Computers & Operating Systems

Overview What's is a computer? Units of measurement Operating systems Unix

Computer Hardware Central Processing Unit (CPU) Main Memory (RAM) The heart and brains of a computer The device that performs all calculations and data manipulation in a computer Main Memory (RAM) The place the CPU looks for instructions and data to process

Computer Hardware Mass Storage (hard drive) Input/Output Devices Holds information not immediately needed by CPU Holds massive amounts of data Input/Output Devices keyboard, mouse, monitor, printer Devices used to move information into and out of the computer

Terminology - storage bit byte kilo- mega- Stands for Binary Digit. Smallest unit of storage in a computer A single 1 or 0 byte 8 bits Used to store single characters. (Sort of) ASCII characters kilo- Thousand kilobyte ~ 1,000 bytes Actually = 210 bytes (1,024) mega- Million Megabyte ~ 1,000,000 bytes. Actually = 220 bytes (1,048,576). About 350 pages of text

Terminology - storage giga- tera- Billion gigabyte ~ 1,000,000,000 bytes Actually = 230 bytes (1,073,741,824) About 360,000 pages of text tera- Trillion terabyte ~ 1,000,000,000,000 bytes Actually = 240 bytes (1,099,511,627,776) About 366 million pages of text

Terminology - processing power Clock speed The rate at which a CPU performs its basic operations CPU’s clock speed is measured in gigahertz (GHz) Gigahertz ~ billion hertz (billion pulses per second). 2.4 GHz CPU has a clock speed of 2,400,000,000 pulses per second. FLOPS Floating point operations per second MIPS Millions of instructions per second

What is an operating system? A computer program that Supports interaction between each user and the computer system Allocates computer resources, such as memory or CPU time, to other running programs Controls peripheral devices (disk drive, monitor, etc.) Common operating systems Windows XP, Macintosh OS, & Linux

One user or many? Most PCs are single-user machines 1 keyboard, 1 monitor, intended for one person They may run an OS capable of supporting multiple users, but not the hardware Large computer systems are designed for multiple users Still composed of the same 4 main components, but just made to work with many people at once A more sophisticated OS is required

Multitasking & Timesharing Unix is a multitasking operating system It can do more than one thing at a time Uses timesharing to accomplish this Works on one task at a time for very short amounts of time and rapidly switches between them Unix is also a multiuser operating system Allow many people to use the computer simultaneously

Components of Unix Kernel Shell File System Utilities The master control program of the computer. Shell The part of Unix that interprets user commands and passes them onto the kernel. File System Information stored on the computer. Can be organized into directories. Utilities Unix commands

History of Unix Designed to be portable — can be run on different computers Began in 1969 at AT&T’s Bell Labs (a.k.a. Lucent Technologies) Became a multi-user, multi-tasking Operating System The original Unix was freely distributed and many different companies took it, modified it, added features and released their own versions

Versions of Unix Over time, two main versions came to be the most popular. BSD (Berkeley Software Distribution) System V (AT&T Bell Labs) Most other versions of Unix are based on one of these two versions. Solaris (Sun Microsystems) SCO (Santa Cruz Operation) HP-UX (Hewlett-Packard Unix)

Linux Another version of Unix Created by Linus Torvalds While a graduate student in Finland Based on Minix by Andrew Tannenbaum Distributed freely Made to run on virtually all computer systems Red Hat is the most popular commercial distribution

Logging In Why do it? User name, login ID, login, ID, etc. Password Multi-user operating system Needs to know who you are User name, login ID, login, ID, etc. Each one is unique System administrators set up rules for user names Password Many systems have rules about acceptable passwords Keep it secret, keep it safe

Logging in — How to do it From PC labs Run a telnet program, such as PuTTY You'll find it in the programs menu Prompted for name and password

Unix interface Unix operates from a command prompt (alphaR) 1: Alphas use the EZ-Shell (created at UWM) Exit the EZ-Shell with option 62 Various GUIs do exist for Unix

Xwindows Created at MIT General protocol for running a GUI on Unix Handles the communication between the terminal and the server (main computer) You also need a “windows manager” to handle how the windows will look on your computer

Once you log on Messages Set terminal type Shell prompt Changing your password passwd Obtaining help man [command name]

Logging out How Type “exit” Type “logout” Why?