Lecture 1: .NET

1. Lecture 1: .NET What Is It And Why Use It? .NET - What and Why

2. Software from Components • In the industrial revolution, engineers learned to build things in a consistent, predictable, repeatable way • Design once, build many identical parts • They learned to use assembly lines to assemble multiple items from sets of identical components • Any component of a given type and specification is interchangeable with another of the same type .NET - What and Why

3. Why not build software the same way? • Multiple languages and incompatibilities • Basic, C, C++, COBOL, Visual Basic, C#, F#, Java, Fortran, Perl, Python, Eiffel, Delphi, SQL, Pascal, PL/I, APL, assembly, Scheme, Smalltalk, Prolog, Lisp, RPG, Ada, Snobol, Forth, Algol, Modula-2, HTML, Haskell, JavaScript, Objective C, ABAP, … • Cannot just take a block of code from a Lisp program, for example, and plug it into a COBOL program and expect it to work • Usually, cannot easily call an Ada method from a Python program, for example .NET - What and Why

4. Why not build software the same way? • Different Data Types • Many different data types • Not implemented the same way in all languages • Implementations vary in size • Character type may take 1 byte (ASCII or EBCDIC) or 2 or more bytes for Unicode • Integers may occupy 8 bits, 16 bits, 32 bits, 64 bits, 128 bits, . . . .NET - What and Why

5. Why not build software the same way? • Different conventions • Argument passing may be left-to-right or right-to-left • Arguments in one language may be passed using a stack; others use registers, pointers, or someothermeans; not consistent among languages • Name collisions • Same term may be used differently in different languages – a classname in one language may be a keyword in another .NET - What and Why

6. Why not build software the same way? • Different platforms and architectures • Addresses and data: 16-bit, 32-bit, 64-bit,… • Big-endian (ABCD) vs. little-endian (DCBA) • Different instructionsets • Differences in registerarchitecture .NET - What and Why

7. Why not build software the same way? • Different operating systems even on the same hardware • Almost all user software depends on and uses services provided by the OS and its subsystems • Different OperatingSystems have different ways of implementing the services, different API’s, different conventions, different security approaches, different levels of support for various activities .NET - What and Why

8. Why not build software the same way? • Different Human Languages; Different Cultures • English, French, Japanese, Chinese, German, Spanish, Arabic, Russian, Hebrew, … • In the US, 1.23 represents 1 and 23 hundredths, while in many European cultures, the same value would be represented as 1,23 • Fahrenheit vs. Celsius; in US,30 degrees is cold while in Canada,30 degrees is hot • US Dollars vs. Canadian Dollars, Euros, Yen, Rubles, Riyals, Dirhams, Pesos, Yuan, ... • Dates: 03/04/2014 is March 4, 2014 in the US, but it is April 3, 2014 in much of Europe • Inches, miles, gallons, pounds vs. centimeters, kilometers, liters, and kilograms . . . .NET - What and Why

9. COM, CORBA, Enterprise Java Beans • Various companies and groups of companies came up with approaches that could be used to standardize things and allow components to work together • Problems: • All approaches were proprietary • Approaches incompatible with each other • Not based on open standards .NET - What and Why

10. .NET • Based on a standard developed by Microsoft, Intel, IBM, and others • Approved as a standard by ECMA • Approved as a standard by ISO • Standards cover CTS, CLS, C#, and other items • Designed to be languageagnostic • Platformneutral • Open to development by anyone .NET - What and Why

11. Many others including IronPython, IronRuby, Cobol, Delphi, JavaScript, etc. The virtual machine runs this .NET - What and Why

12. Common Type System (CTS) • All .NET languages support common types – though not necessarily using the same names • System.Int32 is called int in C++ and in C#, and Integer in VB, but they are same type and can be passed back and forth as arguments • System.Single is called Single in VB and float in C++ and C#, but all are the same type and are interchangeable in the .NETlanguages .NET - What and Why

13. Common Language Runtime (CLR) • All .NET compilers emit platform-neutralIntermediate Language (IL) object code (like byte-code in Java) rather than native machine language code • IL is the same regardless of hardware, OS, or .NETlanguage • Output of a project is called an Assembly: may be either a .EXE or a .DLL • Only the CLR needs to know on what platform it is running .NET - What and Why

14. CLR, continued • CLR contains a Just-In-Time (JIT) compiler that turns IL into nativemachinelanguageoptimized for its targetmachine • Very fast and efficient • Done only once and only if needed • Thus code is compiled, not interpreted as in some languages • CLR also handles garbage-collection, exceptionhandling, cross-language debugging, and distributeddebugging, and other common features • Includes runtimesupport for thousands of .NETclasses .NET - What and Why

15. IL Example .method public hidebysig static void Main() cil managed { .entrypoint .custom instance void [mscorlib]System.STAThreadAttribute::.ctor() = Code size 14 (0xe) .maxstack 8 IL_0000: nop IL_0001: newobj instance void ManageDB.frmTblMgmt::.ctor() IL_0006: call void [System.Windows.Forms]System.Windows.Forms.Application::Run(class [System.Windows.Forms]System.Windows.Forms.Form) IL_000b: nop IL_000c: nop IL_000d: ret } // end of method frmTblMgmt::Main .NET - What and Why

16. Which language? VB.NET compiler MSIL C# Compiler JIT compiler Runtime Compilation and Execution Form1 C# code Visual Basic .NET code CLR Nativecode .NET - What and Why

17. Platform Neutral • Because the IL code is not targeted at any platform, it is portable between systems of different HW, SW, etc. • A (.NET) .exe and a (.NET) .dll compiled on a Windows system will run on a Mac, a Sun, or an IBMmainframe . . . IF. . . the target machine has its ownCLR with a JIT compiler to convert the IL code to nativecode targeted to the machine on which it is to run and to provide the runtime support for the .NET classes .NET - What and Why

18. Language Interoperability • The standards that are part of .NET insure that: • A Windows control developed in VB.NET can be used in a C# program • A method written in a business-tierclass in COBOL.NET can be invoked by a VB.NETWindowsForms front end • A .NETstring in a Delphi.NET program compiled using a Borland compiler on a Windows computer can be passed to a C# method written using a SSCLI compiler running on an Apple OS-X platform .NET - What and Why

19. .NET Implementations • Implementations of .NET include • Microsoft’s .NETFramework and Visual Studio.NET • The SharedSourceCommonLanguageInitiative (SSCLI) that runs on BSDUnix and AppleOS-X • Mono - opensource effort up until recently led by Novell and others • More than 30 languages support .NET: • Microsoft: VB.NET, C#, managed C++, Cω, Spec#, F# • Python, Perl, Cobol, Delphi, Pascal, Eiffel, Fortran, RPG, Scheme, Smalltalk, Ruby, Forth, and many others by non-Microsoft vendors • Thousands of tools are available from third-party vendors to aid in .NET Framework development, including more than 1000 add-ins for VisualStudio.NET, as well as compilers with their own IDE’s from Borland and Macromedia .NET - What and Why

20. Thus, … • Solutions/Applications can be developed in any .NETlanguage or languages (by project) that fully supports the features used by the application and that adheres to the standards • Differentparts of the application (solution) can be developed in differentlanguages • A VB main program can use a class developed in C# that uses another class developed in F#, for example • In a .NET web application, each web page at a web site could be developed in a separate .NET language .NET - What and Why