ict project
DESCRIPTION
Information and Communications TechnologyTRANSCRIPT
• Program
Expressions
Operators ConstantsVariables
Hierarchy Data Types
Names
Numeric Non-Numeric
Integer
Long
Currency
Single
DoubleVariant
Date
String
Boolean
Objects and Basic Codes
• Objects are combination of codes and data that Visual Basic considers as single units.
• Forms, Command Buttons, Labels, etc. are examples of objects in Visual Basic
Objects and Basic Codes
• Each has a different set of properties that you can modify. For instance, all objects have the property, which tells you the name of the object, or how the computer identifies it. But only the dropdown List Box has the property List, which gives you the file source from which it gets its options.
Property Types of an Object
• You can choose to modify the properties of an object to change its look in your program. They can be classified into six types, based on how you can edit these properties.
Boolean Value Property
• This property type is set to options that are answerable only by true of false.
• Examples: Enabled, Visible, Multiline, Moveable, AutoRedraw, and Clip Controls.
Predefined Value Property
• This property type consists of choices with-in the drop-down list box with a corresponding value and function.
• Examples: Appearance, BorderStyle, Value, Alignment, MousePointer, andBackStyle
String Value Property
• This property type allows you to encode new data.
• Examples: (Name), Caption, PasswordChar, Text, Index, and Tag
Hexadecimal Value Property
• This property is set to color options.
• Examples: BackColor, ForeColor, FillColor, MaskColor, and BorderColor
Filename Property
• This property type allows you to import a file or files.
• Examples: Icon, Picture, Font, MouseIcon, Palette, and DataFormat.
Size Property
• This property type allows you to set the new size of an object.
• Examples: Height, ScaleWidth, Width, ScaleTop, DrawWidth, and ScaleHeight.
Events
• An event is a message that is sent out by an object announcing that something has happened.
• When a user does a certain action to an object in a Visual Basic program, the computer responds with an appropriate output based on what the function of the object is.
Events
• To signal this output in your program, you must write (in code) an event procedure that is associated with an object.
Parts of a Visual Basic Statement
• The Visual Basic program statement is a line of code that consists of the object name, property, and value.ObjectName.Property = Value
Parts of a Visual Basic Statement
• Object Name refers to the object’s assigned name in the project.
• Property refers to the associated property to be edited or changed in a object.
• Value is the assigned value for the corresponding property.
• The equal sign is used to assign an item; it may be a number or a string.
Form1.BackColor = vbBlue
Object Name Property Value
The statement above involves changing the appearance of a form, which is Form1. Its background color (BackColor) is to be changed to blue (vbBlue).
Software Piracy
• Software piracy refers to the unauthorized duplication and use of computer software.
Basic Software Piracy Terminology:
• Cloning - Ideas can not be copy protected, and unfortunately some software developers choose to "clone" other applications rather than creating their own.
• Crack - A software crack is an illegally obtained but working version of the software, which circumvents the software's copyright protection. Software cracking refers to the modification of software in order to remove encoded copy prevention. Distribution of cracked software is generally an illegal act of copyright infringement.
• Cracker - An individual that undertakes disabling software protection, either for fun or financial gain.
• Hack - The classic and somewhat innocent definition of hack used to be just "a clever workaround". The term now has a much more negative connotation, and usually refers to working around the copy protection of an application for the sole purpose of creating an illegal version of the software. While not always the case, a hack could be a fix, or a bug workaround.
• Hacker - One who hacks. The original definition was "a clever programmer", but the term has since come to mean someone who tries to break into computer systems or protected software.
• Hardware Locking - A method of protecting software from duplication by locking the software license to a specific piece of computer hardware, such as the hard drive it is installed on, so that it will not function on any other computer.
• KeyGen Or Key Generators - a KeyGen (short for Key Generator) is a small program that will generate an unauthorized but working registration key or serial number for a piece of software. It is typically used to circumvent copy protection and create an illegal version of a software application.
• Serials - Usually refers to illegally obtained registration keys or "serial" numbers that unlock a downloadable evaluation version of a product.
• Warez - Another term for a software crack.
Types Of Software Piracy
1. It is illegal to use a single-licensed version on multiple computers.
2. It is illegal to preloaded software on computers without providing the appropriate licenses.
3. It is illegal to use a key generator to generate a registration key that turns an evaluation version into a licensed version.
4. It is illegal to use a stolen credit card to fraudulently purchase a software license.
5. It is illegal to post a licensed version of a software product on the Internet and make it available for downloading.
In determining whether the use made of a work in any particular case is fair use, the factors to be considered shall include:
(a) The purpose and character of the use, including whether such use is of a commercial nature or is for non-profit educational purposes;
(b) The nature of the copyrighted work;(c) The amount and substantiality of the portion used in relation to the copyrighted work as a whole; and
(d) The effect of the use upon the potential market for or value of the copyrighted work.
Arithmetic Operators
• Are used to indicate operations such as addition, subtraction, division, multiplication, exponentiation, integer division, integer remainder and modulus.
• These operators are used to connect number constants an nonnumeric variables to form arithmetic expressions
Visual Basic Operation
Operator Example Answer
Exponentiation ^ 3^2 9
Negation - 3-2 1
Multiplication/ Division
* Or / 3*2 or 3/2 6 or 1.5
Integer Division \ 3\2 1
Modulus Mod 3Mod2 1
Addition/ Subtraction
+ or - 3+2 or 3-2 5 Or 1
What is a Variable?
• A variable refrences a memory location which can contain any type of data. And the size of the emmory allocates depends on the type of data stored in it.
Naming Variables
• A variable must begin with a letter of the English alphabet
• The reserved words or code words can’t be used as variable names (e.g. Then, For, Len, Case, End, Mid, etc)
• A variable name should not exceed 255 letters and can only use letters, numbers, and the underscore character
• Spacing in variable names is invalid (e.g. Your School, Full Name, etc...)
Constants
• It is a value that cannot and should not be altered by the program and is a set value for a certain data within a program.
• These are declared indifferently
Numeric and Nonnumeric Variable Types
• Numeric Variables are variables that can be mathematically manipulated
• These are expressed as Integer, Long, Single, Double, and Currency
• Nonnumeric Variables are variables that can’t be mathematically manipulated
• These are expressed as String, Boolean, Date, and Variant
Data Type Range Size Example
Integer -32 768 to 32 767 2 Bytes 32 766
Long -2 147 483 648 to 2 147 483 647
2 Bytes 32769
Single For negative numbers:-3.402 823 ^38 to -1.401
298^-45
For Positive Numbers1.401 298^-45 to 3.402
824^38
4 Bytes 0.000 005
Double For negative numbers:-1.797 693 134 862
326^308 to -4.940 656 458 412 47^-324
For Positive Numbers1.797 693 134 862
326^308 to 4.940 656 458 412 47^-324
8 Bytes 0.000 000 000 05
Currency -922 337 203 685 477.5808 to 922 337 203
685 477.5807
8 Bytes 1 002 500.5796
String 1 to 65 535 characters 1 Byte per
character
Hello World
Data Type Range Size Example
Boolean True or False 2 Bytes True
Date Jan 1, 100 to December 31, 9999
8 Bytes 4-12-2000
Variant All data types except fixed-length string data
16 Bytes
“Hello World”
Variable suffixes in Visual Basic
Data Type Suffix Example
Integer % Dim X%X%=32766
Long & Dim X&X&=32769
Single ! Dim X!X!=0.000005
Double # Dim X#X#=0.00000000005
Currency @ Dim X@X@=1002500.5795
String $ Dim X$X$=“Hello World”
Strings and Concatenation
• Used to represent nonnumeric information such as gender, status, name, address, and the like. They are always entered in code inside quotation marks.
• String Concatenation is the process of combining two or more strings into one single string. You can se either the ampersand (&) or the plus sign (+)
• e.g. Word1=“hello” Word1 & ”” & Word2
Word2=‘world” hello world
Commonly Used Library Functions in String Variables
Function Application Definition Example
Len Z=Len(Word) Displays the length or number of characters of the string Word
Word=“Programming”Z=Len(Word)Print ZOutput:11
Lcase Z=LCase(Word)
Displays the lowercase equivalent of the string Word
Word=“Programming”Z=LCase(Word)Print ZOutput:Programming
Ucase Z=UCase(Word)
Displays the uppercase equivalent of the string Word
Word=“Programming”Z=UCase(Word)Print ZOutput:PROGRAMMING
Commonly Used Library Functions in String Variables
Function
Application Definition Example
Left Z=Left(Word) Used to extract the rightmost x characters of the string Word
Word=“Programming”Z=Left(Word, 4)Print ZOutput:Prog
Right Z=Right(Word)
Used to extract the rightmost x characters of the string Word
Word=“Programming”Z=Right(Word, 8)Print ZOutput:gramming
Mid Z=Mid(Word) Used to extract x2 characters from the middle of the string Word, beginning with the character number x1.
Word=“Programming”Z=Mid(Word, 4,4)Print ZOutput:gram
Computer Virus
• A computer is a program maliciously written with the intention of entering a computer system without the user’s permission or knowledge. Such codes hide in computer programs or on the boot sector of storage devices such as hard-disk drives and other portable storage devices. A virus has the ability to replicate itself and may affect other programs or system performance.
Types of Viruses
• There is a variety of computer viruses. Computer viruses can be classified according to the techniques, types of files they infect, where they hide, or the kind of damage they cause. Some of these viruses are classified as follows:
Personal Digital Assistants (PDA) Viruses
• As the development of technology on PDAs continues, new breeds of viruses have spawned. Malicious programmers have taken advantage of the PDA’s ability to communicate. With other devices and run programs.
Boot Sector Viruses
• These types of viruses infect the DOS boot sector or the Master Boot Record of a PC. Infection is done by substituting their code, thus overwriting it. The MBR is a small program that runs every time the computer starts up. Therefore, when the computer loads the operating system through infected boot records, the viruses also load into the memory. From the memory, the boot viruses can spread to every disk that the system reads.
Macro Viruses
• A virus that is created by using a built-in macro programming language, designed to execute as soon as the file is opened. It attaches itself to a document file and waits until an application like MS Word or MS Excel opens it.
Worms
• These are computer programs that are characterized by their ability to copy themselves from machine to machine. They are deigned to self-replicate and spread without any user influence. When a file that contains a worm is opened, it starts spreading through networks and emails immediately. The main purpose of a worm attack is to bring down systems and networks by consuming great amounts of bandwidth and memory.
Trojan Horses
• These programs disguise themselves as legitimate programs such as game or utility. Trojan horse programs often look and initially act like legitimate programs, but once they are executed, they can destroy or scramble data. Different from other viruses, Trojans do not replicate themselves as fast as viruses do.
Bombs• These are pieces of code intentionally inserted into a software that will set off a malicious function when specified conditions are met. Such conditions Can either be logical or timed. Malicious software often contains bombs that execute a certain payload. Many viruses attack their host system on specific dates, thus called “time bombs.”