Reverse H4ck3r: OS

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Friday, September 2, 2011

Advance Operating System

New Advance Operating System Designed For Security..

Qubes is an open source operating system designed to provide strong security for desktop computing. Qubes is based on Xen, X Window System, and Linux, and can run most Linux applications and utilize most of the Linux drivers.

In the future it might also run Windows apps.

How Boot Loaders Work

What BIOS does for Us :

The BIOS is the firmware in the ROM of a PC. When the PC is powered up, the BIOS is the first program that runs. All other programs must be loaded into RAM first. The BIOS contains the following parts:

POST (Power On Self Test). The running counter that counts the kilobytes of main memory is the most visible part of the POST.
The Setup Menu, that lets you set some parameters and lets you adjust the real time clock. Most modern BIOS versions let you set the boot order, the devices that BIOS checks for booting. These can be A (the first floppy disk), C (the first hard disk), CD-ROM and possibly other disks as well. The first device in the list will be tried first. Older BIOS-es have only one boot order: A, C. So the BIOS will try to boot from A first and if there is no diskette in the drive it tries to boot from C.
The boot sector loader. This loads the first 512-byte sector from the boot disk into RAM and jumps to it. This is where the boot loaders described in this paper start.
The BIOS interrupts. These are simple device drivers that programs can use to access the screen, the keyboard and disks. Boot loaders rely on them, most operating systems do not (the Linux kernel does not use BIOS interrupts once it has been started). MSDOS does use BIOS interrupts.