file1: file1.o file2.o
gcc file1.o file2.o -o file1
file1.o: file1.c file1.h
gcc -c file1.c
file2.o: file2.c file2.h
gcc -c file2.c
file1: file1.o file2.o
gcc file1.o file2.o -o file1
file1.o: file1.c file1.h
gcc -c file1.c
file2.o: file2.c file2.h
gcc -c file2.c