1. Not old. Vintage. :)
Timothy Kline

Z*Magazine: 18-Jun-86 #5

Z*Magazine: 18-Jun-86 #5

  1. Timothy Kline
    Article #11 (214 is last):
    From: xx004@cleveland.Freenet.Edu (Atari SIG)
    Newsgroups: freenet.sci.comp.atari.product.8bit.zmag
    Subject: Z*Magazine: 18-Jun-86 #5
    Reply-To: xx004@cleveland.Freenet.Edu (Atari SIG)
    Date: Sat Jul 3 20:26:27 1993



    _______________________^^^_________
    Zmagazine HOT Atari
    June 18, 1986 News Plus+++
    Ron Kovacs-Editor Vol 1 No. 5
    ___________________________________

    Xx Welcome

    Welcome to another edition of
    Zmagazine. This week we lack a BBS
    Review and the expected interview
    with Scott Brause. As soon as we
    can get the information formatted
    and checked we will publish right
    here!!!!

    Xx In this weeks issue:

    Part 2 of our series on Assembly
    Language programming.

    Family Computing Survey results.

    User Group News

    Zmag BBS Watch

    Atari News, interesting information
    not let out at the CES show.

    and more........

    -----------------------------------
    Xx Zmag Notes
    -----------------------------------
    As I stated in the Special June 15,
    CES issue, I have modified a file
    called Printdoc, made by Jerry
    White. This file allows you to read
    Zmag without pages and also allows
    you to make a hard copy. If you
    are interested in getting this file
    to use or even modify, leave me a
    message on the Syndicate BBS or
    on the BBS you are reading this
    on. The Syndicate number is,
    201-968-8148 300/1200 baud.
    -----------------------------------

    Xx Kieth Does it Again!

    MPP users now can get Express!!

    [76703,4061]
    MPPEXP.DOC 14-Jun-86
    Accesses: 25

    Keywords: MPP EXPRESS TERMINAL
    MODEM DOCUMENTATION

    MPP Express!
    This is the documentation file for
    MPP Express!, available under the
    name of MPPEXP.XMO. Formatted for
    80 columns, just copy it to your
    printer. Capture this file by doing
    a "R"ead command.
    Keith

    [76703,4061]
    MPPEXP.XMO 14-Jun-86
    Accesses: 24

    Keywords: MPP EXPRESS TERMINAL
    MODEM

    MPP Express!
    Here is the MPP version of the
    popular "Express!" terminal
    programs. Created specifically for
    MPP modems, it features such things
    as configurable speed dialing and
    297/300/400/450 baud. Along with
    the highly-dependable XModem
    routines -- your XModem blues are
    over! See MPPEXP.DOC for
    documentation.
    Enjoy!
    Keith Ledbetter
    76703,4061

    These files are available on Compu-
    Serve and also The Syndicate BBS.

    -----------------------------------

    ...................................
    Xx User Group News
    ...................................
    All Interested Parties!!!!!
    MIDI User's Group/BBS
    JOIN DALLAS MIDI USER'S GROUP!!!
    - Free general membership
    - Free computer BBS
    - Free Song File downloads
    - Free Synth patch downloads
    - Free MIDI utility programs
    - Monthly newsletter/meetings
    - All brands of hardware
    /software
    - International Computer Music
    - Database online

    Further info:
    write (by U.S. mail) to:
    Ray Reach
    Dallas MIDI User's Group ("DMUG)
    4306 Pineridge Drive
    Garland, Texas 75042
    PHONE: (214) 272-0963
    -----------------------------------
    fXx Zmag BBS Watch

    Board :ZMAG MESG BASE
    Message # :59
    Date & Time :06/07/86 19:55:03
    Replies :0
    Subject :ZMAG IN JERSEY CONT
    To :RON KOVACS (REC)
    Sent by :CLINTON SMITH

    RON,10 BOARDS! ZMAG MUST BE LIKE
    A RABBIT IN JERSEY.WE ARE COMING
    UP ON 7 BOARDS OUT HERE.I'LL BE
    WAITING FOR THE SB TEXT.GOOD LUCK
    ON SAN FRANCISCO,WHO KNOWS?MAYBE
    WE'VE STARTED A CHAIN REACTION.
    THANKS AND I'LL BE TALKING TO YA.
    L8ER
    CLINTON SMITH
    ZMAG EDITOR
    CHICAGO


    Xx Atari News!!!!
    -----------------------------------
    ATARI PLANNING SUMMER PRODUCTS
    (June 5)

    Atari Corp. is holding some product
    announcements from the CES and
    scheduling them for later in the
    summer. Compatible with the ST
    product line, the new products will
    include a 3.5 floppy with 10MB
    storage capacity, a super-hi-res
    graphics board with 1,000 line
    resolution and a new sound chip.
    Other new products are memory and
    multitasking upgrades as well as a
    new expansion box for holding the
    multiple upgrades.

    ATARI'S 32-BIT MICRO COMING SOON
    (June 6)

    Atari has a 32-bit computer in
    development. The company recently
    signed a Unix licensing agreement
    with AT&T and Atari chairman Jack
    Tramiel has indicated that the new
    machine will run under Unix. When
    the new computer is introduced,
    current ST owners will be offered
    an option to upgrade their machines
    to use the Unix operating system.
    No release date was specified for
    the new computer.

    ATARI TO QUIT TAIWAN PLANT
    (June 4)

    Jack Tramiel is planning to shut
    down Atari's production line in
    Taiwan. In remarks posted on a
    bulletin board service after he met
    with Atari owners in Massachusetts,
    the Atari chairman said that under
    the right conditions computers
    could be constructed in the US with
    the same cost efficiency as in
    Taiwan. Tramiel set no deadline for
    the manufacturing changeover but he
    did indicate the move was not in
    the immediate future.

    Reported By:--James Moran


    AMIGA DEVELOPERS UNHAPPY
    (June 3)

    Third-party software developers
    are voicing their concern over what
    they perceive is a lack of support
    and concern by Commodore Business
    Machines. Many developers have
    dropped plans to continue Amiga
    development until they receive some
    assurances that Commodore will
    supply necessary development
    information. Commodore is trying to
    assure developers and the Amiga
    dealer network, that support will
    continue regardless of internal
    restructuring. Last week, Randy
    Weiner of Amiga Technical Support
    told developers they "will continue
    to receive the full support of
    Commodore. We are not about to
    'dump' on anyone. I, for one,
    understand the importance of such
    support, and what it means to the
    future of the Amiga, and Commodore
    itself."

    Reported By:--James Moran

    -----------------------------------

    -----------------------------------
    Xx Family Computing Survey

    WHAT COMPUTER OWNERS THINK ABOUT
    MAIL ORDER

    The vast majority of computer
    owners have bought by mail or are
    willing to do so, according to
    FAMILY COMPUTING's April survey on
    Mail Order Buying. Over a three-
    week period, 238 people completed
    the survey. Here are the
    highlights:

    1) Only 7% said they would never
    purchase computer equipment by mail
    72% said they have bought by mail.

    Of those buyers, 55% were "very
    satisfied," and 25% were "somewhat
    satisfied" with the service.
    Only 3% were "not satisfied."

    Product orders broke down like this

    Software (72%)
    Peripherals (50%)
    accessories (36%)
    Computers (10%).

    The single most important reason
    people gave for mail- order buying
    was "lower prices," noted by 50% of
    respondents. The single most
    important (67%) drawback was "you
    can't see or try out what you're
    buying." The relative index of
    buyers by machine broke down like
    this:

    Tandy/Radio Shack (90%)
    ADAM (85%)
    Atari (73%)
    Commodore (71%)
    IBM (71%)
    Apple (68%)

    These results are published in the
    August issue of Family Computing,
    with a cover story on MAIL ORDER
    BUYING.
    -----------------------------------
    -----------------------------------
    Xx Assembly Language
    -----------------------------------
    ANTIC ONLINE
    ANTIC PUBLISHING INC., COPYRIGHT
    1985. REPRINTED BY PERMISSION.
    -----------------------------------
    ASSEMBLY LANGUAGE - LESSON 2

    ** 6502 ARITHMETIC **
    By: CHRIS CRAWFORD

    NUMBER SYSTEMS

    In this lecture I will take up
    the problem of arithmetic on the
    6502. I choose this topic only
    because it is fairly simple to do
    on the 6502. There are a couple of
    nerve-jangling problems associated
    with 6502 arithmetic, but I will
    breeze over those in a very
    cavalier fashion.

    Before we can do arithmetic,
    though, you must know a little bit
    about number systems. There are
    three that you must know: decimal,
    binary, and hexadecimal.

    Decimal is the standard numbeat
    you have used since grade school.
    You count 0, 1, 2, 3, 4, 5, 6, 7,
    8, 9, and then you reach 0 again,
    so you put down a 1 in the tens
    place and resume counting from 0.

    Binary works the same way,
    except that there are only two
    digits, not ten. The two digits
    are 0 and 1. You count 0, then 1,
    then you reach 0 again, so you put
    down a 1 in the twos place and
    resume counting from 0. Thus,
    counting from 0 to ten in binary
    like this:

    Decimal Binary
    0 0
    1 1
    2 10
    3 11
    4 100
    5 101
    6 110
    7 111
    8 1000
    9 1001
    10 1010

    In binary, instead of having
    ones, tens, and hundreds places, we
    have ones, twos, fours and eights
    places. It takes a lot more digits
    to express a number in binary, but
    then again, we have only the two
    numberals 0 and 1 to work with, so
    what does one expect?

    The hexadecimal number system is
    a base-16 system. In this system,
    you count from 0 to 16 like so
    0,1,2,3,4,5,6,7,8,9,A,B,C,D,E ,F,
    10. The 10 in hexadecimal really
    means 16 in decimal. So 10 is 16,
    right? Black is white, truth is
    likes....stay with assembly
    language long enough and you'll
    believe anything.

    Actually, it's easy to avoid
    confusion. We use little prefixes
    to tell you and the computer
    whether a number is expressed in
    decimal, binary, or hexadecimal.
    No prefix means decimal. A $
    prefix means hexadecimal; a % means
    binary. Thus %10 means 2 while $10
    means 16, but 10 means just plain
    old 10. Hexadecimal is not hard to
    learn at all; if you go into any
    store you will see that they use
    hexadecimal on all their signs.

    ADDITION AND SUBTRACTION

    Addition with the 6502 is very
    simple; it uses the ADC
    instruction. This instruction
    means "Add with Carry"; I'll get to
    the Carry part in just a moment.For
    now,let me explain the instruction.
    The ADC instruction has an operand,
    normally a location in memory. When
    the instruction is executed, it
    takes the contents of that memory
    location and adds that value to the
    value in the accumulator.

    It leaves the sum of the two
    numbers in the accumulator. This
    of course destorys the old value in
    the acucmulator. You can use the
    immediate mode of addressing with
    the ADC instruction, in which case
    it adds the value itself. Thus,
    "ADC # 9" will add a 9 to the
    contents of the accumulator, while
    "ADC FISH" will add the contents
    of address FISH to the accumulator.

    Subtraction is just like
    addition. The instruction to use
    is SBC, which means "Subtract
    Borrowing Carry". Again, I'll tell
    you about the Carry part in a
    moment. This instruction subtracts
    the operand from the contents of
    the accumulator, leaving the result
    in the accumulator, It also can be
    done in either immediate mode (e.g.
    SBC#5) or absolute mode (e.g., SBC
    GOAT).

    WORD LENGTH PROBLEMS

    If that were all there were to
    arithmetic with the 6502,
    programmers would be paid a lot
    less. The first killer problem is
    that the 6502 uses 8-bit words;
    that is, the numbers that the 6502
    stores and works with are only 8
    bits wide. This means that the
    biggest number the 6502 can
    comprehend is 255. Uh-oh! What
    happens if you want to have a
    checkbook balancing program and you
    have more than $255? What happens
    if you get more than 255 points in
    your "Decapitate the Orphans" game?
    In fact, what happens if you just
    ignore the limit and add, say, 10
    to 250?

    Well, believe it or not,the 6502
    will give you an answer of 4. Why?
    The number system that the 6502
    uses is like a wheel, with 0 at the
    top, counting clockwise 1,2,3,...
    all the way up to 255, which lies
    right next to the 0. If you go up
    from 255 you just wrap around past
    the 0 and start all over. Similarly
    if you subtract 2 from 0, you'll
    get 254.

    The solution to all this is
    provided by the Carry bit,
    discussion of which I've been
    putting off unitl now. The
    Carry bit is a flag that the 6502
    uses to remember when it has done
    arithmetic that carried it over the
    boundary between 0 and 255. By
    using it properly, you can solve
    your arithmetic problems.

    The first trick to using the
    Carry bit is to use multi-byte
    words. This means that, instead of
    using a single byte to store a
    number, you use several. For
    example, if you use two bytes to
    remember a number, you can store a
    number as large as 65,535. three
    bytes lets you to to 16,777,215.
    Four bytes lets you go to 4,294,
    967,295. big enough for you?

    To use multi-byte arithmetic,
    you set up a series of additions of
    subtractions. Suppose, for example,
    that you want to add two two-byte
    words. The program fragment to do
    this would look like this:

    LDA LOFISH
    CLC
    ADC LOGOAT
    STA LOANSR
    LDA HIFISH
    ADC HIGOAT
    STA HIANSR

    This little fragment of code
    assumes that the first two-byte
    value is called (LOGOAT, HIGOAT),
    and that the , HIANSR). The new
    instruction, CLC, stands for "Clear
    Carry" and it means that the Carry
    bit should be set to 0. It should
    always be used with all additions
    except chained additions like this
    one.

    The code does the following:
    first it adds the two low values.
    If the addition resulted in a wrap-
    around (result greater than 255),
    then the Carry bit was set;
    otherwise, it was cleared. Then it
    performed the second addition,
    adding in the value of the Carry
    bit (That's why we call it "Add
    with Carry"). Thus, if a wrap-
    around occurred, an additional one
    was added into the high sum. This
    system insures that multi-byte
    addition works properly.

    For subtraction, you use the SEC
    instruction ("Set Carry").
    Otherwise, you handle subtraction
    the same way that you handle
    addition. In both addition and
    subraction, though, the low bytes
    must be handled first, then the
    higher bytes in the proper order
    (lower to higher).

    DECIMAL & SIGNED ARITHMETIC

    There are two variations on
    standard 6502 arithmetic. Both are
    so rarely used that I will not
    treat them here. The first is
    decimal arithmetic using the
    Decimal flag. This allows you to
    set up an automatic decimal adjust
    mode. This is useful in certain
    types of arithmetic, decimal adjust
    mode. This is useful in certain
    types of arithmetic, primarily BCD
    arithmetic.

    If you don't know what this is,
    don't bother with the Decimal flag.
    Your program should always begin
    with the instruction CLD, which
    means "Clear Decimal Flag". I will
    tell you this just once: failure to
    clear the decimal flag is the
    source of the most frustrating and
    impossible-to-trace bug in the
    6502. Every single program should
    start with the instruction CLD.

    The second arcane bit of 6502
    arithmetic is signed arithemetic.
    It uses the V flag ("oVerflow").
    Signed arithmetic is always
    confusing and seldom useful. In 7
    years of working with the 6502, I
    have never had need of it. Don't
    bother.

    LIMITATIONS ON 6502 ARITHEMETIC

    There are quite a few
    limitations on 6502 arithmetic.
    There is no facility for
    multiplication and division; you
    have to wirte subroutines to do
    that. You must design your programs
    to make do with 8-bit words;
    failing in that, you must use
    multi-byte arithemetic, with its
    consequent price in speed and TAM.
    All in all, arithmetic is a real
    pain on the 6502. This is the major
    reason why most 6502 programs do so
    little arithmetic.

    -----------------------------------
    Next week part three of this 8 part
    series on Assembly Language.
    -----------------------------------
    Xx Atomic Network News
    ********** ANNOUNCEMENT ***********
    FROM THE ATOMIC NETWORK
    WE ARE HAVING A CONTEST
    THE PERSON WHO COMES UP WITH THE
    BEST IDEA FOR A LOGO FOR THE ATOMIC
    NETWORK WILL WIN..............
    A $200.00 GIFT CERTIFICATE
    AT
    J&R MUSIC WORLD
    THE STARTING DATE: APRIL 2,1986
    THE ENDING DATE : AUGUST 21,1986

    * CONTEST RULES *

    ALL ENTRIES MUST BE POSTMARKED NOT
    EARLIER THEN APRIL 2,1986 OR AFTER
    AUGUST 21,1986

    ALL ENTRIES MUST CONTAIN:
    1...HANDLE(IF ANY)
    2...REAL NAME.
    3...ADDRESS.
    4...PHONE NUMBER(VOICE LINE)
    5...A BBS NAME AND NUMBER WHERE YOU
    CAN BE REACHED.

    ALL SYSOPS AND CO-SYSOPS OF THE
    ATOMIC NETWORK ARE NOT ELIGABLE

    SEND ALL ENTRIES TO:

    THE ATOMIC NETWORK
    P.O. BOX 594
    KNICKERBOCKER STATION
    N.Y. N.Y. 10002

    -===================-

    Xx Next Atomic Meeting

    The next Atomic Network meeting
    will be held on Sunday June 22,
    at 1pm. Anyone interested in
    details, please call the Valhalla
    BBS @ 212-598-0243

    -===================-


    ___________________________________
    Zmagazine #5 June 18, 1986
    Next edition June 25, 1986
    Please contribute!! Take care!
    ___________________________________