A Simple Program
// Hello!
using System;
class Welcome
{
static void Main()
{
Console.WriteLine("Welcome to PCP!");
}
}
/*
This is a multi-line
comment
*/
Only one line actually does something, (Console.WriteLine("Welcome to PCP!");), the rest is “overhead”: for now, let’s take that to be a magical incantation, we’ll expound on that soon.
“Line by line” reading of the code:
- There are two statements in this code:
Console.WriteLine("Welcome to PCP!"); and using System;. They both end with ;.
- There are two kinds of comments (for the programmer and ignored by the computer): inline comment (
//…) and delimited, or multi-line, comments (/* … */),
Using directive. Namespace (= API, Library, i.e., set of classes)- The class has a header (l. 4), a body (l. 5-10), and a name (
Welcome).
- The method also has a header (l. 6), a body (l.7-9), and a name (
Main).
- The indentation (spacing) and the colors matter to the programmer, but not to the compiler.
Rules and Conventions
Rules
General rules for the syntax of C#:
- C# is case-sensitive.
- Every statement ends with a
;.
- Braces and parenthesis must be matched.
Oddly enough, C# does not care (almost at all) about spaces, but the programmer does: this is the difference between rules (use exact case, for instance) and conventions (like indentation, class name starting with an upper-case letter, …). Rules are required by the compilers, conventions are recommended by the programmers (and your instructors!).
There are also rules when we will be writing classes:
- You can have as many methods as you want per class.
- The
Main method is the entry point of a C# application.
Conventions
Some conventions include:
- Have only one class per file.
- The
.cs file has the same name as the class inside it.
Those are actually rules in Java!
Multiple Statements and Escape Sequences
Starting here, your instructor will draw at the board “Output window”, and will stop writing all the code, to focus on the Main method or notion at stake.
In our body, we can have multiple statements:
Console.WriteLine("Hey");
Console.WriteLine("Mom");
In addition to Console.WriteLine, we can also use Console.Write: the difference is that the former adds a new line after displaying the message, while the latter only displays the message, without adding a new line.
We can also use escape sequences for special characters:
\n - start a new line (newline character)\a - play a sound (alert)\t - horizontal tab
All of these use the escape character (\).
