1
Software
The intelligence of the computer Computer programs, or instructions to
perform a specific task Determines what hardware is present Decides how hardware is configured
and utilized Uses hardware to perform tasks
1
Three Types of Software and What They Do
Firmware (BIOS)• Controls computer’s input/output functions
Operating systems (OSs)• Provide instructions to hardware to perform
tasks Applications software
1
Firmware or BIOS
Provides basic instructions to hardware Often serves as the interface between
higher-level software and hardware
1
Software Layers
A hierarchy determines how software interfaces so that high-level software can depend on low-level software to manage the hardware for it
Applications software depends on the OS to interface with hardware• Instructs hardware directly• Uses BIOS to provide the instructions• Uses device drivers
1
Operating Systems
Different operating systems are written to support different types of hardware systems and user needs
1
Functions of Operating Systems
Manage BIOS Manage files on secondary storage devices Manage primary memory (RAM) Diagnose software and hardware problems Interface between hardware and software Perform housekeeping procedures requested
by user
1
Starting Up the Operating System
OS programs must be copied from secondary storage into RAM (memory)
CPU then reads from one memory location in RAM to another to receive and follow instructions
1
Interfacing with the Operating System
Command-driven interface Menu-driven interface Icon-driven interface (graphical user
interface or GUI)
1
Survey of Operating Systems
Terms• Multitasking• Cooperative multitasking (task switching)• Preemptive multitasking• Environment• Windows 3.x operating environment
1
Comparison of Operating Systems
What kind of user interface is provided? Can the OS support multitasking? Can the OS easily manage large quantities of
primary memory (RAM) and secondary storage?
How many and what kinds of applications are written to work with the OS?
How powerful must the hardware be to make efficient use of the OS?
How does the OS perform in a network?
1
Well-known Operating Systems
DOS (disk operating system) DOS with Windows 3.1 and 3.11 operating
environments Windows 95 and Windows 98 UNIX operating system Windows NT Windows 2000 OS/2 Macintosh operating system