Computer and Information Science Computer Software Computer Software Chapter 1.2

AgendaAgenda n Application Software n Operating Systems

SoftwareSoftware n Software is the programs and data that a computer uses. n Programs are lists of instructions for the processor. n Data can be any information that a program needs: character data, numerical data, image data, audio data, and countless other types. –Digitizing : –Digitizing :The process of taking a visual image, or audio recording and converting it to a binary form for the computer.

Types of Programs n Imagine that you have just turned on your computer and have not yet started any application. Are any programs running? n Two types of software –Application software –System software/Operating systems

Why do we need an OS? n n What are the goals of an Operating System? –The primary goal of an Operating System is to make the computer system convenient to use. –The secondary goal is to make the computer system efficient to use.

An Operating System n n It underlies all other software. n acts as an interface between a user of a computer and the computer hardware n It acts as an interface between a user of a computer and the computer hardware n It manages and coordinates computer system resources ( CPU, memory, file system, I/O devices) n n It provides the user Interface that is: –How can something as simple-minded as a processor and memory present you with something as rich as the Mac or Windows GUI?

Operating system services... Control basic input and output Allocate system resources Manage storage space

Operating Systems Detect equipment failure Maintain security Operating system services...

You ask MS Word to OPEN a document –File menu/Open… –WHAT WILL YOU SEE? –What really just happened in the box? WORD called on O.S. to present you with that file list! O.S. must look at: 1.Disk Directory (list of filenames) 2.File Allocation Table (FAT)…. (list of file locations: starting position/cluster number on the disk) System calls

Multi-tasking n n >1 program or person can share computer resources. –CPU is idle ~90% of time, waiting for user input ! –One program active; Others running in the background OS must protect each program ’ s memory area to ensure that instructions and data don ’ t “ leak ” into an area allocated to another program. If it fails, programs can crash … more shortly!

Booting and BIOS n When a computer is started up, the hardware will automatically load the operating system and start it running. This process is called booting. n BIOS is the boot program on a computer, and controls the computer from the time you start it up until the operating system takes over. When you turn on a PC, the BIOS first conducts a basic hardware check, called a Power-On Self Test (POST), to determine whether all of input/output devices are present and working. Then it loads the operating system into your computer's RAM.

ROM (Read-only-Memory) n ROM refers to computer memory chips containing permanent or semi-permanent data. Unlike RAM, ROM is non-volatile; even after you turn off your computer, the contents of ROM will remain. n BIOS is stored in a ROM.

Various Operating Systems n n Windows : Developed by Microsoft XP, Vista, windows7 n n Unix: Developed by AT&T for large companies n n Linux: Open Source version of Unix n n Mac OS: only for Mac hardware e.g. Snow Leopard

UNIX SunOS UNIX login: smith Password: Last login: Oct 15 17:42:09 from tserv1.edu SunOS Release #1: Wed Mar 20 11:24:14 AST 1991 You have mail. % _ UNIX features a command line interface. Designed for minicomputers but is now also available for micros and mainframes. The UNIX prompt Microcomputer Operating Systems Why is it important for me to know which operating system is on my computer?

IMPORTANT ! WHAT HAPPENS when you SHUT DOWN improperly? Why should you care? “Shutting down incorrectly is a little like stopping your car by driving it into a wall. It works, but it can cause some damage.”

Computer terms bingo n Follow the link _Resources/KnowYourComputerTe rms.swf _Resources/KnowYourComputerTe rms.swf