SOLID principles to apply while writing programming code are:

 SOLID principles to apply while writing programming code are:

1. Single Responsibility Principle: Each unit should be responsible for only one thing.
2. Open-Closed Principle: Systems should be open for extension but closed for modification.
3. Liskov Substitution Principle: Substitutions of subclasses should preserve properties of superclass.
4. Interface Segregation Principle: Interfaces should be segregated based on their responsibilities.
5. Dependency Injection Principle: Dependency on abstractions rather than concretions.