2.4. Building software from Natively Compiled Code

This section shows how to build the cello.c program written in the C language into an executable.

cello.c

#include <stdio.h>

int main(void) {
    printf("Hello World\n");
    return 0;
}

If you want to build the cello.c program manually, use this procedure:

Procédure

Invoke the C compiler from the GNU Compiler Collection to compile the source code into binary:
```
gcc -g -o cello cello.c
```
Execute the resulting output binary cello:
```
$ ./cello
Hello World
```

Large-scale software commonly uses automated building that is done by creating the Makefile file and then running the GNU make utility.

If you want to use the automated building to build the cello.c program, use this procedure:

Procédure

To set up automated building, create the Makefile file with the following content in the same directory as cello.c.
Makefile
```
cello:
	gcc -g -o cello cello.c
clean:
	rm cello
```
Note that the lines under cello: and clean: must begin with a tab space.
To build the software, run the make command:
```
$ make
make: 'cello' is up to date.
```
Since there is already a build available, run the make clean command, and after run the make command again:
```
$ make clean
rm cello

$ make
gcc -g -o cello cello.c
```
Note
Trying to build the program after another build has no effect.
```
$ make
make: 'cello' is up to date.
```
Execute the program:
```
$ ./cello
Hello World
```

You have now compiled a program both manually and using a build tool.