Compilation and Execution

Once you have written the program you need to type it and instruct the machine to execute it. To type your C program you need another program called Editor. Once the program has been typed it needs to be converted to machine language (0s and 1s) before the machine can execute it. To carry out this conversion we need another program called Compiler. Compiler vendors provide an Integrated Development Environment (IDE) which consists of an Editor as well as the Compiler.

There are several such IDEs available in the market targeted towards different operating systems. For example, Turbo C, Turbo C++ and Microsoft C are some of the popular compilers that work under MS-DOS; Visual C++ and Borland C++ are the compilers that work under Windows, whereas gcc compiler works under Linux. Note that Turbo C++, Microsoft C++ and Borland C++ software also contain a C compiler bundled with them. If you are a beginner you would be better off using a simple compiler like Turbo C or Turbo C++. Once you have mastered the language elements you can then switch over to more sophisticated compilers like Visual C++ under Windows or gcc under Linux. Most of theprograms in this book would work with all the compilers. Wherever there is a deviation I would point it out that time.
Assuming that you are using a Turbo C or Turbo C++ compiler here are the steps that you need to follow to compile and execute your first C program… 

(a) Start the compiler at C> prompt. The compiler (TC.EXE is usually present in C:\TC\BIN directory). 

(b) Select New from the File menu.
(c) Type the program.
(d) Save the program using F2 under a proper name (say Program1.c).
(e) Use Ctrl + F9 to compile and execute the program.
(f) Use Alt + F5 to view the output.

Note that on compiling the program its machine language equivalent is stored as an EXE file (Program1.EXE) on the disk. This file is called an executable file. If we copy this file to another machine we can execute it there without being required to recompile it. In fact the other machine need not even have a compiler to be able to execute the file.

A word of caution! If you run this program in Turbo C++ compiler, you may get an error — “The function printf should have a prototype”. To get rid of this error, perform the following steps and then recompile the program.

(a) Select ‘Options’ menu and then select ‘Compiler | C++ Options’. In the dialog box that pops up, select ‘CPP always’ in the ‘Use C++ Compiler’ options.

(b) Again select ‘Options’ menu and then select ‘Environment | Editor’. Make sure that the default extension is ‘C’ rather than ‘CPP’.