A Little Smalltalk

Chapter 1 The traditional model describing the behavior of computers in basic execution programs is the process state or "hole of the dove" model. In this view, the computer follows a number of instruction patterns, roams in memory, extracts values ​​from various slots (memory addresses), converts them in some way, and pushes back the results to other slots It is a data manager. . By examining the value of the slot you can determine the state of the machine or the calculation result.

In the last article about Smalltalk, I did not mention what was done using a virtual machine or VM. The idea behind the virtual machine is to compile the general purpose opcode of a general-purpose CPU that exists only as a paper design, not using the compiler to convert the source code to the specific processor's opcode. SmallTalk is the first programming language, especially dependent on the VM. The VM is an emulator that simulates this imaginary CPU by converting its general purpose opcode to the actual opcode of the physical CPU on which it is running. You can create the required number of virtual machines, virtual machines running on IBM CPU, virtual machines running on Sun SPARC, virtual machines running on Intel chips, and virtual machines running on ARM chips of mobile phones . After converting the program to the VM's general opcode, the program runs on all these platforms.

Many of the first true object-oriented languages ​​considered by the Smalltalk language were developed by Xerox at the research center in Palo Alto, California in the early 1970s. In Smalltalk, it is almost impossible to write programs that are all objects and not object-oriented. Smalltalk is not just a programming language, it is a programming interactive environment that allows you to modify parameters and code during program execution. Smalltalk supports the concept of inheritance and sending messages between objects

Smalltalk was originally written in 1972 for the first time, but it was kept in Xerox Palo Alto Research Center (PARC) for 8 years. In 1980, a new version was released and distributed to four companies for peer review and implementation. HP, Digital Equipment, Tektronix, and Apple. In terms of the importance of Smalltalk and its impact on computer and programming productivity, Smalltalk evaluates to be equal to C, but one of the many ways to influence is the development environment. The integrated development environment (IDE) became common, but before Smalltalk, most programmers used the text editor to create the code (in recent years some of them are coming back). In addition to organizing the code in the repository, Smalltalk comes with a special tool that allows you to check which code is associated with other bits and to check the code at run time.