Explain the principles underlying the SOLID concept and their impact on software system development.

SOLID principles are a set of five fundamental object-oriented design principles that help create flexible, extendable, and maintainable systems:

1. Single Responsibility Principle (SRP) — The principle that a class should have only one reason to change, meaning it should be responsible for a single specific task.

2. Open/Closed Principle (OCP) — The principle that classes should be open for extension but closed for modification.

3. Liskov Substitution Principle (LSP) — The principle that objects of a subclass should be interchangeable with objects of the base class without affecting the correctness of the program.

4. Interface Segregation Principle (ISP) — The principle that clients should not depend on interfaces they do not use. It's better to have several specific interfaces than a single universal one.

5. Dependency Inversion Principle (DIP) — The principle that high-level modules should not depend on low-level modules; both should depend on abstractions.

Impact on development:

• Improves code readability and maintainability.
• Facilitates testing and refactoring.
• Allows easy extension of functionality without changing existing code.

Example of SRP:

// Bad: class responsible for both logic and output
class Report {
    public string Data { get; set; }
    public void Print() { /* output to screen */ }
}

// Good: separation of responsibilities
class Report {
    public string Data { get; set; }
}
class ReportPrinter {
    public void Print(Report report) { /* output to screen */ }
}