Memory and Computing Power

The amount of RAM in a computer can have a profound effect on the computer's power. More RAM means the computer can use bigger, more powerful programs, and those programs can access bigger data files.

More RAM also can make the computer run faster. The computer does not necessarily have to load an entire program into memory to run it. However, the greater the amount of the program that fits into memory, the faster the program runs. For example, a PC with 16 MB of RAM is able to run Microsoft Windows 98, even though the program actually occupies about 195 MB of disk storage space. When you run Windows, the program does not need to load all its files into memory to run properly. It loads only the most essential parts into memory. When the computer needs access to other parts of the program on the disk, it can unload, or swap out, nonessential parts from RAM to the hard disk. Then the computer can load, or swap in, the program code or data it needs. While this is an effective method for managing a limited amount of memory, it can result in slow system performance because the CPU, memory, and disk are continuously occupied with the swapping process. If your PC has 64 MB of RAM (or more), you will notice a dramatic difference in how fast Microsoft Windows 98 runs because the CPU will need to swap program instructions between RAM and the hard disk much less often.

If you own a PC and decide that it needs more RAM, you should be able to buy more, open up your computer, and plug it in. (Some newer PCs come "stuffed" with all the RAM they can hold, making it difficult to upgrade.) In some computers, chips are usually grouped together on small circuit boards called single in-line memory modules (SIMMs) or dual in-line memory modules (DIMMs). Each SIMM or DIMM can hold between 1 MB and 64 MB of RAM and connects to the motherboard with 30-pin, 72-pin, or 168-pin connections. In newer computers both these modules are replaced by DDR и DDR II types that can hold up to 2 Gb of RAM.

The cost of upgrading the memory of a computer has actually gone down, so upgrading RAM is often the most cost-effective way to get more speed from your computer.

UNIT 6. Programming

Visual Programming

The object-oriented, event-driven environment of modern programming has changed how information flows through a program. It has given the control of a program's actions to the user.

In the past, programmers created program-centered processing, in which the flow of action was dictated totally by the program. Even in an interactive program, where information flowed in two directions, the central focus was always the program with its preset logic and processing path.

Object-oriented, event-driven programming has changed the programming environment by putting the user in control. The user now chooses which actions are used, chooses how each action is started, and directs the flow of the entire activity. As a result, the programmer cannot presume which objects the user will choose or the order in which they will be chosen.

Event-driven programs are designed around the interface options available to the user. An event is initiated by the user. When the user clicks an icon with the mouse, presses the Enter key, or moves the pointer on the screen, an event occurs. Each event causes an object to gather its data, structure it, and process it.

Event-driven programs are created in a visual WYSIWYG environment that uses a visual programming language (VPL). A VPL allows the programmer to create visually the graphical images the user will see and use.

The programmer combines graphical icons, forms, diagrams, and expressions to create two-or three-dimensional programs to run in a graphical user environment.

Some of the most commonly used visual languages are Prograph CPX for the Apple Macintosh, Microsoft's Visual Basic, and Visual C++ for the Windows environment. Visual programs for Java and scripting environments – JavaScript and VBScript – have recently emerged. These languages use graphical objects, such as icons, forms, or diagrams, to create programs that run in a visual environment. Programming in a visual language involves placing controls in the graphical presentation so that users can interact with them. Controls are the various tools through which the user can enter data, begin a process, or indicate a choice.

The Open dialog box (found in nearly all Windows-based programs), for example, is filled with various types of controls, such as buttons, lists, text boxes, and more. Placing controls on a graphical environment typically is done using the drag-and-drop technique. The programmer chooses the control to be made available to the user for an event and places it on the window form. Usually, the available controls are contained in a menu, list, or dialog box for the programmer's ease of access and use, as in the Visual Basic toolbox.

Visual programming is much easier for the programmer because it is based on how a programmer (and the user) sees items on the screen rather than on the structure of the program. As in many other areas of computer software, the visual interface is making highly complex functions accessible to the everyday user.

Third-generation Programming Languages (Part I)

There are many higher-level languages and there is no reason why you should have to know the details of each. However, it is always helpful to know a little about the more common languages you may hear about in programming circles. Some of the fading third-generation languages include the following:

FORTRAN (FORmula TRANslator). FORTRAN was designed specifically for mathematical and engineering programs. FORTRAN has not been widely used with personal computers. Instead, FORTRAN remains a common language on mainframe systems, especially those used for research and education.

COBOL (COmmon Business Oriented Language). COBOL was developed in 1960 by a government-appointed committee to help solve the problem of incompatibilities among computer manufacturers. Although COBOL was once popular, especially on mainframe systems, it has lost some of its following over the past ten years.

BASIC (Beginner's All-Purpose Symbolic Instruction Code). BASIC was developed in the mid-1960s, mainly as a tool for teaching programming to students. Because of its simplicity, BASIC quickly became popular. When the use of personal computers became widespread, it was the first high-level language to be implemented on these new machines. One early version of BASIC shipped on the newly popular PCs was GWBASIC. As you might have guessed, GW stands for "Gates, William" so you can see how influential Bill Gates was in the early development of PC software. Today, popular examples of BASIC include Microsoft's Visual Basic, Visual Basic for Applications (the scripting language behind Microsoft Office), and VBScript (which is common in many Web pages).

Pascal. Named after the seventeenth-century French inventor Blaise Pascal, Pascal was intended in the early 1970s to overcome the limitations of other programming languages and to demonstrate the benefits of structured programming. More recently, developers have taken Pascal a step further, and it is now well-known for its implementation of object-oriented principles of programming.

Third-generation Programming Languages (Part II)

Unlike such third-generation languages as FORTRAN, COBOL, BASIC, Pascal, the following languages still have a thriving following and a bright future:

C. Often regarded as the thoroughbred of programming languages, C produces programs with fast and efficient executable code. C is also a powerful language. With it, you can make a computer do just about anything it is possible for a computer to do. Because of this programming freedom, C is extremely popular with professional developers, although it is now being replaced by C++.

C++. C++ is the object-oriented implementation of C. Like C, C++ is an extremely powerful and efficient language. Learning C++ means learning everything about C and then learning about object-oriented programming and its implementation with C++. Nevertheless, more C programmers move to C++ every year, and the newer language has replaced C as the language of choice among software development companies.

Java. Java is an object-oriented programming environment for creating cross-platform programs. When the Internet became popular in the mid-1990s, Java's developer, Sun Microsystems, redeveloped Java to become a programming environment for the Web. With Java, Web designers can create interactive and dynamic programs (called applets) for Web pages. Essentially, a Java program is a self-contained, semicompiled function that makes no reference to outside code or operating system functions. Thus, Java code is fully compatible with most any computer and operating system. To create Java code, a developer writes the applet and then compiles it into bytecode. To run the Java applet, a user accesses the bytecode, perhaps over the Internet. Then, using a Java virtual machine, the client PC converts the bytecode into machine code appropriate to that particular computer.

ActiveX. Microsoft's answer to Java is ActiveX. ActiveX code creates self-contained functions similar to Java applets that may be accessed and executed by any other ActiveX-compatible program on any ActiveX system or network. At present, ActiveX is implemented on Windows 9x, Windows NT, and Macintosh systems, and there are plans for supporting UNIX also.

Of the third-generation languages, Java is probably the most important for the future development of PCs and the Internet. In fact, some developers see Java as a way of redefining the PC itself. By replacing the current expensive and platform-defining CPU with a cheap Java-decoding microchip, developers can create a machine that gets all of its software from Java servers on the Internet. To use such a machine, you would load a Web browser (also written in Java), connect to the Internet, and access Java programs for all of your software needs. If this prediction comes true, then all PCs will be both inexpensive and fully compatible.

Fourth-generation Programming Languages

Fourth-generation languages include the following:

Visual Basic (VB). Visual Basic is the newest incarnation of BASIC from Microsoft. VB supports object-oriented features and methods. With this language, programmers can build programs in a visual environment. Visual Basic offers several toolbars with lots of tools to assist the programmer in designing the code visually, as well as a window for editing code directly.

VisualAge. VisualAge is a family of IBM development tools that allows the user to create entire Java- and Web-based systems using drag-and-drop development techniques.

Authoring Environments. Authoring environments are special-purpose programming tools for creating multimedia, computer-based training, Web pages, and so forth. One example of an authoring environment is Macromedia Director (which uses the Lingo scripting language). You can use it to create multimedia titles combining music clips, text, animation, graphics, and so forth. As with other visual development environments, much of the code is written automatically. However, most of the robust authoring environments also include their own languages, called scripting languages, that provide tools for added control over the final product. The programs used to create World Wide Web pages fall into another category of tools that are often lumped together with authoring environments. Some of these programs include Microsoft FrontPage, Netscape Visual JavaScript, and NetObjects Fusion.

Date: 2015-12-11; view: 796