When iam pressing the f4 it will show s boot manager is missing in samsung n150. how to create a recovery drive

If this is fixable, it will be fixed by the following. If these fail to run or don't work, then chances are the drive has died :(

If this is Windows 8/10 just retry a few times until it does an "Automatic Repair" after it gives a blue screen saying it couldn't fix it, click on advanced, then find the Command Prompt.

For Windows Vista/7 you will need a Windows USB or CD. Boot to that and instead of installing Windows choose Repair my Computer. Then select the command prompt from the list.

Now that you have a command prompt type the following, and press enter after each line:
bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd
bootrec /scanos
bootsect.exe /nt60 all /force

That fixes the issue, or you'll need a new drive my friend.
Link to source article:

How to use the Command Prompt to fix issues with your PC boot records...

You should be able to press 'F4' at boot time and access Samsung Recovery Software, and then reinstall the back-up that would have been made the first time the netbook was switched on - a 'factory reset'...

if you boot pressing F8 can you get to the repair option?

You should be able to press 'F4' at boot time and access Samsung Recovery Software, and then reinstall the back-up that would have been made the first time the netbook was switched on - a 'factory reset'...

You should be able to press 'F4' at boot time and access Samsung Recovery Software, and then reinstall the back-up that would have been made the first time the netbook was switched on - a 'factory reset'...

Try pressing f4 during boot at bios this should take you to the recovery partition with options to back up to removable media then restore to factory image.

In first remove battery, then one press turn on buttom, then put battery, and turn on.
if will not resaults,

reinstall operating system from CD/DVD

after the coputer restarts press f4 and it should go itno recovery mode and ask you to restore the computer

1.Insert the Windows XP CD-ROM into the CD drive, and then restart the computer.
2.Click to select any options that are required to start the computer from the CD drive if you are prompted.
3.When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
4.Press 1 (One) to select windows XP and then hit enter.
5.When you are prompted, type the Administrator password. If the administrator password is blank, just press ENTER.
6.At the command prompt, Type Bootrec /RebuildBcd and then press ENTER.
7.If the Bootrec.exe tool runs successfully, it presents you with an installation path of a Windows directory. To add the entry to the BCD store, type yes. A confirmation message appears that indicates the entry was added successfully. 8.If the Bootrec.exe tool cannot locate any missing Windows installations, you must remove the BCD store, and then you must re-create it. To do this, type the following commands in the order in which they are presented. Press ENTER after each command.
Bcdedit /export C:\BCD_Backup

ren c:\boot\bcd bcd.old

Bootrec /rebuildbcd

1.Restart the computer

unfortunatlly your os has crashed you can try to recover your info by taking ur hard drive out which can be ticky and costly.
I suggest reinstaling your os