Just Enough Unix, Chapter 1 Introduction to UNIX Just Enough Unix, Chapter 1

What is UNIX? Operating system (OS), software Widely used in industry, government, academia Excellent OS for multiuser systems

Operating System Functions Management of computer resources, such as memory, CPU, and I/O devices Enables interaction with the user Management of other software, scheduling

UNIX History Began as a joint venture called Multics involving GE, MIT, and AT&T’s Bell Labs Multics was too ambitious and by 1969 failed. Ken Thompson and Dennis Ritchie, who had worked on Multics, wrote Unics (later called UNIX) for a minicomputer at Bell Labs. In 1971 they wrote a UNIX-based word- processing system for the Bell Labs patent department. It was very successful.

UNIX History Bell Labs could not, by law, compete in the computer industry so they gave UNIX away for free. Computer Scientist at Universities introduced improvements. Berkeley produced its own version Many computer companies created their own versions. CS computers use Sun’s Solaris In 1991 Linus Torvalds created Linux, an OS similar to UNIX, for personal computers.

Open vs. Proprietary Proprietary: Designed to work only on certain types of computer hardware. MS-DOS (1980’s) ran only on machines with Intel CPU’s (Central Processing Unit) Original Macintosh OS ran only on machines with Motorola CPU’s Open: No single company developed or owns UNIX Unix is portable - runs on a variety of hardware

The Four Main Components of UNIX Kernel Manages resources (memory, i/o devices, etc.) File System Organization of data Shell Interprets user commands and passes them to the kernel Command-line interface Utilities Commands

The UNIX “Onion” File system File system File system File system Utilities Utilities Utilities Shell Shell Shell Kernel Kernel Kernel Hardware Hardware Hardware Hardware File system File system File system File system

Hardware Hardware is what determines what version, or type, of UNIX is installed. Miller uses Solaris 8 Machine Hardware is i86pc i386 Processor Grid uses Solaris 9 Machine Hardware is Sun4u Sun Sparc Processor

Kernel The kernel is the master control of the computer. Controls resources and schedules users jobs Programs interact with the kernel through system calls.

Shell Is the user - interface Interpreter between the user and the kernel. Takes commands from the user, decides if it is a valid command, then sends it to the kernel for processing. Consistency across shells allows many version of UNIX to appear to be the same.

Utilities / Applications The utilities are also known as the commands such as pwd, ls, cat Applications are software programs that allow users to solve specific problems. Development tools g++ , gcc complilers Debuggers and archivers Text Editors Pico, Emacs, Vi Email tools Pine, Elm, Mail

File System How all the data is organized on the system. The hierarchal file structure allows for organization of files into related groups The similar structure across many different UNIX systems makes each system feel familiar to the user.