Chapter 1 - Getting Started WHAT IS AN IDENTIFIER? Before you can do anything in any language, you must at least know how you name an identifier. An identifier is used for any variable, function, data definition, etc. In the programming language C, an identifier is a combination of alphanumeric characters, the first being a letter of the alphabet or an underline, and the remaining being any letter of the alphabet, any numeric digit, or the underline. In the case of Turbo C, a dollar sign is permitted but not as the first character of an identifier. It should be pointed out that even though a dollar sign is permitted by the Turbo C compiler, it is not used anywhere in this tutorial since it is not in general use by C programmers, and is not even allowed by most compilers. If you do not plan to write any portable code, you can use it at will if you feel it makes your code more readable. Two rules must be kept in mind when naming identifiers. 1. The case of alphabetic characters is significant. Using "INDEX" for a variable is not the same as using "index" and neither of them is the same as using "InDeX" for a variable. All three refer to different variables. 2. As Turbo C is defined, up to 32 significant characters can be used and will be considered significant. If more than 32 are used, they will be ignored by the compiler. You can reduce the number used to anything less than 32 if you desire as a compiler option. You should not do this for the duration of your study of this tutorial as you could get some odd compiler diagnostics. WHAT ABOUT THE UNDERLINE? Even though the underline can be used as part of a variable name, and adds greatly to the readability of the resulting code, it seems to be used very little by experienced C programmers. It adds greatly to the readability of a program to use descriptive names for variables and it would be to your advantage to do so. Pascal programmers tend to use long descriptive names, but most C programmers tend to use short cryptic names. Most of the example programs in this tutorial use very short names for that reason. Any computer program has two entities to consider, the data, and the program. They are highly dependent on one another and careful planning of both will lead to a well Page 4 Chapter 1 - Getting Started planned and well written program. Unfortunately, it is not possible to study either completely without a good working knowledge of the other. For this reason, this tutorial will jump back and forth between teaching methods of program writing and methods of data definition. Simply follow along and you will have a good understanding of both. Keep in mind that, even though it seems expedient to sometimes jump right into the program coding, time spent planning the data structures will be well spent and the final program will reflect the original planning. HOW THIS TUTORIAL IS WRITTEN As you go through the example programs, you will find that every program is complete. There are no program fragments that could be confusing. This allows you to see every requirement that is needed to use any of the features of Turbo C as they are presented. Some tutorials I have seen give very few, and very complex examples. They really serve more to confuse the student. This tutorial is the complete opposite because it strives to cover each new aspect of programming in as simple a context as possible. This method, however, leads to a lack of knowledge in how the various parts are combined. For that reason, the last chapter is devoted entirely to using the features taught in the earlier chapters. It will illustrate how to put the various features together to create a usable program. They are given for your study, and are not completely explained. Enough details of their operation are given to allow you to understand how they work after you have completed all of the previous lessons. At this point, you should load and run FIRSTEX.C if you have not yet done so, to see that the Turbo C compiler is properly loaded and operating. If you have any problems, see the COMPILER.DOC file for help in properly setting up your computer to compile and run Turbo C programs. A DISCUSSION OF SOME OF THE FILES LIST.EXE This file will list the source files for you with line numbers and filename. To use it, simply type "LIST" followed by the appropriate filename. Type LIST FIRSTEX.C now for an example. The C source code is given later in Chapter 14 along with a brief description of its operation. After you have completed your study of Turbo C, you will have the ability to read and understand the source code for this program. Page 5 Chapter 1 - Getting Started PRINTALL.BAT This is a batch file that will call the above LIST.EXE file once for each of the example C programs, printing all of the files out. If you want a hardcopy of all of the files, enter PRINTALL and watch as your printer fills about 150 sheets of paper with C programs. Page 6