History of Unix Development

History and Evolution of Unix and Linux

• Greg Chesson, a graduate student at UIUC, played a key role in licensing negotiations for UNIX at Bell Labs.
• Unix surged in popularity during the late 1970s and early 1980s, adopted by startups like DYNIX, HP-UX, SunOS/Solaris, AIX, and Xenix.
• AT&T's Unix System Laboratories and Sun Microsystems collaborated in the late 1980s to develop System V Release 4 (SVR4), widely embraced by commercial vendors.
• By the 1990s, over 90% of the fastest supercomputers globally ran Unix or Unix-like systems, aided by collaborative development of BSD and Linux.
• In 2000, Apple launched Darwin, a Unix-based OS that became the foundation of macOS.
• As of 2020, Unix operating systems are prevalent in modern servers, workstations, and mobile devices.

Microsoft vs. Unix

• Microsoft dominated the desktop market with Windows GUIs: Windows 3.1, 95, 98, NT, and 2000.
• To compete, UNIX adopted X Windows, developed at MIT, to provide a graphical interface.

GNU and Linux

• Richard Stallman founded the Free Software Foundation and initiated the GNU project, offering free software tools for Unix-like systems.
• Linus Torvalds, in 1991, launched the Linux kernel as a personal project, inspired by the MINIX OS.
• Linux evolved into a leading OS used across diverse applications, including smartphones and supercomputers, due to its open-source nature.

Unix's File and Process Management

• Files in Unix are arrays of bytes capable of holding various data types, organized in a hierarchical structure.
• A process represents a running instance of a file, highlighting the distinction between static data and dynamic execution.

System Calls and POSIX Standards

• System calls act as the interface between user applications and the kernel, enabling file operations such as open, write, read, and close.
• POSIX (Portable Operating System Interface) standardizes system calls for compatibility among Unix-like systems.

Unix Environments

• Unix operates in varied environments:
  • Stand-alone personal environment: single-user systems like laptops and desktops.
  • Time-sharing systems: multiple users sharing a single machine’s resources.
  • Client/server systems: clients requesting resources from centralized servers.

Core Components of Unix

• The kernel manages system resources, multitasking, and device control.
• The shell interprets commands and enables scripting for program automation.
• Utilities perform specific functions such as editing and processing data.

Internal and External Commands

• Internal commands are built into the shell, enabling direct execution without external files (e.g., cd, echo).
• External commands exist as separate executable files, requiring the shell to locate and execute them (e.g., ls, cat).

Command Type and Exit Status

• The type command identifies whether a command is built-in, a shell function, an alias, or an executable file.
• Exit status can be checked using echo $? after running a command.

Manual Pages and Searching Commands

• The man command provides documentation for commands, using a pager for navigation.
• The man -k command searches through manual page descriptions by keyword, assisting in finding related commands.
• The apropos command lists commands associated with a specified keyword, while whatis provides brief descriptions of commands.

Special Characters in Unix

• . denotes the current directory, .. signifies the parent directory, / represents the root directory, and ~ indicates the user's home directory.

User Information Commands

• The who command displays user login details, including username, terminal type, and login timestamp.
• The command w efficiently presents similar information with less typing.

Explore the pivotal moments in the history of Unix, from its development at Bell Labs to its widespread adoption in commercial startups during the late 1970s and 1980s. Learn about the significant contributions of key figures and the evolution of various Unix systems like BSDO and System V.