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A Brief Introduction to Smalltalk
written by Peter William Lount Version 2, Revised 20040907 Version 2, Revised 20040908, 8:44am PDT First version The simplicity, effectiveness and elegance of Smalltalk comes from it's simple yet highly expressive syntax and the design of it's various libraries of 'objects'. Smalltalk was the first, and remains one of the few, pure object systems, which simply means that everything in a Smalltalk program is an object. Smalltalk is generally recognized as the second Object Programming Language (OPL) (after Simula and "object" influences from Sketchpad, the B5000 and the 220 File System, see The Early History of Smalltalk, Section I), the first Pure Object Programming Langauge, the first true Integrated Development Environment (IDE), and the first IDE that eliminated the "Edit-Compile-Link-Run-Test-Debug" build cycle by integrating them all together so that cycle turn around time can be measured in seconds and all phases can be active at once - true interactive development! All of these features and capabilities have significant positive implications and important benefits. An object is a collection of data grouped together in meaningful ways with related operations, or chunks of programs, that manipulate that data. It is suprising how well this way of organizing software works. Objects get work done by sending 'messages' to each other. i.e. In english this would be like Jill saying to Jack, Jack drop the ball please. In Smalltalk this might be written as jack dropTheBall. Communication via messages is something that we're all familar with in our lives. Messages can be thought of as 'verbs' that ask the receiving object to perform an operation. Messages may have objects as parameters. i.e. In english this would be like someone saying to Jack, Jack pass the ball to Jill. In Smalltalk this might be written as jack passTheBallTo: jill or even more flexibly as jack pass: theBall to: jill so that other objects, like aPen, can be passed around. A nice example of accomplishing more with less. Smalltalk has a powerful concept known as "blocks" which are snippets of program code that are also treated as objects, this enables them to be used like any other object. In addition blocks enable you to extend the Smalltalk language very easily in powerful ways that other popular languages only dream of. Smalltalk was designed to be easy to learn and use. It is an expressive language that uses a simple sub set of human languages, nouns and verbs. Something that all humans can related to. This faciliates a clean expression of solutions that map very well with human thinking. This is one of the compelling reasons that Smalltalk programs tend to be one third to one half the size of programs written in other popular languages. Smalltalk programs typically can do two to three times as much work for the same amount of code. Often Smalltalk programs can actually do a lot more with much less code. Less code to write, re-write, test and maintain means a lower cost of development, a faster time to market, and potentially a higher quality of system which lowers maintenance costs again and opens new opportunities. The bottom line is that Smalltalk can work for you by letting you focus on your solutions and the rewards of your business endeavours. Copyright 1 9 9 9 - 2 0 1 0 b y S m a l l t a l k . o r g "! , A l l R i g h t s R e s e r v e d . |
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