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General Introduction into Computer-Programming
for Newcomers
From the very beginning of the computers there have been 3 kinds of programming languages, the assembler-, interpreter- and compiler-languages. At those time many people did not know, that assemblers and compilers are software-programs, they thought this would be any hardware-machine.
The Assembler-Language is a very machine-close language with the bitwise and bytewise treatment of bits in the memory and the internal registers of the CPU (Central Processing Unit) by commands. The commands are written in Mnemonic-Code, which is easier to remember as hexadecimal-code and saves the programmer to write all commands in hex-code. Further the assembler offers the comfort, that symbolic names for memory locations can be used, called labels, instead of numeric memory addresses, whereby the assembler calculates the adresses of the labels automaticly after having got the start address of the program. For running the program the assembler converts the Mnemonic-code into machine-code, only this can be executed and programming-errors lead to a system crash. Every different kind of CPU must have a different assembler language. The machine-code can be reconverted into Mnemonic-Code by a disassembler, but all initial label-names are lost and replaced by substitute-names.
The interpreter language is used for higher languages in which mathematic formulas can be written similar as in mathematics etc. The program-code is called Source-Code and the program runs in Source-Code, whereby the interpreter converts linewise the Source-Code into Machine-Code before execution. The runtime of the interpreter language is longer as running compiled in machine code because the interpretation takes time.

In case of vbScript, which is an interpreter language, the interpreter needs not be added to the system, it is already included in the Windows Operation System. Programming-errors, made by the programmer, as there are syntax-errors and runtime-errors, are recognized by the system and error-messages are displayed. But errors can be dangerous for the system, therefor a vbScript-Editor should be used with a debugger (that is an error-finder). The program for first test is runned by the debugger, which generates error messages and if no error, program is executed. A vbScript-program can be run without a display, unless the code is extra written into the program.
The Source-Code of a program cannot be run, it must first be compiled, that means converted into machine-code, the so-called Object-Code. In the Object-Code all comments, variable- and procedure-names get lost. Normally the Object- Code is stored in Windows-Systems on hard-disk as a file with the extension *.exe , that means that the code can run in any location of the memory. Therefor the compiler makes at the beginning of the exe-file a header, which probably cares, that all absolute-addresses in the code are automaticly changed relative to the start address and no programmer ever since cares for that procedure.

In case of Visual Basic, which is a compiler language, the Visual Basic or Visual Studio, a huge program, is to download from a Microsoft website for free and to install, but since recently it must be registered, after a testing- time, by getting an ID by choosing a password. After opening the installed Visual Basic, all programming starts with the form, there is no program without a form. This is a rectangular area, displayed at runtime on the screen together with control-elements on it, for the program's input and output on the Windows screen, for the user-control of the program. The form is to be equipped by drag and drop with control-elements, from a tool-box as there are buttons, pull-down-menus etc. There is a long list of possibilities. Primary a start-button for starting the program. By a mouse-click on these elements the IDE (Integrated development environment) generates the code of a subroutine, which is, at runtime, started by the event handler, such an event can be the click on a button etc. Inside of these subroutines the own code or outside of them the own subroutine of the user can be written and called from inside. If during runtime no display is wanted, the user code or the subroutine-call can be placed into the subroutine of the form, thereafter the form switched invisible before closing the form (ending the program).
Erich Foltyn
Vienna, Austria
July 10th 2011