Question about makefile
 

I'm learning how to use makefile to maintain a project.
But I encounter a problem.
There are three source files: header.h, appendall.c, appendallmain.c
Below is the makefile:
/*****************************************************/
all: appendall

appendall.o: appendall.c header.h
gcc -c appendall.c

appendallmain.o: appendallmain.c header.h
gcc -c appendallmain.c

appendall: appendall.o appendallmain.o
gcc -o appendall appendall.o appendallmain.o

clean:
rm *.o
/*********************************************************/

what's mean of "all: appendall" at line 1?

Thanks

That just means that the all target depends on the apendall target. In this case, it just means that the all target is synonymous to appendall. Note, however, that the first target in the makefile is the default one (the one used when the user just types make with no argument).