Evaluation of smalltalk

EVALUATION OF SMALLTALK

Small talk  what The First Programming Language That fully supported object_oriented programming.

DESIGN PROCESS

The concepts of Smalltalk Which originated in the Ph.D work of Alan Kay.

Kay envisioned machines Which were seem to execute a million or more instructions per second and megabytes of memory.

He Believed That desktop computers would be used by non programmers and need very powerful human-interfacing capabilities.

The user Should interact with the display through keystrokes and by Touching the screen with his finger.

Smalltalk-80 and the Xerox hardware nearly matched the early version of Alankay.

LANGUAGE OVERVIEW

In Smalltalk, the objects range from integer constants to larg Complex Software Systems.

All computing is done by the same uniform technique sending a message to to object to invoke one of its methods.

A message is sent to a data object, Specially to one of the methods defined for the object.

A subprogram is a message to the code of the subprogram.

Object classes are abstractions and the instanc of the class can be created.

The syntax of the Smalltalk is different from otherlanguage Because of the use of messages more than arithmetic and logic expression and Conventional control statements.

EVALUATION

It permits two separate aspects of computing.

* Graphical User Interface

* Object Oriented Programming.

EXAMPLE

"Smalltalk Example Program"

 ClassName polygon

Super Class Object

Instance variable name ourpen

Num Sides

SideLength

New

       ^ Super New getpen

Getpen

          Ourpen <- new default pen Nib: 2

Draw

          NumSides times repeat

Length = Len

SideLength <-LEN

Side: num

 Numside <-num