What are the main differences between C++, C#, Java and Python?
C++, C#, Java, and Python differ in many ways. 
For example, the way programs written in each language are executed. C++ code is compiled so that the host machine can run it directly. C# and Java are compiled into byte code that can be executed by a virtual machine for Java JVM and for C# .NET. Python is an interpreter language where the Python interpreter executes each line at runtime. These differences have implications for both speed and compatibility.
Can you write a short program in each language so I can see the syntax differences?
Here are simple examples of the Hello World program, which is commonly used as a basic introduction to programming in various languages, in C++, C#, Java, and Python:

# C++

```cpp
#include <iostream>

int main() {
    std::cout << Hello World! << std::endl;
    return 0;
}
```

# C#

```csharp
using System;

class Program {
    static void Main() {
        Console.WriteLine(Hello World!);
    }
}
```

# Java

```java
public class HelloWorld {
    public static void main(String[] args) {
        System.out.println(Hello World!);
    }
}
```

# Python

```python
print(Hello World!)
```