Undefined reference to ´[function]' - c

Question

Edit #1: Please find the solution as an answer to this initial post as a code example is used. Please try also to find a possible solution in What is an undefined reference/unresolved external symbol error and how do I fix it? It didn't help me, but maybe it's suitable for you.
I try to build a project which consists of each two header and application files. If I compile each file, no errors occure. If I build the project, I run into the below error.
cd 'D:\Master\M_32561\9000_A\B13-03'
P:\PortableApps\MinGW\msys\1.0\bin\make.exe -f Makefile CONF=Debug
"/P/PortableApps/MinGW/msys/1.0/bin/make.exe" -f nbproject/Makefile-Debug.mk QMAKE= SUBPROJECTS= .build-conf
make.exe[1]: Entering directory `/d/Master/M_32561/9000_A/B13-03'
"/P/PortableApps/MinGW/msys/1.0/bin/make.exe" -f nbproject/Makefile-Debug.mk dist/Debug/MinGW-Windows/b13-03.exe
make.exe[2]: Entering directory `/d/Master/M_32561/9000_A/B13-03'
mkdir -p dist/Debug/MinGW-Windows
gcc -o dist/Debug/MinGW-Windows/b13-03 build/Debug/MinGW-Windows/B13-03_F1.o build/Debug/MinGW-Windows/B13-03_MAIN.o
build/Debug/MinGW-Windows/B13-03_F1.o: In function `anzeigen_artikelbestand':
D:\Master\M_32561\9000_A\B13-03/B13-03_F1.c:283: undefined reference to `ausgeben_artikelbestand_mit_listenkopf'
build/Debug/MinGW-Windows/B13-03_MAIN.o: In function `main':
D:\Master\M_32561\9000_A\B13-03/B13-03_MAIN.c:39: undefined reference to `erfassen_artikel'
D:\Master\M_32561\9000_A\B13-03/B13-03_MAIN.c:42: undefined reference to `anzeigen_artikel'
D:\Master\M_32561\9000_A\B13-03/B13-03_MAIN.c:45: undefined reference to `aendern_artikel'
D:\Master\M_32561\9000_A\B13-03/B13-03_MAIN.c:48: undefined reference to `loeschen_artikel'
collect2.exe: error: ld returned 1 exit status
make.exe[2]: *** [dist/Debug/MinGW-Windows/b13-03.exe] Error 1
make.exe[2]: Leaving directory `/d/Master/M_32561/9000_A/B13-03'
make.exe[1]: *** [.build-conf] Error 2
make.exe[1]: Leaving directory `/d/Master/M_32561/9000_A/B13-03'
make.exe": *** [.build-impl] Error 2
The project consists of the following files:
B13-03_MAIN.h
B13-03_MAIN.c
B13-03_H1.h
B13-03_F1.c
The undefined functions are declared in B13-03_MAIN.h and defined in B13-03_MAIN.c. Both application files are using B13-03_MAIN.h as a prototype.
Thanks for any help is much aprreciated.

Answer 1

The issue dealt with an incorrect nesting of the undefined functions. I focus on B13-03_MAIN.h and B13-03_MAIN.c.
/* B13-03_MAIN.h */
create_article();
show_article();
edit_article();
delete_article();
Implementation w/ issue:
/* B13-03_MAIN.c */
#include <stdio.h>
#include "B13-03_MAIN.h"
#include "B13-03_H1.h"
void main(void) {
switch(option) {
case abc_c: create_article(); break;
case abc_s: show_article(); break;
case abc_e: edit_article(); break;
case abc_d: delete_article(); break;
default: printf("Undefined option.");
}
void create_article(void) {
...
}
void show_article(void) {
...
}
void edit_article(void) {
...
}
void delete_article(void) {
...
}
} /* This curly braces is incorrectly nested */
Implementation w/o issues:
void main(void) {
switch(option) {
case abc_c: create_article(); break;
case abc_s: show_article(); break;
case abc_e: edit_article(); break;
case abc_d: delete_article(); break;
default: printf("Undefined option.");
}
} /*Incorrectly nested curly brace should be implemented here */
void create_article(void) {
...
}
void show_article(void) {
...
}
void edit_article(void) {
...
}
void delete_article(void) {
...
}