1. C# and the .NET Framework
An Introduction to C#

2. Introduction to Computing
Processors have different instruction sets with low-level simple instructions
High-level languages – more expressive, closer to software design
Compilers translate from one language to another
Interpreters execute code

3. Translating a high-level program
Processor
ABC program
(executable)
Compiler
Translating a high-level program

4. The .NET Framework Two main parts
Common Language Runtime (CLR) manages execution of code and provides services
.NET Framework Class Library provides a large and very useful set of types

5. The Common Language Runtime
Common Type System defines the types of data that manages code can use.
Common Language Specification (CLS) defines features that every language for developing managed code must provide
Each language code compiles to MSIL, Microsoft Intermediate Language. Compiles to native code at runtime.

6. The .NET Framework Class Library
Groups types into namespaces. Contains about 100 namespaces. For example,
System -- Contains fundamental types.
System.Drawing -- Provides graphics.
System.Windows.Forms --
For user interfaces in Windows-based applications

7. C# Features
Object-oriented – used for business objects or system applications – internet applications
Goals include
productivity and safety
power, expressiveness, and flexibility
Combines rapid application development of Visual Basic with power of C++

8. How C# works
Compiler translates C# source to MSIL code for a virtual machine, similar to a hardware processor
During runtime the CLR use a Just-In-Time (JIT) compiler to translate the MSIL code to the instruction set of the processor

9. Compiling and executing a Java program
JIT1
C#Source Code
MSIL
code
Processor 1 code
Compiler
JIT2
Processor 2 code
Compiling and executing a Java program

10. public class Square {
static void Main() {
int number = 345; // '=' denotes assignment
int squared = number * number;
// '*' denotes multiplication
System.Console.WriteLine
("The square of {0} is {1}", number, squared); }

11. The output of Example 1 The square of 345 is 119025
System namespace, Console class, WriteLine method
"The square of {0} is {1}" is a pattern
The value of number substitutes for {0}
The value of squared substitutes for {1}

12. Lexical Structure
Rules for dividing program text into a sequence of elements
Whitespace -- spaces, tabs, carriage returns
Comment – for human readers only
Punctuators ( ) { } [ ] ; , . :
Operators * / and so on
Literals – specific values such as 345
Identifiers – the names used for program entities
Keywords – reserved names for special uses

13. C# compiler lexical analyzer
int number = 345;
C# compiler lexical analyzer
keyword identifier operator literal punctuator
(int) (number) (=) (345) (;)
(whitespace and comment discarded)
Lexical analysis of a single line of Example 1

14. Syntax Grammatical rules for combining lexical elements into programs
Declaration – defines a part of a program
Statements – controls execution sequence
Expressions – compute values

15. The overall syntactic structure of Example 1.1
class declaration
method declaration
statement
statement
statement
The overall syntactic structure of Example 1.1

16. The Steps of Software Development
Identifying the requirements of the system.
Designing a system that meets the requirements.
Implementing the system.
Testing that the system operates correctly and meets the requirements.
Making improvements as needed.