1. CIS 338: Computer Languages & Visual Basic.NET
Dr. Ralph D. Westfall
October, 2011

2. What is Programming? program = list of steps for computer
like a recipe
steps can be in different "languages"
Java, Visual Basic, C++, etc.
each language has own syntax (rules)
like grammars in human languages
“We ain't got no badges” (video; Wikip.)

3. Why Is Programming Hard?
a computer is very "stupid"
it doesn't understand anything: you have to tell it exactly what to do
have to follow all the rules (syntax) of the language as you are telling it what to do
it takes a lot of practice to be able to tell the computer exactly what to do, in perfect syntax ["Simon says:"]

4. Computer Language Types
differences based on:
low level vs. high level
compiled vs. interpreted
special purpose vs. general purpose
procedural vs. object-oriented
functional vs. imperative

5. Language Levels low level: machine language high level
language that a computer understands
binary numbers e.g.,
or hex numbers e.g., a(=10), f(=15)
demo: d, u [decimal address], q
high level
languages that people can understand
words like "if," "else," "for," "true"

6. Language Levels - 2 1st generation : machine language
BFB (hex from DOS debugger)
2nd generation: assembler
MOV DI,96B6
3rd generation: COBOL, FORTRAN, C
4th generation (“4GL,” usually used with databases): NOMAD (advertising hype)
5th generation? (Japanese artificial intelligence research project in ’80s)

7. Translation
need to convert high level languages into a computer's machine language
compiled
all source code in a file converted into an object code file, then run by computer
interpreted
source code converted and run one line at a time

8. Translation - 2
some languages are both compiled and interpreted (e.g., VB 6)
1st compiled into "intermediate language" (like machine language)
.NET languages (~60 groups, Iron) compile into MSIL (Microsoft Intermediate Language) cf. Java bytecode
intermediate language then interpreted and executed by "run time" code (CLR)

9. Translation - 3 some interpreted languages can also be compiled
previous versions of Visual Basic were interpreted languages
interpreter used to run when developing
but distributed as a compiled EXE

10. Managed Code Managed code executes through a virtual machine
“unmanaged code … is executed directly by the computer's CPU” (Wikipedia used to say that)
Java and .NET are based on managed code
Advantages
easier to work with
better security

11. Special Purpose Languages
don't do everything
do a few things very well
example: markup languages
HTML, XML
display text, images, etc.
do NOT do any calculations
example: SQL for databases

12. General Purpose Languages
can be used many different kinds of applications
FORTRAN: mathematical (and other)
COBOL: business/accounting (and other)
BASIC (before VB): an introductory language
Pascal: to teach good programming

13. Procedural Languages one step after another
C, COBOL, BASIC (not VB.NET)
data and actions (procedures) are separated
example: plans for a large wedding
data = list of all food & supplies
procedures = all instructions for every part of the wedding

14. Object-Oriented Languages
newer approach to programming
C++, Java, VB.NET
data and procedures that use it are together in the same place (in an object or a class)
objects can operate independently
event-driven programs
instead of one step after another

15. Object-Oriented Languages - 2
objects
are like things in real world(?)
e.g., car, cat, college
have data (properties) & actions (methods)
is a number an object?
has a (single) value, but has numerous operations (things you can do with it)
can you think of examples of operations on numbers?

16. Object-Oriented Languages - 3
encapsulation or "data hiding"
can only access data through an object's procedures
object is a "black box"
VB.NET provides objects with encapsulated data
e.g., to connect to a database
can create your own classes in VB.NET and then instantiate objects from them

17. Object-Oriented Languages - 4
inheritance: new objects extend capabilities of parents
HourlyEmployee inherits all properties and methods of Employee object
VB used to be “the only ‘object-oriented language’ with no inheritance” (Bruce McKinney)
VB.NET is a true object oriented language

18. Object-Oriented Advantages
objects are easier to understand ("everyone says")
things in real world work like objects
different objects can hook together
like a digital Lego block system
objects can be reused
instead of "re-inventing the wheel"

19. Functional vs. Imperative
most common languages are imperative
"side effects" can make code not run the same when other parts of the system differ
functional programming languages should have fewer bugs
Haskell and Erlang (used in telecommunications) are functional
VB not but see VB Functional Programming

20. Visual Programming
the Visual Studio.NET IDE is a visual environment, not a language
multiple windows:
program code
properties
debugging: locals and immediate
manipulation capabilities
drag and drop controls

21. VB 6 as a Language
commonly referred to as a visual programming language
but visual programming really means selecting symbols instead of writing words
like creating a query in MS Access
falls somewhere in between a 3rd and 4th generation language
object based, not object oriented

22. VB.NET as a Language also somewhere in between 3rd and 4th generation
a truly object-oriented programming language
has many features that are not in VB 6
copied from Java?
inheritance, try/catch blocks, file output streams, etc.

23. Comparison with C# Top 10 reasons VB.NET better than C#
fewer data casts and conversions
better Intellisense (autocompletion)
optional parameters in subroutines
With..End With construct
event handlers require less coding
less typing

24. Test Your Understanding
Visual Basic.NET is:
low level or high level?
compiled or interpreted or ... ?
managed or unmanaged code?
special purpose or general purpose?
object oriented or ... ?
functional or imperative?