Interpretors Compilers and Virtual Machines

Although compilers exist for QBasic, while running in the QBasic environment your code is being interpreted. In the same way that a Microsoft office document program needs an office program loaded to view or edit so a QBasic program needs Qbasic loaded onto the computer to execute. Compiled programs on the other hand need no host program and can run independently on any computer designed to run the code. An interpreter, as the name suggests interprets a program into a form that the CPU (Central Processing Unit) understands. Of course this interpretation takes time so interpreted programs generally take far longer to execute so they are not very good for fast action games or smooth graphics. Compilers on the other hand compile source code programs directly into a form understood by the CPU and therefore generally run much faster which is why all modern games programs are compiled. However the disadvantage of compiled programs is that they are CPU specific so if a program is compiled to run on an x86 instruction code set (x86 being CPU series type) it cannot be executed directly on an apple computer (until recently at least) without access to the source code and recompilation on the host machine.  On the other hand if the host machine is loaded with QBasic a program should run directly without alteration (not strictly true).

Batch file programs and batch file programming is a form of script that is designed to be executed by a command interpretor. Contained with versions of DOS (Disc Opperating System) is a program  called COMAND.COM (.COM stands for an executable program less then 65k in size while .EXE stands for an executable more than 65k) which is the first program to load after the operating system  boot up and is a shell program that carries out simple user commands such as DIR which displays a list of files contained in a particular directory. In the DOS system the first batch program that would automatically run when a computer was booted up was the AUTOEXEC.BAT file which would automatically run programs that were needed to control additional hardware such as graphics and sound cards. Also in the early days of Windows up to Windows 98, windows would only automatically run because of the line 'WIN' at the end of the AUTOEXEC.BAT. The Windows systems (Win 3x Win95-98)  still ran on top of DOS which meant that these graphical systems still referred the underlying DOS system to carry out operations and therefore Windows itself can be described as a shell program itself. From Windows XP onwards DOS no longer ran underneath Windows and if the user wished (as we do with QBasic) to run a DOS program Windows runs an emulated version called a virtual machine which is why some simple DOS programs run so slowly on some machines. As such Batch programming is a thing of the past and  was never meant to be a fully fledged language however when text based systems were the only option, navigating through the file system, deleting files and starting programs could only be done using DOS commands.  And without the batch file language and the AUTOEXEC.BAT file facility many happy hours would have been spent by the novice user simply trying to get the system set up to do anything useful at all. Eventually Microsoft developed Visual Basic Script that was adopted on the web and became popular with system administrators wanting to a more powerful way to automate administrative server operations.

HMTL Stands for Hypertext Mark Up Language which is denoted by the .HTM extension on the end of web page files. Like Batch File HTML cannot be considered a programming language but also like batch file languages contain surprising amounts of functionality.HTML is in fact a text and image formatting language that is displayed in web browsers such as one you are viewing this page on right now. It was invented by a by Tim Berners Lee at CERN to enable scientists to disseminate information between themselves and has since been adopted by the web as the main base system for disseminating information. Besides presenting information the most useful of the original features of HTML is the use of Hyperlinks that allow readers to open other web documents or go to other parts of the same text based on a hyper linked word. added functionality has been incorporated into the web environment with the ability of web browsers to run Java Script,  Microsoft's JScript  and Java which does offer web authors the ability to run applications and offer functionality outside the bounds of HTML such as dynamic websites and enhanced user interfaces. Java Script, although using similar C++ syntax  as Java are not related and were developed by two different companies Netscape developing Java Script and Sun Micro systems developing Java. Java Script is not  tightly structured language and offers greater freedom for web designers.

Visual Basic is the successor to earlier DOS based IDE systems such as  QBasic and has been designed for the novice and expert alike to program  simple but powerful programs using GUI (Graphical User Interface) in and IDE (Integrated Development Environment). This is achieved using an environment where ready made controls such as text boxes option and command buttons can be dragged onto a form window then formatted before or during execution in response to some event. While in development code can be written into controls for functionality. Visual basic is an event driven programming environment so when an event happens such as when a user clicks a button with the mouse that event triggers certain other events. In the case of a button  being pressed may only involve the button graphic changing to give the appearance that of being pressed  but if the button has some user code written into it this will be executed at the same time.  Visual basic has been designed to allow connectivity to databases using Data Access Objects and latter versions include functionality for the creation of ActiveX controls  that allow reusable controls for use in programing environments other than visual basic and can be used on the web as they are supported by Microsoft Explorer V3 or later.  

Some programming environments have been specifically written for games production called games engines that contain facilities for Graphics, sound, movement, collision, networking and so on while other environments are more specific to office application development. Java was developed specifically for the internet and for this reason it handles the question of interpretation and compilation in a slightly different way. The programmers of Java wanted a system that offered the speed of a compiled language and the platform independence of an interpreted language. So Java was developed to be compiled to an intermediate  level between compiled and interpreted then run on the JVM (Java Virtual Machine) platform. Once the JVM program was distributed for a given type of sytem Java programs could be run anywhere and everywhere. For this reason it was called a WORA (Write Once Run Anywhere) programming environment and has been called the most influential programming language of the twentieth century. Incidentally Java has a very C++ feel to it but stops short of  so much of the low level control however it maintains much of the structure that C++ is so revered for.  Another reason for the success of Java was the decision by its developers Sun Micro Systems to Re license Java under a GNU License that allowed none affiliated programmers access to source codes which led to further development and acceptance.