Smalltalk is a small language, although the Smalltalk system is large. The syntax of the language is simple and very regular. It is a good example of the power that can be provided by a small language if that language is built arould a simple but powerful concept. In the case of Smalltalk, that concept is that all programming can be done using only a class hierarchy built using inheritance, objects, and message passing.
In comparison with conventional compiled imperative language programs, equivalent Smalltalk programs are significantly slower. Although it is theoretically interesting that array indexing and loops can be provided within the message-passing model, efficiency is an important factor in the evaluation of programming languages. Therefore, efficiency will clearly be an issue in most discussions of the practical applicability of Smalltalk.
Smalltalk's dynamic binding allows type errors to go undetected until run time. A program can be written and compiled that includes messages to nonexistent methods. This causes a great deal more error repair later in the development than would occur in a static-typed language.
The Smalltalk user interface has had an important impact on computing: The integrated use of windows, mouse-pointing devices, and pop-up or pull-down menus dominate contemporary software systems.Perhaps the greatest impact of Smalltalk is the advancement of object-oriented programming, now the most widely used design and coding methodology.