What is HAL

A hardware abstraction layer (HAL) is an abstraction layer, implemented in software, between the physical hardware of a computer and the software that runs on that computer. Its function is to hide differences in hardware from most of the operating system kernel, so that most of the kernel-mode code does not need to be changed to run on systems with different hardware. On a PC, HAL can basically be considered to be the driver for the motherboard and allows instructions from higher level computer languages to communicate with lower level components, such as directly with hardware.

The Windows NT operating system has a HAL in the kernel space, between hardware and microkernel, drivers, executive services.[1][2] This allows portability of the Windows NT kernel-mode code to a variety of processors, with different memory management unit architectures, and a variety of systems with different I/O bus architectures; most of that code runs without change on those systems, when compiled for the instruction set for those systems. For example, the SGI Intel x86-based workstations were not IBM PC compatible workstations, but due to the HAL, Windows NT was able to run on them.

What is an inode

From linfo.org

An inode is a data structure on a filesystem on Linux and other Unix-like operating systems that stores all the information about a file except its name and its actual data.

A data structure is a way of storing data so that it can be used efficiently. Different types of data structures are suited to different types of applications, and some are highly specialized for specific types of tasks.

A filesystem is the hierarchy of directories (also referred to as the directory tree) that is used to organize files on a computer. On Unix-like operating systems, the directories start with the root directory (designated by a forward slash), which contains a series of subdirectories, each of which, in turn, may contain further subdirectories, etc. A variant of this definition is the part of the entire hierarchy of directories or of the directory tree that is located on a single hard disk drive (HDD) or other storage device or on a single partition (i.e., a logically independent section of a HDD).

A file is a named collection of related information that appears to the user as a single, contiguous block of data and that is retained in storage. It does not automatically contain information about itself (e.g., its size, when it was created or where it is located on the system), unless some human purposely adds in such data. Such information about a file, in contrast to the data contained in a file, is its metadata (i.e., data about data).

Storage refers to computer devices or media that can hold data for relatively long periods of time (e.g., years or decades), such as disk drives and magnetic tape. A directory (referred to as a folder on some operating systems) in Unix-like operating systems is merely a special type of file that associates file names with a collection of inodes.

When a file is created, it is assigned both a name and an inode number, which is an integer that is unique within the filesystem. Both the file names and their corresponding inode numbers are stored as entries in the directory that appears to the user to contain the files. That is, the directory associates file names with inodes.