1 DOS with Windows 3.1 and 3.11 Operating Environments n Designed to allow applications to have a graphical interface DOS runs in the background as the true OS and uses Windows 3.x as the middle layer between the application and DOS n Has been replaced with Windows 9x

1 DOS with Windows 3.x

1 Windows 95 and 98 n Do not completely eliminate DOS n Windows 95 Windows for Workgroups (Windows 3.11) plus DOS 7.0 Introduced Plug and Play capability n Windows 98 Supports larger hard drives and more hardware devices Includes more software utilities Faster than Windows 95 The last Microsoft OS with a DOS foundation

Windows 9x

1 UNIX n Originally written for mainframe computers in the early 1970s n Now a popular OS for networking n Linux A variation of UNIX that is free to everyone

1 UNIX

1 Windows NT n Completely eliminates the underlying relationship with DOS n Supports preemptive multitasking and multiprocessing n Designed to work within a powerful networked environment (client/server)

1 Windows NT

1 Windows 2000 n A suite of operating systems, each designed for a different sized computer system Windows 2000 Professional Windows 2000 Server Windows 2000 Advanced Server Windows 2000 Datacenter Server n Built on Windows NT architecture n Designed to ultimately replace both Windows 9x for low-end systems and Windows NT for midrange and high-end systems

1 Windows 2000

1 OS/2 n Written by IBM in cooperation with Microsoft Corporation n Provides an altogether different OS in place of DOS n Slow to gain popularity due to: Errors in earlier versions Large computer hardware requirements

1 OS/2

1 Macintosh Operating System n Available only on Macintosh computers n Offers easy access to the Internet n Allows any Macintosh computer to become a Web server for a small network

1 Macintosh Operating System

1 How an Operating System Manages an Application n DOS naming conventions Filename (up to 8 characters) File extension (3 characters) n Memory addressing under DOS

1 Operating System Modes n Real mode Single-tasking operating mode whereby programs:  Only have 1024K of memory addresses  Have direct access to RAM  Use a 16-bit data path n Protected mode Supports multitasking whereby:  The OS manages memory  Programs have more than 1024K of memory addresses  Programs can use a 32-bit data path

1 Real Mode

1 Protected Mode

1 Applications Software n Designed to work on top of a particular OS n Comes written on floppy disks or CD- ROMs; usually must be installed on a hard drive in order to run

1 Categories of Applications Software n Word processing n Spreadsheet n Database management n Graphics n Communications n Games n Mathematical modeling n Software development tools

1 How Applications Software is Loaded and Initialized 1.OS receives command to execute application 2.OS locates program file for the application 3.OS loads program file into memory 4.OS gives control to the program 5.Program requests memory addresses from OS for its data 6.Program initializes itself; it may request that data from secondary storage be loaded into memory 7.Program turns to user for its first instruction

1 How Applications Software is Loaded and Initialized

1

1 Launching a Program File

1 Rules DOS Uses to Search for Executable Program Files 1.If no path is given before the filename, DOS looks in the current directory 2.If no path is given and the file is not in current directory, DOS looks in paths given to it by the last PATH command executed 3.If there is a path given in front of filename in the command line, DOS looks in that path 4.If there is a path given but the file is not found in that path, DOS looks in paths given to it by the last PATH command executed

1 Copying the Program into Memory

1 Loading Application Software Using Windows 9x n Place shortcut icon directly on desktop n Click Start button; select Programs; select program from list of installed software n Use Run command, after clicking Start button on the taskbar

1 Loading Application Software Using Windows 9x

1

1 Applications Software Summary n Applications software is executed by either the operating environment (Windows 3.x) or the OS software (DOS or Windows 9x) n When an application is executing, you are interacting with the application n Applications software interacts with OS software that is executing it n OS software interacts with hardware n OS software might interact with the hardware through BIOS or the device driver

1 Chapter Summary n Individual components that make up a computer system: hardware and software n Hardware Devices used for input, output, processing, and storage of data Components that make up the electrical system Components used for communicating data and instructions from one device to another  Importance of buses on the system board continued

1 Chapter Summary n CPU Central processing point for all data and instructions Both data and instructions must be stored in memory with assigned memory addresses before processing can begin continued

1 Chapter Summary n Software Works in layers  Lowest layer (BIOS and device drivers) interfaces with hardware  Highest layer (applications software) interfaces with user OS is the middleman layer that coordinates everything