VirtualBox is a program that simulates a computer. Operating system installed on VirtualBox runs inside a window, just like a normal program, and has no direct effect on host operating system.

Tiny Core Linux is one of the smallest Linux distributions (~9MB).

1. Download and install VirtualBox
2. Click on 'New', set name to 'tiny-core' and click next.
3. Choose enough ram (~800MB).
4. Select 'Create a virutal hard drive now' > 'VDI' > 'Dynamically allocated'

1. Download ISO image from HERE
2. Start the created virtual machine by double clicking on it.
3. When prompted with 'Select start-up disk', click the folder button and select the downloaded 'Core-current.iso' file.

This will start Tiny Core Linux from live CD, and will not install it on virtual drive, so all changes will be lost on restart; but you can choose 'Save the machine state' instead of 'Send the shudown signal' when closing virtual machine, and the state of machine will be preserved.
To exit from Virtual Machine window press right control.

$ tce-load -wi git
$ tce-load -wi compiletc

Check out this INSTRUCTIONS on how to install and configure Debian Linux on VirtualBox or on the hardware.