Create and build a "Hello world" application

Follow these steps to create and build a "Hello world" application:

Create a directory called hello_world:
```
$ mkdir hello_world
```
Inside the hello_world directory, create a file named hello-world.c:
```
$ cd hello_world
$ touch hello-world.c
```

Edit the hello-world.c file with the following contents:

hello-world.c

#include <stdio.h>
#include <unistd.h>

int main(int argc, char *argv[]){
	int i;

	for (i = 1; i <= 10; i++) {
		printf("%d - Hello world!\n", i);
		sleep(1);
	}

	return 0;
}

Create a makefile file inside the hello_world directory:
```
$ touch Makefile
```

Edit the file Makefile with the following contents:

Makefile

BINARY := hello-world
CFLAGS += -Wall -O0

.PHONY: all
all: $(BINARY)

$(BINARY): hello-world.o

.PHONY: clean
clean:
	-rm -f *.o $(BINARY)

Before building the code, export the toolchain environment:

$ . /opt/dey/4.0-r7/ccmp15-dvk/environment-setup-cortexa7t2hf-neon-vfpv4-dey-linux-gnueabi

Cross-compile the code using make.

$ make

If you are building a Qt application, run qmake before cross-compiling:

$ qmake

The binary file, hello-world, is generated inside the directory hello_world.

$ ls -l
total 28
-rwxrwxr-x 1 user user 12084 dic 18 12:39 hello-world
-rw-rw-r-- 1 user user   199 dic 18 12:39 hello-world.c
-rw-rw-r-- 1 user user  4968 dic 18 12:39 hello-world.o
-rw-rw-r-- 1 user user   189 dic 18 12:39 Makefile