What is a set of rules and symbols required to operate a computer?
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Here is a list of all the reserved words in Standard C++, and a few predefined identifiers for the sake of comparison. Show There is a distinction between reserved words and predefined identifiers, which are sometimes collectively referred to as keywords. Nevertheless, be aware that the terminology is nonstandard. As an illustration, some authors use keyword in the same sense that others use reserved word. C++ Reserved WordsThe reserved words of C++ may be conveniently placed into several groups. In the first group, we put those that were also present in the C programming language and have been carried over into C++. There are 32 such reserved words:auto const double float int short struct unsigned break continue else for long signed switch void case default enum goto register sizeof typedef volatile char do extern if return static union whileThere are another 30 reserved words that were not in C, are therefore new to C++: asm dynamic_cast namespace reinterpret_cast try bool explicit new static_cast typeid catch false operator template typename class friend private this using const_cast inline public throw virtual delete mutable protected true wchar_tThe following 11 C++ reserved words are not essential when the standard ASCII character set is being used, but they have been added to provide more readable alternatives for some of the C++ operators, and also to facilitate programming with character sets that lack characters needed by C++. and bitand compl not_eq or_eq xor_eq and_eq bitor not or xor Note that your particular compiler may not be completely up-to-date, which means that some (and possibly many) of the reserved words in the preceding two groups may not yet be implemented. Some Predefined IdentifiersBeginning C++ programmers are sometimes confused by the difference between the two terms reserved word and predefined identifier, and some potential for confusion. One of the difficulties is that some keywords that one might "expect" to be reserved words are not. The keyword main is a prime example, and others include things like the endl manipulator and other keywords from the vast collection of C++ libraries. For example, you could declare a variable called main inside your main function, initialize it, and then print out its value (but ONLY do that to verify that you can!). On the other hand, you could not do this with a variable named else. The difference is that else is a reserved word, while main is "only" a predefined identifier. An important point before we proceed: You will not be a programmer when you finish reading this chapter or even when you finish reading the final chapter. Programming proficiency takes practice and training beyond the scope of this book. However, you will become acquainted with how programmers develop solutions to a variety of problems. In general, the programmer's job is to convert problem solutions into instructions for the computer. That is, the programmer prepares the instructions of a computer program and runs those instructions on the computer, tests the program to see if it is working properly, and makes corrections to the program. The programmer also writes a report on the program. These activities are all done for the purpose of helping a user fill a need, such as paying employees, billing customers, or admitting students to college. The programming activities just described could be done, perhaps, as solo activities, but a programmer typically interacts with a variety of people. For example, if a program is part of a system of several programs, the programmer coordinates with other programmers to make sure that the programs fit together well. If you were a programmer, you might also have coordination meetings with users, managers, systems analysts, and with peers who evaluate your work-just as you evaluate theirs. Let us turn to the programming process. Developing a program involves steps similar to any problem-solving task. There are five main ingredients in the programming process:
Let us discuss each of these in turn.
Suppose that, as a programmer, you are contacted because your services are needed. You meet with users from the client organization to analyze the problem, or you meet with a systems analyst who outlines the project. Specifically, the task of defining the problem consists of identifying what it is you know (input-given data), and what it is you want to obtain (output-the result). Eventually, you produce a written agreement that, among other things, specifies the kind of input, processing, and output required. This is not a simple process. Figure 1: Flow Chart Symbols and Flow Chart For Mailing Letter  Pseudocode is an English-like nonstandard language that lets you state your solution with more precision than you can in plain English but with less precision than is required when using a formal programming language. Pseudocode permits you to focus on the program logic without having to be concerned just yet about the precise syntax of a particular programming language. However, pseudocode is not executable on the computer. We will illustrate these later in this chapter, when we focus on language examples. As the programmer, your next step is to code the program-that is, to express your solution in a programming language. You will translate the logic from the flowchart or pseudocode-or some other tool-to a programming language. As we have already noted, a programming language is a set of rules that provides a way of instructing the computer what operations to perform. There are many programming languages: BASIC, COBOL, Pascal, FORTRAN, and C are some examples. You may find yourself working with one or more of these. We will discuss the different types of languages in detail later in this chapter. Although programming languages operate grammatically, somewhat like the English language, they are much more precise. To get your program to work, you have to follow exactly the rules-the syntax-of the language you are using. Of course, using the language correctly is no guarantee that your program will work, any more than speaking grammatically correct English means you know what you are talking about. The point is that correct use of the language is the required first step. Then your coded program must be keyed, probably using a terminal or personal computer, in a form the computer can understand. One more note here: Programmers usually use a text editor, which is somewhat like a word processing program, to create a file that contains the program. However, as a beginner, you will probably want to write your program code on paper first. Some experts insist that a well-designed program can be written correctly the first time. In fact, they assert that there are mathematical ways to prove that a program is correct. However, the imperfections of the world are still with us, so most programmers get used to the idea that their newly written programs probably have a few errors. This is a bit discouraging at first, since programmers tend to be precise, careful, detail-oriented people who take pride in their work. Still, there are many opportunities to introduce mistakes into programs, and you, just as those who have gone before you, will probably find several of them. Eventually, after coding the program, you must prepare to test it on the computer. This step involves these phases: Documenting is an ongoing, necessary process, although, as many programmers are, you may be eager to pursue more exciting computer-centered activities. Documentation is a written detailed description of the programming cycle and specific facts about the program. Typical program documentation materials include the origin and nature of the problem, a brief narrative description of the program, logic tools such as flowcharts and pseudocode, data-record descriptions, program listings, and testing results. Comments in the program itself are also considered an essential part of documentation. Many programmers document as they code. In a broader sense, program documentation can be part of the documentation for an entire system. The wise programmer continues to document the program throughout its design, development, and testing. Documentation is needed to supplement human memory and to help organize program planning. Also, documentation is critical to communicate with others who have an interest in the program, especially other programmers who may be part of a programming team. And, since turnover is high in the computer industry, written documentation is needed so that those who come after you can make any necessary modifications in the program or track down any errors that you missed. There is a shortage of qualified personnel in the computer field. Before you join their ranks, consider the advantages of the computer field and what it takes to succeed in it. The Joys of the Field What It Takes Open Doors Programming languages are said to be "lower" or "higher," depending on how close they are to the language the computer itself uses (Os and 1s = low) or to the language people use (more English-like-high). We will consider five levels of language. They are numbered 1 through 5 to correspond to levels, or generations. In terms of ease of use and capabilities, each generation is an improvement over its predecessors. The five generations of languages are
Let us look at each of these categories. Machine Language Assembly Languages The programmer who uses an assembly language requires a translator to convert the assembly language program into machine language. A translator is needed because machine language is the only language the computer can actually execute. The translator is an assembler program, also referred to as an assembler. It takes the programs written in assembly language and turns them into machine language. Programmers need not worry about the translating aspect; they need only write programs in assembly language. The translation is taken care of by the assembler. Although assembly languages represent a step forward, they still have many disadvantages. A key disadvantage is that assembly language is detailed in the extreme, making assembly programming repetitive, tedious, and error prone. This drawback is apparent in the program in Figure 2. Assembly language may be easier to read than machine language, but it is still tedious. High-Level Languages These so-called third-generation languages spurred the great increase in data processing that characterized the 1960s and 1970s. During that time the number of mainframes in use increased from hundreds to tens of thousands. The impact of third-generation languages on our society has been enormous. Of course, a translator is needed to translate the symbolic statements of a high-level language into computer-executable machine language; this translator is usually a compiler. There are many compilers for each language and one for each type of computer. Since the machine language generated by one computer's COBOL compiler, for instance, is not the machine language of some other computer, it is necessary to have a COBOL compiler for each type of computer on which COBOL programs are to be run. Keep in mind, however, that even though a given program would be compiled to different machine language versions on different machines, the source program itself-the COBOL version-can be essentially identical on each machine. Some languages are created to serve a specific purpose, such as controlling industrial robots or creating graphics. Many languages, however, are extraordinarily flexible and are considered to be general-purpose. In the past the majority of programming applications were written in BASIC, FORTRAN, or COBOL-all general-purpose languages. In addition to these three, another popular high-level language is C, which we will discuss later. Very High-Level Languages Definition Characteristics Productivity TABLE FILE SALES SUM UNITS BY MONTH BY CUSTOMER BY PRODUCT ON CUSTOMER SUBTOTAL PAGE BREAK ENDEven though some training is required to do even this much, you can see that it is pretty simple. The third-generation language COBOL, however, typically requires over 500 statements to fulfill the same request. If we define productivity as producing equivalent results in less time, then fourth-generation languages clearly increase productivity. Downside Benefits
It was not long ago that few people believed that 4GLs would ever be able to replace third-generation languages. These 4GL languages are being used, but in a very limited way. Query Languages Natural Languages Natural languages are sometimes referred to as knowledge-based languages, because natural languages are used to interact with a base of knowledge on some subject. The use of a natural language to access a knowledge base is called a knowledge-based system. Consider this request that could be given in the 4GL Focus: "SUM ORDERS BY DATE BY REGION." If we alter the request and, still in Focus, say something like "Give me the dates and the regions after you've added up the orders," the computer will spit back the user-friendly version of "You've got to be kidding" and give up. But some natural languages can handle such a request. Users can relax the structure of their requests and increase the freedom of their interaction with the data. Here is a typical natural language request: REPORT THE BASE SALARY, COMMISSIONS AND YEARS OF SERVICE BROKEN DOWN BY STATE AND CITY FOR SALESCLERKS IN NEW JERSEY AND MASSACHUSETTS. You can hardly get closer to conversational English than that. An example of a natural language is shown in Figure 3. Natural languages excel at easy data access. Indeed, the most common application for natural languages is interacting with databases. How do you choose the language with which to write your program? There are several possibilities:
Figure 4: Flow Chart For Averaging Numbers This chapter will present programs written in some of these languages. You will also see output produced by each program. Each program is designed to find the average of three numbers; the resulting average is shown in the sample output matching each program. Since all programs perform the same task, you will see some of the differences and similarities among the languages. We do not expect you to understand these programs; they are here merely to let you glimpse each language. Figure 4 presents the flowchart and pseudocode for the task of averaging numbers. As we discuss each language, we will provide a program for averaging numbers that follows the logic shown in this figure. FORTRAN: The First High-Level Language FORTRAN is noted for its brevity, and this characteristic is part of the reason why it remains popular. This language is very good at serving its primary purpose, which is execution of complex formulas such as those used in economic analysis and engineering. Although in the past it was considered limited in regard to file processing or data processing, its capabilities have been greatly improved. Not all programs are organized in the same way. Organization varies according to the language used. In many languages (such as COBOL), programs are divided into a series of parts. FORTRAN programs are not composed of different parts (although it is possible to link FORTRAN programs together); a FORTRAN program consists of statements one after the other. Different types of data are identified as the data is used. Descriptions for data records appear in format statements that accompany the READ and WRITE statements. Figure 5 shows a FORTRAN program and a sample output from the program. COBOL: The Language of Business The U.S. government offered encouragement by insisting that anyone attempting to win government contracts for computer-related projects had to use COBOL. The American National Standards Institute first standardized COBOL in 1968 and, in 1974, issued standards for another version known as ANSI-COBOL. After more than seven controversial years of industry debate, the standard known as COBOL 85 was approved, making COBOL a more usable modern-day software tool. The principal benefit of standardization is that COBOL is relatively machine independent- that is, a program written for one type of computer can be run with only slight modifications on another type for which a COBOL compiler has been developed. COBOL is very good for processing large files and performing relatively simple business calculations, such as payroll or interest. A noteworthy feature of COBOL is that it is English-like-far more so than FORTRAN or BASIC. The variable names are set up in such a way that, even if you know nothing about programming, you can still understand what the program does. For example: IF SALES-AMOUNT IS GREATER THAN SALES-QUOTA COMPUTE COMMISSION = MAX-RATE * SALES-AMOUNT ELSE COMPUTE COMMISSION = MIN-RATE * SALES-AMOUNT. Once you understand programming principles, it is not too difficult to add COBOL to your repertoire. COBOL can be used for just about any task related to business programming; indeed, it is especially suited to processing alphanumeric data such as street addresses, purchased items, and dollar amounts-the data of business. However, the feature that makes COBOL so useful-its English-like appearance and easy readability-is also a weakness because a COBOL program can be incredibly verbose. A programmer seldom knocks out a quick COBOL program. In fact, there is hardly such a thing as a quick COBOL program; there are just too many program lines to write, even to accomplish a simple task. For speed and simplicity, BASIC, FORTRAN, and Pascal are probably better bets. As you can see in Figure 6, a COBOL program is divided into four parts called divisions. The identification division identifies the program by name and often contains helpful comments as well. The environment division describes the computer on which the program will be compiled and executed. It also relates each file of the program to the specific physical device, such as the tape drive or printer, that will read or write the file. The data division contains details about the data processed by the program, such as type of characters (whether numeric or alphanumeric), number of characters, and placement of decimal points. The procedure division contains the statements that give the computer specific instructions to carry out the logic of the program. It has been fashionable for some time to criticize COBOL: It is old-fashioned, cumbersome, and inelegant. In fact, some companies, devoted to fast, nimble program development, are converting to the more trendy language C. But COBOL, with more than 30 years of staying power, is still famous for its clear code, which is easy to read and debug. BASIC: For Beginners and Others The primary feature of BASIC is one that may be of interest to many readers of this book: BASIC is easy to learn, even for a person who has never programmed before. Thus, the language is used often to train students in the classroom. BASIC is also used by non-programming people, such as engineers, who find it useful in problem solving. For many years, BASIC was looked down on by "real programmers," who complained that it had too many limitations and was not suitable for complex tasks. Newer versions, such as Microsoft's QuickBASIC, include substantial improvements. An example of a BASIC program and its output are shown in Figure 7. Pascal: The Language of Simplicity The foremost feature of Pascal is that it is simpler than other languages -it has fewer features and is less wordy than most. In addition to the popularity of Pascal in college computer science departments, the language has also made large inroads in the personal computer market as a simple yet sophisticated alternative to BASIC. Over the years new versions have improved on the original capabilities of Pascal. Today, Borland's Turbo Pascal leads the Pascal world because its designers eliminated most of the drawbacks of the original Pascal. Turbo Pascal is used by the business community and is often the choice of nonprofessional programmers who need to write their own programs. Ada: Named for the Countess Widespread use of Ada is considered unlikely by many experts. Although there are many reasons for this (the military services, for instance, have different levels of enthusiasm for it), probably its size- which may hinder its use on personal computers-and complexity are the greatest barriers. Although the Department of Defense is a market in itself, Ada has not caught on to the extent that Pascal and C have, especially in the business community. C, C++, Java, and Javascript Although C is simple and elegant, it is not simple to learn. It was developed for gifted programmers, and the learning curve may be steep. Straightforward tasks may be solved easily in C, but complex problems require mastery of the language. An interesting side note is that the availability of C on personal computers has greatly enhanced the value of personal computers for budding software entrepreneurs. A cottage software industry can use the same basic tool-the language C-used by established software companies such as Microsoft and Borland. Today C is has been replaced by its enhanced cousin, C++. C++ in turn is being challenged by web-aware languages like Java and Javascript, that look and act a lot like C++, but add features to support working with networked computers, among other things. What are operation symbols in computer programming?In mathematics and computer programming, an operator is a character that represents a specific mathematical or logical action or process. For instance, "x" is an arithmetic operator that indicates multiplication, while "&&" is a logical operator representing the logical AND function in programming.
What are the 4 types of code?Common styles are imperative, functional, logical, and object-oriented languages. Programmers can choose from these coding language paradigms to best-serve their needs for a specific project.
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