Notes for 09/16 CISC105 Fall 2005

(1) We talked about the Makefile for lab02
and mentioned that you can edit it to change
between using gcc and cc, if your account is
still having problems with gcc.

If you are still having problems with gcc,
see Prof. Conrad for help; he has some new
information on how to fix that.

(2) Machine language... 

a.out is in machine language

machine language is "binary codes" that
correspond to instructions like "add",
"multiply", "compare".

The compiler (cc or gcc) converts from
C into machine langauge.

You can also specify a different file name
for the machine language by writing:

cc -o fred lab01a.c

In that case, instead of putting the machine
langauge (the binary) into a.out, it gets
put into a file named "fred".

To run it you would type:

./fred


But fred is a silly name... instead, if the
file is foo.c, we usually name the binary foo.

If the file is bar.c, we would name the binary
exectuable file: bar

If you type "make fum", the system looks
for a file fum.c   If one exists, it will
compile with the command:

cc -o fum fum.c

You can also write  a "Makefile" that specifies
rules for what happens when you just type
"make".

Typically, with a Makefile, if you type

make clean

then the binaries get deleted to save space.
You can always bring them back later by typing
"make" again.

If you type make more than once, the second
time it has no effect, unless the .c files
have been changed since the last time you
typed make.

YOu can read more about "make" and "Makefiles"
in one of the appendices of your Andersen text.

Now: seg faults...

if you have a mismatch between the type of a variable
and the format specifier... 

you can get a segmentation fault


Three files are in the directory that show
three different conditions that can cause
segmentation faults.

Take a look at them.

******************