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:sectnums:
== Application Program Compilation

This guide shows how to compile an example C-code application into a NEORV32 executable that
can be uploaded via the bootloader or the on-chip debugger.

[IMPORTANT]
If your FPGA board does not provide such an interface - don't worry!
Section <<_installing_an_executable_directly_into_memory>> shows how to
run custom programs on your FPGA setup without having a UART.

[start=1]
. Open a terminal console and navigate to one of the project's example programs. For instance, navigate to the
simple `sw/example_blink_led` example program. This program uses the NEORV32 GPIO module to display
an 8-bit counter on the lowest eight bit of the `gpio_o` output port.
. To compile the project and generate an executable simply execute:

[source,bash]
----
neorv32/sw/example/blink_led$ make clean_all exe
----

[start=3]
. We are using the `clean_all` target to make sure everything is re-build.
. This will compile and link the application sources together with all the included libraries. At the end,
your application is transformed into an ELF file (`main.elf`). The _NEORV32 image generator_ (in `sw/image_gen`)
takes this file and creates a final executable. The makefile will show the resulting memory utilization and
the executable size:

[source,bash]
----
neorv32/sw/example/blink_led$ make clean_all exe
Memory utilization:
   text    data     bss     dec     hex filename
   3176       0     120    3296     ce0 main.elf
Compiling ../../../sw/image_gen/image_gen
Executable (neorv32_exe.bin) size in bytes:
3188
----

[NOTE]
Make sure the size of the `text` segment (3176 bytes here) does not overflow the size of the processor's
IMEM (if used at all) - otherwise there will be an error during synthesis or during bootloader upload.

[start=5]
. That's it. The `exe` target has created the actual executable `neorv32_exe.bin` in the current folder
that is ready to be uploaded to the processor.

[TIP]
The compilation process will also create a `main.asm` assembly listing file in the current folder, which
shows the actual assembly code of the application.