Introducing the Common Language Runtime for NET The Common Language Runtime The Common Language Runtime CLR Execution engine of The NET Framework Offers many system services Similar to an OS Runs on a host OS The NET Framework New platform by Microsoft Designed to target the Internet The Purpose of the CLR Safe binary execution Security memory protection Running un trusted code locally Performance and Functionality Native execution JIT Compiled No Sandbox The Purpose of the CLR Bug reduction More code interacting bugs affect more users Ease of integration Developer investment Reuse skills from project to project even if the projects are vastly different Managed Code and the CLR The Common Language Runtime CLR is a runtime engine Manages NET Code such as C applications Provides features such as memory management thread management object type safety security etc Is a part of the NET Framework The CLR and Managed Code Managed Executable Legacy Software unmanaged code Reusable Managed Components Common Language Runtime JIT compilation memory management etc Windows or other operating oystem What is Managed Code Code that targets the CLR C VB NET PERL Java C Cobol etc All Managed code has all features of CLR Object oriented infrastructure Internet oriented infrastructure Access to the Framework Class Library FCL All Managed executables consist of Intermediate Language IL instructions Metadata IL and Metadata MSIL microsoft intermediate language IL CPU independent machine language Just in time compiled at runtime Makes cross language integration possible Metadata Structured information describes programming constructs including Classes definitions field and method definitions parameter lists return types etc ILDasm exe Use ILDasm exe to view IL for managed executable Just in Time Compiling All managed code runs in native machine language All managed code is made up of IL and metadata The CLR JIT compiles the IL and metadata At execution time Executed directly by CPU Allows for the best of both worlds Code management features Performance of full speed execution Executing a Managed Application SomeSources exe Metadata IL At execution time the IL and Metadata are JIT compiled Running Process Memory JIT Compiler Native Machine Language 10010100 10110000 10000000 10111010 11011011 11010111 11000010 01110110 The CPU executes the JITcompiled machine code directly Automatic Memory Management The CLR manages memory for managed code All allocations of objects and buffers made from a Managed Heap Unused objects and buffers are cleaned up automatically through Garbage Collection Some common software bugs are not possible with managed code Leaked memory or objects References to freed or non existent objects Reading of uninitialized variables Impossible to gain access to memory with object reference The Managed Heap Reduces bugs Makes code access security possible No direct memory access Makes type safety possible Incompatible type coercion not possible Performance Newing up objects is much faster than malloc Garbage collection can be a perf hit Garbage Collection Garbage collection occurs when a new operation fails due to lack of memory All managed threads are stopped Collection starts with roots and recursively finds referenced objects Roots globals locals cpu registers Referenced objects are moved down in the managed heap Making space available at the end Removing unreachable objects No Fragmentation References fixed up and managed threads restarted Garbage Collection class MyClass void Method Variable v1 Variable v2 The Managed Heap B do Objects A and D will be cleaned up because neither is directly or indirectly referenced by code A E C Object or buffer in memory D CLR Summary The platform for managed code C VB NET etc Features Memory management security management reflection type safety IL metadata JIT compilation Assemblies managed modules Understanding the platform will make coding NET code easier C VB NET etc