You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
25 lines
1.3 KiB
25 lines
1.3 KiB
== The classic example
|
|
The classic example program for the C language is Hello World. Here is the source code for our version of the program:
|
|
|
|
[source,c]
|
|
----
|
|
#include <stdio.h>
|
|
|
|
int
|
|
main (void)
|
|
{
|
|
printf ("Hello, world!\n");
|
|
return 0;
|
|
}
|
|
----
|
|
|
|
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'.
|
|
|
|
Note that if a file with the same name as the executable file already exists in the current directory it will be overwritten.
|
|
|
|
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++.
|
|
|
|
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.
|
|
|
|
|
|
|
|
|