A computer program is a list of instructions that tell the computer what to do.
A program, like any system, can be seen as sequence of
Input → Process → Output
The Hello World program is the common first program used to introduce
a programming language, it has the objectives of
Verifying that someone is able to properly run a program
Verifying that a program is able to send output to the user
Verifying that someone is able to enter the source code (program statements)
of a program.
C# is more or a compiled program than an interpreted language, which means that
C# source programs must be compiled before thay can be executed (run).
See The Mono-Project. Where C# source file is compiled into
a byte-code-like structure which is then run through a just-in-time compiler. This is similar to how
Java operates.
Creating C# Programs
Most progams will be entered into a file using a text editor, where the programs
can be stored, edited as needed, and reused.
Create a text file named helloWorld.cs
and enter the following program
using System;
class Program
{
static void Main() {
Console.WriteLine("Hello World!");
} // end Main
} // end Program
Example: With the program saved, The compiler can be invoked to compile HelloWorld.cs
into a file main.exe using a command such as : mcs HelloWorld.cs -out:main.exe
Example: The main program can be executed from a command line such as mono main.exe Hello World!
Explanation:
The mcs HelloWorld.cs -out:main.exe command starts the C# compiler, which will
read in the input file HelloWorld.cs file and generate file main.exe.
The mono main.exe command will execute the compiled program.
the program main.exe program sends the output
Hello World! and then terminates.
Note: When using an integrated development environment you will have
menus or buttons that will be able to compile and execute your programs. The actual
commands that will be used may be hidden from you.