You cannot create folders with these names

In Windows OS, no one can create a folder with these names. Because all the names are Windows Inbuilt "Reserved Device Names". 

1. CON, 
2. PRN, 
3. AUX, 
4. CLOCK$, 
5. NUL, 
6. COM1, 
7. COM2, 
8. COM3, 
9. COM4, 
10. COM5,
11. COM6, 
12. COM7, 
13. COM8, 
14. COM9, 
15. LPT1, 
16. LPT2, 
17. LPT3, 
18. LPT4, 
19. LPT5, 
20. LPT6,
21. LPT7, 
22. LPT8, 
23. LPT9

But this is also possible now. You can create folders with these name by simple trick.

Step1: Create a new folder

Step2: Type the anyone of the name from above list.

Step3: Don't press Enter once you type the name.

Step4: After type the name Press and Hold " Alt + 255" 

Step5: Then leave it.

Step6: Finally you create.