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24 lines
1.2 KiB
24 lines
1.2 KiB
The classic example program for the C language is Hello World. Here is the source code for our version of the program:
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[source,c]
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----
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#include <stdio.h>
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int
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main (void)
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{
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printf ("Hello, world!\n");
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return 0;
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}
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----
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This compiles the source code in 'hello.c' to machine code and stores it in an executable file 'hello'. The output file for the machine code is specified using the -o option. This option is usually given as the last argument on the command line. If it is omitted, the output is written to a default file called 'a.out'.
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Note that if a file with the same name as the executable file already exists in the current directory it will be overwritten.
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The option -Wall turns on all the most commonly-used compiler warnings---it is recommended that you always use this option! There are many other warning options which will be discussed in later chapters, but -Wall is the most important. GCC will not produce any warnings unless they are enabled. Compiler warnings are an essential aid in detecting problems when programming in C and C++.
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In this case, the compiler does not produce any warnings with the -Wall option, since the program is completely valid. Source code which does not produce any warnings is said to compile cleanly.
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