A "killer app" is not always an especially good application. What a killer app needs to be is the right product, at the right time, in the right competitive environment to turn potential into reality for enough users to create a critical mass. With the question "What's the killer app for Vista?" on the minds of many, here's a look at what's made apps "killers" during the first few decades of personal computing.

1976

Electric Pencil

People who never wanted a computer still wanted the perfect typewriter, and Electric Pencil for CP/M machines (cloned as EasyWriter for IBM PCs) made that a reality.

1978

WordStar

Once a user had been conditioned by its unintuitive but memorable interface, anything that didn't run WordStar was not a usable PC.

1979

VisiCalc

Often called the first killer app, this pioneering spreadsheet tool gave birth to the demand, "I need this software and something that runs it."

1981

dBASE II

Minicomputers costing far more were replaced by PCs when dBASE II put just enough almost-relational rigor—and an accessible programming language—on desktops.

1982

AutoCAD

Proprietary drafting systems got a chill wind down their necks when Autodesk told people they could put a numeric coprocessor in that empty socket on a PC mother-board.

1982

WordPerfect

The DOS-based WordPerfect was, ironically, a killer app for DOS—after the debut of Windows

and several graphical word processing products for the Macintosh, Windows and OS/2.

1983

Turbo Pascal

No other programming tool before or since has ever made such a huge triple jump in programmer convenience, performance and affordability.

1983

Lotus 1-2-3

Written in down-to-the-metal machine code for performance that left competitors gasping, Lotus 1-2-3 put graphics into the spreadsheet and gave rise to many user interface clones.

1984

MacWrite/MacPaint

Without this multifont, graphically enabled word processor and its companion illustration tool, the original Mac would have been nothing; with them, it needed almost nothing else.

1984

MultiMate

For companies wedded to their Wang word processors, the appearance of a work-alike for PCs finally made those less costly and more flexible machines an option.

1985

Excel for Macintosh

Making 1-2-3 suddenly seem comparatively crude, Microsoft's Excel set a new standard for direct manipulation of the venerable spreadsheet interface as well as a new standard for elegant graphics.

1985

Aldus PageMaker

Essentially creating the notion of mass-

market desktop publishing, PageMaker gave the Mac a beachhead in the creative arts that it still retains.

1986

Cross-network

e-mail (MCI and

CompuServe)

No single communication software product opened digital communication to Everyman, but cross-network e-mail presaged the day when everyone would have an @ address.

1987

Excel for Windows

Having given the Mac a jumpstart that no one else could have provided, Microsoft migrated its hard-earned GUI skills to the open hardware of the PC—and things changed.

1988

Mathematica 1.0

One of the most distinctive applications for the short-lived NeXT Computer, Mathematica still sets the standard for symbolic math and visualization on Windows, Mac, Linux and Unix systems.

1989

Word for Windows

Combining much of the power of desktop publishing with an interface comparable to anything on the Macintosh, Microsoft's Word for Windows began the mainstreaming of the GUI.

1990

Photoshop

With a name that's become a verb meaning "to manipulate or fabricate an image," Adobe Systems' Photoshop is more than a program—it's the visual artistic medium of our age.

1990

Windows 3.0

More an environment than an operating system, Microsoft's Windows 3.0 was far from being as capable as the Mac—but looked good enough to prevent major Mac gains while Windows matured.

1991

Visual Basic

Originally conceived as a dual-platform tool, Microsoft's VB abandoned planned OS/2 capability just before the 1.0 release, opening a leadership gap for Windows development that IBM would never close.

1994

Navigator 1.0

Arguably killed too soon by Microsoft's Internet Explorer to be called a killer app itself, Netscape Navigator still deserves a place on this list as the application that redefined "surf."

1995

Internet Explorer 1.0

Originally an add-on, IE quickly became the linchpin of Microsoft's strategy to integrate Internet connectivity and protocols such as HTML into the desktop environment.

1996

Palm's HotSync

A breakthrough for convenient "companion computing," the HotSync functionality of the Palm platform drove a huge expansion in the use of handheld devices.

2001

OS X

Apple's Mac OS X (Roman numeral 10, not letter "X") was a breakthrough on almost too many levels to count. It restored Apple's competitiveness in true multitasking after years of neglect that ceded the desktop operating system lead to Microsoft; it put a mainstream GUI on a robust Unix foundation; and, behind the scenes, it paved the way

for the second complete replacement of the Macintosh processor architecture.

2001

iTunes

A brilliant fusion of UI upfront and e-commerce interaction behind the scenes, iTunes and the iPod put a halo on the Apple brand.

2004

Firefox 1.0

Bringing open-source development out of its geek-centric niche into the mainstream, the Mozilla Foundation's Firefox served notice that secure and simple applications were in demand.