because you would violate the license. The advertisement is usually downloaded from the Internet.
• Donationware - you can pay if you want, but the fee is optional
• Open source - you do not have to pay for this software, also its source code is available, protected under the GNU GPL license, novella LGPL (Linux, GIMP, OpenOffice)
• Full version - full program, all functions are available without limits
• Commercial programs - program is distributed after payment, copyright is used
• Demo version - this program only illustrates the possibilities of the product, the functionality is limited using any way, for example you cannot save, display or process the result
• Trial version - usually full version of a product which is limited to a particular time period or to a number or launches. This license is used to allow users to try the program and its functions before buying the full version
• OEM software - these programs are distributed only with hardware, it is a normal version of program but the price is usually reduced

Free Software

GNU General Public License

Free software is a program which was released with its source code and with the rights to use, edit, sell or give its copies or its adjusted versions. The most of these programs are free of charge but it is not a condition.

The project GNU was founded in 1984 and it has defined 4 freedoms:

• freedom to use the program for any purpose
• freedom to study how the program works and to adapt it to different requests
• freedom to redistribute any copy of the program - so called Copyleft license (the original or changed version of program has to be distributed under the same license as the previous program)
• freedom to improve the program and publish these improvements which can be used by the whole community

Free software does not mean non-commercial. A free program has to be available for commercial usage. A commercial development of a free program is nothing unusual, those programs are then commercial free programs.

Attention: There is no warranty on products distributed under GPL unlike the other products.

Copyright

• protects each work (artistic, technical and software)
• license arrangements
  • contract between the owner of copyright and a user
  • sets the conditions of installing and using SW
• license violation
  • using unauthorized number of licenses
  • using unlicensed SW
  • copying SW for commercial purposes
  • crime

Individual Task

1. Try to compress different data and observe the changes of size in each case.
2. Search for examples of software for each category of licenses.
3. Find which sanctions can be given when violating copyright.

Questions

1. What is the purpose of security software? Which types do you know?
2. What is archiving and which advantages does it bring?
3. How can we divide software according to licenses? Name and describe several licenses.
4. What is free software?
5. How is the copyright connected to software?