2015-11-08 - In IL: Introduction

In IL

• Part 1 - Introduction
• Part 2 - Variables and Types
• Part 3 - Variables in Visual Basic .NET
• Part 4 - Instructions and the Stack
• Part 5 - Volume of a Cylinder (Operations)
• Part 6 - Branching Instructions
• Part 7 - Largest of Two Numbers (if-else)
• Part 8 - Largest of Three Numbers (If-ElseIf-Else)
• Part 9 - Switch instruction
• Part 10 - Grade Analyser (switch)
• Part 11 - Prize Calculator (switch-2)
• Part 12 - VB Grade Analyser (Select)
• Part 13 - Loop Instructions
• Part 14 - Print the Alphabet (while)
• Part 15 - Print the Alphabet (do while, for)
• Part 16 - Print the Alphabet (Do Until)
• Part 17 - Print the Alphabet (break, continue)
• Part 18 - Array Instructions
• Part 19 - Summing Arrays
• Part 20 - Other Instructions
• Part 21 - Assemblies
• Part 22 - Class Definitions
• Part 23 - C# Classes and Structs
• Part 24 - VB Classes, Modules and Structures
• Part 25 - Field Definitions
• Part 26 - Field Declarations

The Common Intermediate Language (CIL), Microsoft Intermediate Language (MSIL) or usually just Intermediate Language (IL) is the language of the virtual machine component of the Common Language Infrastructure (CLI) standard. The .NET Framework and Mono are implantations of this standard.

The virtual machine is a lot like a computer but implemented in software. The virtual machine exectures IL programs by compiling it into native code. That native code is the language of the computer that the program is running on and represents the operations that it understands. The virtual machine also handles a lot of tasks that would normally need to be done by the program itself such as allocating and freeing memory. This simplifies programming and also provides isolation between the program and the actual computer.

IL provides an intermediate step between the higher level languages and the native code of the computer. It provides classes and functions which are common in high level languages while at the same time having a syntax and structure more like native code. This makes it familiar to people approaching it from the higher level language point of view and from the native code point of view allowing both sides to easily work with it. It also separates responsibilities because the language designers only need to focus on the IL compiler while the designers of the virtual machine implementation focus on translating the IL into native code. Any changes to the IL compiler benefit all implementations it supports. Any improvements to the virtual machine benefit all the languages that target it.

In this series of posts I want to investigate how languages that target the .NET Framework (C#, Visual Basic .NET) compile into IL code. The idea is to learn a little bit about IL, how the compiler works, and how .NET programs actually run. This information should be useful when designing or debugging programs and may even lead to some ideas about how to build a compiler.

Should be fun.