Millennium Time Capsule/AC2000.BIN/disks/ac10disk/atozbook/o.txt

Text File | 1998-06-10 | 16KB | 484 lines

                             "The Atari A to Z"
                              by Mark S Baines
                      Copyright (c) 1998 Mark S Baines
                             All Rights Reserved


       YOU MUST READ "READ_ME.NOW" BEFORE YOU LOOK AT ANY OF THIS FILE
*****************************************************************************


O


Obey
To perform the operations of an instruction.


Object
An entity. Also, the screen graphic shapes in a WIMP/GUI system, such as
icons, menus, boxes.


Object code
Also machine code. The final result of a language translation.


Object library
A library of object code modules that can be called or included in programs at
compilation and link time.


Object oriented graphic
See Vector graphic, Drawing program, GEM metafile.


Object orientated programming - OOP
A method of programming where the emphasis is on objects, such as data
structures, and the operations performed upon them as opposed to control
orientated programming where emphasis is on working out the program's flow of
control. OOP is well suited to writing GUI programs where dialog boxes and
sets of icons together with the routines connected with them can be treated as
objects in the program. As modular or structured programming was the trend of
the 1980s, OOPs is the fashion of the 1990s. The C++ language offers
facilities to assist OOP although it is not a fully-fledged OOP language, such
as Smalltalk.


OCR
Optical Character Recognition. Computer input equipment and techniques for
identifying printed or handwritten characters by photoelectric sensing and
analysis of their patterns.


Octal
A numeration system with a radix or base of eight using digits 0-7. The first
five digit positions have the weights 1, 8, 64, 512, 4,096. In octal, decimal
10 would be 12.


ODA
Open Documents Architecture. A standard defined by the ISO and CCITT which
allows documents containing graphics, text, spreadsheet data etc. to be passed
between computers of different makes.


Odd parity
See Parity.


OEM
Original Equipment Manufacturer. A term applied by a supplier or distributor
for a manufacturer who provides the components used in their product. Most (if
not all) machines consist of components made by various OEMs and put together
by the supplier whose name appears on the device. No components in an Atari
computer are actually manufactured by Atari.


Off-bit
A term applied to a 0-bit as an indicator or flag.


Off-hook
The status of telephone equipment in which dialling is performed and messages
are transmitted and received.


Off-line
Peripheral devices that are not under the control of a computer by being
switched off or by the communications link being broken. Also, the state of
not being connected to a remote data network.


Off-line reader
A program into which packets of messages and mail are loaded which enables the
user to read them and reply to them as if on-line to a telecommunications
network. The off-line reader will also prepare a message packet to up-load to
the network containing the user's replies and messages. Off-line readers save
enormous amounts of time on-line and thus expense.


Off-line storage
Any storage medium that has to be loaded or connected to the computer when
required, such as a tape backup device.


Offset
A displacement, a difference between a location and a reference location, for
instance, a relative address is an 'offset' of a base address. Also, to
compensate or balance.


Offspring
Synonymous with member.


OK button
Common WIMP/GUI alert or dialog box button confirming the action to be taken
and usually the default. According to Atari, "OK" should be in upper case and
the button to the left of the "Cancel" button.


OLR
Off-Line Reader.


OMR
Optical Mark Recognition. Computer input equipment for identifying and
interpreting marks (short lines, filled-in squares) on documents by means of
changes in reflected or transmitted light. Commonly used on multiple choice
exam papers and on National Lottery cards.


On-bit
A term applied to a 1-bit as an indicator or flag.


On-board
On the same printed circuit board as other components.


On-chip
On the same integrated circuit as other elements, such as the on-chip RAM
cache of a MC68030 CPU.


On-demand
When required or requested.


On-hook
The status of telephone equipment in which it is ready to receive an incoming
call.


On-line
The state of peripheral equipment connected and ready to perform its function
being accessible to a computer. Also, having a terminal or computer connected
to a remote interactive data processing service, data network or information
system and receiving data from them.


On-line storage
Storage directly accessible to a computer at any time, such as RAM and disk
drives.


One-bit
A 1-bit, a binary digit and the basic unit of storage and transmission.


One-way communications
Communication in one prearranged direction only, a simplex system.


OOP
Object Orientated Programming.


Opcode
OPeration CODE. That part of an object code instruction that consists of the
operator. Also, an instruction set.


Open
An operating system function that locates and identifies a file in storage and
its access permission. Also, to stop the flow of electricity in a circuit.


Open circuit
An electrical circuit where the current has been removed.


Operand
A value that is used or manipulated during the execution of an instruction,
the basic unit of data. In the expression x + 3, both x and 3 are operands.


Operating system - OS
A set of tested, interrelated programs to exercise management and control
functions over processing. It provides storage and processing management,
protection of code and data including its validation, backup and error
control, a human interface and in multi-user systems logging and accounting
functions. The standard microcomputer operating system is MS-DOS and that in
the ST-Falcon range is TOS with the addition of MultiTOS.


Operating system header block
All versions of TOS have a set of data at the start of the code which provides
various information as to its identity and other miscellaneous details. The
system variable _sysbase at address $4F2 points to the location of this header
block and must be used by programmers, who should not assume that the system
header block is in the ROM or at addresses $00FC0000 or $00E00000.

The structure of the header block is:

  typedef struct _osheader
  {
    unsigned short os_entry;    /* offset $00 */
    unsigned short os_version;  /* offset $02 */
    void (*reseth)(void);       /* offset $04 */
    struct _osheader *os_beg;   /* offset $08 */
    void *os_end;               /* offset $0C */
    void *os_rsv1;              /* offset $10 */
    long *os_magic;             /* offset $14 */
    long os_date;               /* offset $18 */
    unsigned short os_conf;     /* offset $1C */
    unsigned short os_dosdate;  /* offset $1E */
    /* The following fields are not available in TOS 1.0 */
    void **p_root;              /* offset $20 */
    unsigned char *pkbshift;    /* offset $24 */
    BASEPAGE **p_run;           /* offset $28 */
    void *p_rsv2;               /* offset $2C */
  } OSHEADER;

  Table O1: Interpretation of Operating System Header Block

  Offset from   Meaning                                  TOS 1.4 value
  _sysbase
  $00           Entry, BRA to reset handler              $    602E
  $02           Major TOS version number                 $      01
  $03           Minor TOS version number                 $      04
  $04           Address of routine executed upon reset   $00FC0030
  $08           Start of operating system                $00FC0000
  $0C           Start of free RAM (end of system RAM)    $0000611C
  $10           Address of default shell                 $00FC0030
  $14           Address of GEM MUPB                      $00FE81FE
  $18           ROM creation date in hex $MMDDYYYY       $04061989
  $1C           OS configuration bits                    $    0007
  $1E           ROM creation date in GEMDOS format       $    1286
  The following fields are not available in TOS 1.0
  $20           Pointer to _root system variable         $0000378C
  $24           Pointer to kbshift system variable       $00000E7D
  $28           Pointer to _run system variable          $00005622
  $2C           unused, reserved                         $00000000

The OS configuration bits field consists of the country code and video sync
mode that the TOS was compiled for. Bit zero is 0 to indicate NTSC mode or 1
to indicate PAL mode. The remaining bits give the country code after being
shifted right by one bit. Thus the above value of $07 gives %111 binary which
is %1 for PAL mode and %11 or three for Great Britain (see Country).

The three system variables are only available in TOS 1.2 and later. _root
contains the address of the GEMDOS memory pool structure. kbshift contains the
address of the system keyboard shift state variable which provides a quicker
way of reading the state of the keyboard shift state than using the Kbshift()
function. The _run variable contains the address of the basepage of the
currently executing GEMDOS process.


Operating system nucleus
See Kernel.


Operation
During execution, that which is performed on or with data.


Operator
That part of an instruction or expression that specifies the operation to be
performed on or with the operand(s), such as 'add', 'less-than' or 'NOT'. It
can also be the symbol indicating that operation, such as +, < or NOT. Also, a
person who performs processing related tasks in a mainframe/minicomputer
computer installation.


Optical
A term denoting sensing and input by photoelectrical means.


Optical character reader
A device that carries out optical character recognition.


Optical coupler
Also optocoupler and opto-isolator. A sealed device containing an infra-red-
emitting photodiode and a phototransistor sitting in a circuit and
electrically isolating the circuit on either side of the component and so
preventing noise and peak pulses from passing to the output side. The ST-
Falcon range has these fitted to the MIDI lines for safety preventing
excessive current from passing into the computer.


Optical disk
A storage device using laser beams to write (sometimes once only) and read
data from a disk. The data is more secure than magnetizable disks and optical
disks have far greater capacity.


Optical mark reader
A device that carries out optical mark recognition.


Optical type font
A special set of characters designed for machine reading.


Optimization
Also, tuning. The enhancement of a system or program to improve its speed of
operation and/or storage space. This is often a process in programming where
such methods can be done manually on the source code or by certain optimizer
programs on the object code.


Options menu
A typical GEM application menu which contains such items as "Document
defaults..." and "Preferences...".


Optofile
Atari name for the abortive CDAR504 CD-ROM drive.


OR
A logic operation with an output that is 'true' if any input is true and
'false' if all inputs are false.


Order
The operation of manipulating the physical relationship of items in a group
according to some rule. Also, a command. Also, a term used to indicate that a
value is an approximation, as in "in the order of 10%".


Order code
An instruction set.


Origin
A base address. Also, a root of a tree data structure.


Originate
To initiate or to be the source of.


Originate mode
A mode of telephone equipment (such as a modem) in which it is dialling a data
station in order to set up a transfer.


Orthogonal
Having the characteristics of a matrix with items that are accessible at the
intersections of two or three coordinates.


OS
Operating System.


Oscillate
To vibrate, to make a repetitive change of state or value.


Oscillator
A device that generates high-frequency pulses for purposes of synchronization
and event timing. Most are crystal oscillators that take advantage of the
inherent resonance of a quartz crystal to obtain frequency stability. The ST's
32 MHz oscillator provides the master clock frequency for the whole computer
which is cut down to lower frequencies by the MMU, SHIFTER and GLUE chips for
use by them and other integrated circuits including the CPU.


OSI
Open Systems Interconnect. An ISO international standard of protocols to
eventually replace the Internet TCP/IP protocols. See TCP/IP.


OTPEPROM
One Time Programmable Erasable Read-Only Memory. An EPROM which can only be
programmed once as the data on it cannot be erased.


Outline
The effect of drawing a line around a WIMP/GUI object for emphasis. Also, the
main structure of an article, book, report etc. consisting of titles, headings
and notes.


Outline font
See Scalable font.


Outliner
A text editor program helping to produce outlines of textual material to be
written in a word processor. Outliners usually allow text to be 'folded', that
is, some parts to be hidden so that the overall structure is more easily seen.


Output
To produce as a result of processing. That which is produced by a process or
device. Also, a transfer to a peripheral device.


Output buffer
In a communications interface, the storage used to hold data that is awaiting
transfer from a computer or modem.


Output device
A device used to convert data from its bit-pattern representation in storage
to a form which can be used outside the computer system, such as a printer.


Output medium
The medium on which output data is represented, such as paper.


Output routine
A program routine or utility that organizes or performs an output.


Outspacing
The placing of extra space between characters in a DTP or document processor
program for aesthetic effect.


Overflow
That part of a unit of data that will not fit into a storage location intended
to receive it.


Overhead
In processing, the time or operations that are devoted to system functions
rather than the job in hand.


Overlay program
A program that has been divided into overlay segments and a control segment
usually because of memory limitations of the computer, common under MS-DOS on
IBM PC compatibles.


Overlay segment
A part of an overlay program that is intended to be loaded when it is required
during the execution of the program and overwritten when no longer required.


Overload
To exceed the designed work capacity of a system or functional unit or the
safe current carrying capacity of an electric circuit.


Overwrite
To write new data to a storage location already occupied with data thus
destroying it.


Overwrite mode
A program mode enabling the writing of characters over others and thus
replacing them, rather than writing in-between them as in Insert mode.


Owner
In a hierarchical structure, an entity that has some degree of control or
privilege with respect to entities (members) on a lower level. In a net data
structure, an entity that must be accessed first in order to access other
entities, such as the root directory of a drive before accessing a file in a
subdirectory.


O
78 entries
EOF