Fish 'n' More 2/fishmore-publicdomainlibraryvol.ii1991xetec.iso/fish/languages/northc_384/hello/hello.doc

Text File | 1990-09-08 | 12KB | 325 lines

  (c) 1990 S.Hawtin.
  Permission is granted to copy this file provided that:
   1) It is not used for commercial gain
   2) This notice is included in all copies
   3) Altered copies are marked as such.

  No liability is accepted for the contents of the file.

  This file outlines the steps you should take to create a simple 'C'
program, compile it and run it.  This should work on anything from an
unexpanded Amiga 500 upwards, however if you have an unexpanded Amiga 500
go out and buy a second drive, they don't cost much and they make your
life so much easier.

  So, you have just got this new disk from the public domain, and you are
wondering how to become a top 'C' wizard in an afternoon.  Well you must
start by writing a program.  Lisp programmers always write factorial as
their first program, but that is because they are strange.  'C' being a
"real" language all 'C' programmers start with the "Hello World" program.

  This set of instructions assumes that the NorthC system is on a floppy
called "NorthC:", if you are running on a hard disk, or a floppy called
something else, you must make sure that the "NorthC:" device is set up by
the script file "setup-NorthC".

  The steps you should take to produce your first program are as follows.

1) Backup Your Disk

  Once you have unpacked your NorthC disks you should make copies of each
of them.  None of the programs should need to write to the "NorthC:" disk
so you should write protect that, move the little tab so that you can see
through the hole.  Either use the "Workbench"-"Duplicate" option, or
better the CLI command "diskcopy" to make a copy of the NorthC floppy.
Once you have done this always use the copy, that way if something goes
wrong you still have the original.

2) Start the CLI

  As it currently stands you must run the 'C' compiler from the CLI, you
must start up a CLI shell.

3) Set up the NorthC environment

  You will need to do this every time you run the 'C' compiler, once you
get bored enough you could put this in the "s:startup-sequence" file.

  How you set up the environment depends on your configuration, there are
three possibilities, either you have a hard disk, you have a second
floppy,or you only have a single floppy.

  Edit the file "Setup-NorthC" on the "NorthC:" disk, run "memacs" from
the "Extras 1.3" disk, select "Project"-"Visit File" then type
"NorthC:Setup-NorthC".  At the end of the file are three "execute"
commands, comment out the two that do not apply, so if you are running on
a single drive Amiga the end of the file should be

    execute NorthC:Single-make
    ;execute NorthC:Dual-disk
    ;execute NorthC:Hard-disk

with a ';' in front of the two lines that do not apply.  Then save the
"setup-NorthC" file back on the "NorthC" disk.

3a) A Single Floppy

  Type the CLI command

    execute NorthC:Setup-NorthC

this will copy the necessary programs into the ram disk.  Once you have
compiled your first program I would suggest you use a slightly more
complex way to run the system, see 8a below.

3b) If you have a second floppy drive

  Place the NorthC floppy into the second floppy drive, that is "df1:",
and type

    cd NorthC:
    execute setup-NorthC

this will add the "bin" directory to the search path and tell the system
where to find the 'C' libraries.

3c) If you have a hard drive

  To run NorthC on a hard drive you need to copy the executables, the
include files and the libraries on to your hard drive.  Place the
"NorthC:" disk into the floppy and type

    cd NorthC:
    execute setup-NorthC

this will copy the executables to the "c:" directory, and create two new
directories on "hd0:", if these directories are not suitable for your
setup edit the "NorthC:Hard-Disk" file before running "Setup-NorthC".

  Once the files have been copied comment out all the "Hard-Disk" file
except the final line.

4) Change Directory to the source directory

  The command

    cd "NorthC Examples:hello"

should move you to a suitable directory, this is where you will create the
"Hello World" program.

5) Create a source file

  You should use "memacs" from the 1.3 Extras disk to enter a 'C'
program,the command

    "Extras 1.3:tools/memacs" hello.c

will start the editor up, enter the following file

    #include <stdio.h>

    main()
       {/* The simplest 'C' program ever */
        printf("\a\aHello World\n");
        }

once you have typed this in select "save-exit" on the "Project" menu, this
will save the file to the disk and exit the program.

  You should learn to use "memacs" when typing 'C' programs, it is a
version of the most widely used program editor for 'C' programmers.  It
has a large number of features that make it very powerful for editing programs.

6) Compile the file

  If you are running with a single floppy you will not be able to use the
"cc" command, you will have to jump strait to step (8).  Assuming you have
a second drive and you called your file "hello.c" type the command

    cc hello.c

after much clunking of disk drives, you will find that your directory
contains a file "a.out" as well as "hello.c".  Use the command

    list

to show you the contents of the directory.

7) Run the file

  Once "a.out" has been created you can run the program by typing

    a.out

you will be amazed by the result, or there again you might not be.  Once
you are bored with "a.out" remove it from the directory with the command

    delete #?.out

8) Create a Makefile

  "Real" 'C' programmers rarely us the "cc" command directly, they
normally use a program called "make".  This file will be different if you
only have one disk drive.

8a) If you only have one disk

  If you only have a single floppy system you will need to create a file
called "Makefile" the complete file should read

    hello : hello.o
         NorthC:bin/blink with $*.blink

    .c.o:
         NorthC:bin/NorthC $*.c
         NorthC:bin/A68K -q -g $*.s
         delete $*.s

    .asm.o:
         NorthC:bin/A68K $*.asm

    .s.o:
         NorthC:bin/A68K $*.s

you will need to add the extra items such as ".c.o", ".asm.o" and ".s.o"
to all your makefiles until you get a second drive.

8b) If you have a second drive

  Use "memacs" to create a file called "Makefile" containing

    hello : hello.o
            blink with $*.blink

this tells "make" how to build the "hello" program.

9) For all machines

  Once you have created the "Makefile" we must create a ".blink" file for
the linker, use the command

    NorthC:bin/make $*.blink

this will create a file called "hello.blink", now type the command

    NorthC:bin/make

the machine will now translate your 'C' code into a program.  Use the
"list" command to look at the directory, it should now contain "hello.o"
and "hello".  Try the command

    hello

for some astounding results.  The file "hello.o" is an "object" file, I
will explain what they are for later.  The "hello" directory also contains
a "hello.info" icon file, once you have created your "hello" program you
can run it by double-clicking the "hello" icon in the directory.

  It is good practice to always use the "make" program when compiling your
'C' programs, if you want to know why read "make.doc".

10) Go again

  Edit the "hello.c" file to do something else, get ideas from published
'C' programs, public domain programs, friends, and anywhere else you can.

  There are a number of example programs on this disk, also look on the
"NorthC" disk in the "tools" directory, steal all the good ideas from them
(if you can find any).

11) Get serious

  Buy yourself a copy of "Kernigan & Ritchie" or better yet get someone
else to buy one for you.  I know it is expensive but if you get seriously
into 'C' you will get your own copy in the end anyway.  It really is the
best book on 'C' ever written, even if the code layout is a bit weird.

  Find a good book for AmigaDOS, I cannot recommend any book here as I
have yet to find one that doesn't require a degree in computer science to
understand, however I am sure that some easy to understand books are around.

  Read the "libc.doc" file on this disk to see what is currently
implemented in the NorthC library, read the "Bugs.doc" file especially if
a program does something you really didn't expect, or if it fails to compile.

12) Multiple files

  As a taster for the complexities of programming I will explain about
compiling large programs that are split over many files, ignore this bit
if you want.

  Once you have a decent sized program you will want to split it over many
source files, suppose you have a program that is written in the files
"foo.c" "bar.c" and "baz.asm".  You can compile the files with the command

    cc -ofoo foo.c bar.c baz.asm

however this will recompile all three files each time you compile the program.

  The 'C' world contains four different types of file, source files,
assembler files, object files and executable files.  You can usually tell
which category any file comes in by its extension, for example source file
names end in ".c", for example "foo.c" "this.is.source.c" and so on.
Object files normally end in ".o", assembler files end in ".s" or ".asm",
and executable files have no extensions.

  The 'C' compilation process contains three stages, first a compiler that
translates source files into assembler files, then an assembler that
translates assembler files into object files, and finally a linker that
combines a number of object files to create an executable.  The "make" and
"cc" commands will call each of these stages for you, when you type

    cc -ohello hello.c

"cc" will first call the compiler, called "NorthC", to create a file
"hello.s", next "cc" will call the assembler, called "A68K", to create a
file "hello.o", and finally it will call the linker, "Blink", to make the
executable "hello", once this is created it will delete the intermediate
files "hello.s" and "hello.o".

  The "make" command tends to leave the object files in the directory.  So
when we make the program the files "foo.o" "bar.o" and "baz.o" stay
around.  Now if the user changes "baz.asm" make knows that it must
reassemble "baz.asm" then link "foo.o" "bar.o" and "baz.o".  It knows that
it does not need to recompile "foo.c" and "bar.c".

  Once you have understood all that you should find a good 'C' book and
lookup libraries, not to be confused with Amiga libraries, this will get
you nicely confused again.  I hope that didn't confuse you.

  Examine the source code for "cc" in tools, this will show what "cc" can
do, if you would rather that it did something differently change the file
"cc.c" make a note of the fact you have changed it at the top of the file
and recompile it.  The original "cc.c" was hacked together in a single
evening with just the UNIX "cc" manual for a spec, so I won't mind if you
'improve' it, provided you note what changes you have made at the top of
the source.  If you manage to create a better version please send it to
me, tell me if I can use it in future versions of NorthC.

13) Share and Enjoy (or Go Stick Your Head in a Pig)

  Once you understand 'C' you should share your knowledge, if you have an
interesting program put it into the public domain or make it shareware, if
you find learners in 'C' and AmigaDOS explain how to do things, always
remember that you once knew nothing about computers, even if it was a long
time ago.  Most of all you should have fun with computers, unless of
course you are a COBOL programmer.

14) After

  If, as the sun slowly sets, you realise that the astounding NorthC disk
has turned you from a puny BASIC programmer into a towering 'C' wizard you
should now get a "scheme" interpreter, for example from Fish 149, and a
copy of "The Structure and Interpretation of Computer Programs" by
"Ableson & Sussman".  This book is the best introduction to programming I
have ever read, once you have completed it you will know more about
programming than most professionals.

By the way the factorial function in scheme is

    (define (factorial n)
        (if (= n 0) 1
            (* n (factorial (- n 1)))))