Binary files are usually thought of as being a sequence of bytes, which means the binary digits (bits) are grouped in eights. Binary files typically contain bytes that are intended to be interpreted as something other than text characters. Compiled computer programs are typical examples; indeed, compiled applications are sometimes referred to, particularly by programmers, as binaries. But binary files can also mean that they contain images, sounds, compressed versions of other files, etc. — in short, any type of file content whatsoever.
Some binary files contain headers, blocks of metadata used by a computer program to interpret the data in the file. The header often contains a signature or magic number which can identify the format. For example, a GIF file can contain multiple images, and headers are used to identify and describe each block of image data. The leading bytes of the header would contain text like GIF87a or GIF89a that can identify the binary as a GIF file. If a binary file does not contain any headers, it may be called a flat binary file.
In Unix and operating systems inspired by it, the file system is considered a central component of the operating system.
It was also one of the first parts of the system to be designed and implemented by Ken Thompson in the first experimental version of Unix, dated 1969.
Like in other operating systems, the filesystem provides information storage and retrieval, as well as interprocess communication, in the sense that the many small programs that traditionally comprise a Unix system can store information in files so that other programs can read these, although pipes complemented it in this role starting with the Third Edition. Additionally, the filesystem provides access to other resources through so-called device files that are entry points to terminals, printers, and mice.
The rest of this article uses "Unix" as a generic name to refer to both the original Unix operating system as well as its many workalikes.
The filesystem appears as a single rooted tree of directories. Instead of addressing separate volumes such as disk partitions, removable media, and network shares as separate trees (as done in MS-DOS and Windows: each "drive" has a drive letter that denotes the root of its file system tree), such volumes can be "mounted" on a directory, causing the volume's file system tree to appear as that directory in the larger tree. The root of the entire tree is denoted /.
Salman the Persian or Salman al-Farsi (Arabic:سلمان الفارسي), born Ruzbeh (Persian:روزبه), was a companion of the Islamic prophetMuhammad and the first Persian who converted to Islam. During some of his later meetings with the other Sahabah, he was referred to as Abu Abdullah ("Father of Abdullah"). He is credited with the suggestion of digging a trench around Medina when it was attacked by Mecca in the Battle of the Trench. He was raised as a Zoroastrian, then attracted to Christianity, and then converted to Islam after meeting Muhammad in the city of Yathrib, which later became Medina. According to some traditions, he was appointed as the governor of Al-Mada'in in Iraq. According to popular Shia tradition, Muhammad considered Salman as part of his household (Ahl al-Bayt). He was a renowned follower of Ali ibn Abi Talib after the death of Muhammad.
Birth and early life
Salman was a Persian born either in the city of Kazerun in Fars Province, or Isfahan in Isfahan Province, Persia. In a hadith, Salman also traced his ancestry to Ramhormoz. The first sixteen years of his life were devoted to studying to become a Zoroastrianmagus or priest after which he became the guardian of a fire temple, which was a well-respected job. Three years later in 587 he met a Nestorian Christian group and was so impressed by them. Against the wishes of his father, he left his family to join them. His family imprisoned him afterwards to prevent him but he escaped.