With the increasing popularity of object-oriented programming, C is being rapidly replaced as "the" programming language by C++, a superset of the C language that uses an entirely different set of programming concepts, and by Java, a language similar to but simpler than C++, that was designed for use in distributed networks.

   Depending on the public key infrastructure implementation, the certificate includes the owner's public key, the expiration date of the certificate, the owner's name, and other information about the public key owner.

   Microsoft uses cabinet files in distributing its own products, such as PowerPoint, Microsoft Office for Windows, and Microsoft Money. Cabinet files save space and time during software distribution. They are decompressed during installation. Large files can be compressed and included in more than one cabinet file, each of which logically points to the next file, with all contained in a logical folder.

   Development accountability for cabinet files is ensured by providing a signed digital certificate with the cabinet file. One "signature" covers all the files in a cabinet file. Cabinet files are created using Lempel-Ziv compression.

   Cache memory is sometimes described in levels of closeness and accessability to the microprocessor. A level-1 (L1) cache is on the same chip as the microprocessor. (For example, the PowerPC 601 processor has a 32 kilobytes level-1 cache built into its chip.) Level-2 cache is usually a separate static RAM (SRAM) chip. The main RAM is usually a dynamic RAM (DRAM) chip. SRAM does not have to be electromagnetically refreshed as DRAM does, and is therefore more expensive. A popular SRAM (or cache memory) size is 1048 kilobytes (1 megabyte). Typical DRAM sizes are 4 megabytes to 32 megabytes.

   In addition to cache memory, one can think of RAM itself as a cache of memory for hard disk storage since all of RAM's contents come from the hard disk initially when you turn your computer on and load the operating system (you are loading it into RAM) and later as you start new applications and access new data. RAM can also contain a special area called a disk cache that contains the data most recently read in from the hard disk.

   A WORM (write once, read many) device is used to write information to a master disk from which CD-ROM disks are replicated.

   In iCOMP Index 2.0 benchmark tests, the Celeron processor generally achieved about 70% of the performance of a comparable Pentium II. A Celeron 300 MHz had an iCOMP score of 226, while the Pentium II 300 MHz had an iCOMP score of 332. Intel is marketing the processor as a chip for the basic PC. They view it as providing performance good enough for home and business users doing word processing and Internet surfing. Power users and serious gamers will want to think about spending more for the Pentium II's top performance.

   If you are creating a Web site and want a CGI application to get control, you specify the name of the application in the URL that you code in an HTML file. This URL can be specified as part of the FORMS tags if you are creating a form. For example, you might code:

   <FORM METHOD=POST ACTION=http://www.mybiz.com/cgi-bin/formprog.pl>

and the server at "mybiz.com" would pass control to the CGI application called "formprog.pl" to record the entered data and return a confirmation message. (The ".pl" indicates a program written in Perl but other languages could have been used.)

   The common gateway interface provides a consistent way for data to be passed from the user's request to the application program and back to the user. This means that the person who writes the application program can makes sure it gets used no matter which operating system the server uses (PC, Macintosh, UNIX, OS/390, or others). It's simply a basic way for information to be passed from the Web server about your request to the application program and back again.

   Because the interface is consistent, a programmer can write a CGI application in a number of different languages. The most popular languages for CGI applications are: C, C++, Java, and Perl.

   An alternative to a CGI application is Microsoft's Active Server Page (ASP), in which a script embedded in a Web page is executed at the server before the page is sent.

   In a computer, the chassis houses the main electronic components, including the motherboard (with places to insert or replace microchips for the main and possibly specialized processors and random access memory (RAM) and places for adding optional adapters (for example, for audio or video capabilities). Typically, room is provided for a hard disk drive and a CD-ROM drive.

   The IBM PC chassis for its XT computers set an early de facto standard for a chassis configuration (sometimes referred to as the form factor). The desktop computer has since evolved through the AT model, the mini-AT, and the small-footprint PC. A later development was the vertical or tower chassis configuration, designed to be placed under a desk. The outer dimensions of a chassis are said to form its footprint.

   The term is not usually applied to mobile and notebook computers perhaps because the hardware components have to be more tightly integrated. Some communications devices such as terminal servers have chassis especially designed to handle many combinations of hardware add-ons. Such a chassis is described as modular.

   There are quite a few manufacturers of memory chips. Many special-purpose chips, known as ASICs (application-specific integrated circuits), are being made today for automobiles, home appliances, telephones, and other devices.

   A chip is manufactured from a silicon (or, in some special cases, a sapphire) wafer, which is first cut to size and then etched with circuits and electronic devices. The electronic devices use CMOS technology. The current stage of micro-integration is known as Very Large-Scale Integration (VLSI). A chip is also sometimes called an IC or integrated circuit.

   The client/server model has become one of the central ideas of network computing. Most business applications being written today use the client/server model. So does the Internet's main program, TCP/IP. In marketing, the term has been used to distinguish distributed computing by smaller dispersed computers from the "monolithic" centralized computing of mainframe computers. But this distinction has largely disappeared as mainframes and their applications have also turned to the client/server model and become part of network computing.

   In the usual client/server model, one server, sometimes called a daemon, is activated and awaits client requests. Typically, multiple client programs share the services of a common server program. Both client programs and server programs are often part of a larger program or application. Relative to the Internet, your Web browser is a client program that requests services (the sending of Web pages or files) from a Web server (which technically is called a Hypertext Transport Protocol or HTTP server) in another computer somewhere on the Internet. Similarly, your computer with TCP/IP installed allows you to make client requests for files from File Transfer Protocol (FTP) servers in other computers on the Internet.

   Other program relationship models included master/slave, with one program being in charge of all other programs, and peer-to-peer, with either of two programs able to initiate a transaction.

   In a computer, clock speed refers to the number of pulses per second generated by an oscillator that sets the tempo for the processor.   Clock speed is usually measured in MHz (megahertz, or millions of pulses per second). A typical computer clock runs at several hundred megahertz.  The clock speed is determined by a quartz-crystal circuit, similar to those used in radio communications equipment.

   Computer clock speed has been roughly doubling every year.  The Intel 8088, common in computers around the year 1990, ran at 4.77 MHz.  Today's computers run at several hundred megahertz. 

   Clock speed is one measure of computer "power," but it is not always directly proportional to the performance level.  If you double the speed of the clock, leaving all other hardware unchanged, you will not necessarily double the processing speed.  The type of microprocessor, the bus architecture, and the nature of the instruction set all make a difference.  In some applications, the amount of RAM (random access memory) is important, too.

   Some processors execute only one instruction per clock pulse.  More advanced processors can perform more than one instruction per clock pulse.  The latter type of processor will work faster at a given clock speed than the former type.   Similarly, a computer with a 32-bit bus will work faster at a given clock speed than a computer with a 16-bit bus.  For these reasons, there is no simplistic, universal relation among clock speed, "bus speed," and millions of instructions per second (MIPS).

   Excessive clock speed can be detrimental to the operation of a computer.   As the clock speed in a computer rises without upgrades in any of the other components, a point will be reached beyond which a further increase in frequency will render the processor unstable.  Some computer users deliberately increase the clock speed, hoping this alone will result in a proportional improvement in performance, and are disappointed when things don't work out that way.

   Since a cluster is a logical rather than a physical unit (it's not built into the hard disk itself), the size of a cluster can be varied. The maximum number of clusters on a hard disk depends on the size of a FAT table entry. Beginning with DOS 4.0, the FAT entries were 16 bits in length, allowing for a maximum of 65,536 clusters. Beginnning with the Windows 95 OSR2 service release, a 32-bit FAT entry is supported, allowing an entry to address enough clusters to support up to two terabytes of data (assuming the hard disk is that large!).

   The tradeoff in cluster size is that even the smallest file (and even a directory itself) takes up the entire cluster. Thus, a 10-byte file will take up 2,048 bytes if that's the cluster size. In fact, many operating systems set the cluster size default at 4,096 or 8,192 bytes. Until the FAT32 support in Windows 95 OSR2, the largest size hard disk that could be supported in a single partition was 512 megabytes. Larger hard disks could be divided into up to four partitions, each with a FAT capable of supporting 512 megabytes of clusters.

   2) In information technology marketing and infrastructure terminology, a cluster is a group of terminals or workstations attached to a common control unit or server or a group of several servers that share work and may be able to back each other up if one server fails. As of mid-1997, a two-server Windows NT cluster in which each system could back up the other in case of failure was priced at about $23,000. (The cost of writing failure scripts, considered to be a sophisticated programming task, would be extra.)

   COBOL was an effort to make a programming language that was like natural English, easy to write and easier to read the code after you'd written it. The earliest versions of the language, COBOL-60 and -61, evolved to the COBOL-85 standard sponsored by the Conference on Data Systems Languages (CODASYL).

   Since the year 2000 (Y2K) problem is common in many business applications and most of these are written in COBOL, programmers with COBOL skills have become sought after by major corporations and contractors. A number of companies have updated COBOL and sell development tools that combine COBOL programming with relational databases and the Internet.

COM includes COM+, DCOM, and ActiveX interfaces and programming tools.

   When executing (running), the compiler first parses (or analyzes) all of the language statements syntactically one after the other and then, in one or more successive stages or "passes", builds the output code, making sure that statements that refer to other statements are referenced correctly in the final code. Traditionally, the output of the compilation has been called object code or sometimes an object module. (Note that the term "object" here is not related to object-oriented programming.) The object code is machine code that the processor can process or "execute" one instruction at a time.

   More recently, the Java programming language, an object-oriented language, has introduced the possibility of compiling output (called bytecode) that can run on any computer system platform for which a Java virtual machine or bytecode interpreter is provided to convert the bytecode into instructions that can be executed by the actual hardware processor. Using this virtual machine, the bytecode can optionally be recompiled at the execution platform by a just-in-time (JIT) compiler.

   Traditionally in some operating systems, an additional step was required after compilation - that of resolving the relative location of instructions and data when more than one object module was to be run at the same time and they cross-refered to each other's instruction sequences or data. This process was sometimes called linkage editing and the output known as a load module.

   A compiler works with what are sometimes called 3GL, 4GL, and 5GL languages. An assembler works on programs written using a processor's assembler language.

   A related programming language, Java, is based on C++ but optimized for the distribution of program objects in a network such as the Internet. It is somewhat simpler than C++ and has characteristics that give it other advantages over C++.

For those learning object-oriented programming, MIT offers an Introduction to Object-Oriented Programming Using C++.

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