"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
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I
IBM
International Business Machines. The world's largest computer manufacturer.
IC
Integrated Circuit.
Icon
A graphic symbol or picture representing a function, file, folder or hardware,
such as a program file or a disk drive. In GEM, the mouse is used to point to
and click on icons to initiate a particular function or event. Desktop icons
normally consist of only two colours, the data and the mask colours and have a
normal state and a selected state, the latter being an inverse of the former.
On the Falcon and some replacement Desktops, animated icons are used, where
each icon can have colour data for any mode with 16 or more colours and where
the selected and normal states are stored separately and given different
styles. This enables a switch from one form to another when the icon is
selected, giving a simple animation.
ID
IDentification. A group of characters that uniquely identifies something, such
as a computer network user.
IDE
Intelligent Drive Electronics or Integrated Drive Electronics. A method of
connecting disk drives (principally hard disks) to a computer. IDE drives have
the controller circuit included with the drive electronics and not on a
separate circuit board which results in simple, quick and cheap drive
installation. The Falcon030 is fitted with an internal IDE connector for a
small 2.5 inch internal hard disk.
Idle
A functional unit that is ready to operate, awaiting inputs and producing no
output.
IEEE
Institute of Electrical and Electronic Engineers. An organization which is
responsible for setting standards on some electrical components and
interfaces.
IFF
Interchange File Format. A graphic image file format used on Amiga computers
and some ST programs.
IKBD
Intelligent KeyBoarD. The keyboard, mouse and joystick controlling hardware of
the ST-Falcon range. The keyboard transmits encoded make/break key scan codes
with two key rollover, mouse/trackball data, joystick data, and the time of
day. The keyboard receives commands and sends data via a bidirectional
communication implemented with a MC6850 ACIA. The data transfer rate is 7812.5
bps. All keyboard functions are performed by a HD6301 8-bit microprocessor.
See ACIA and HD6301.
ILBM
InterLeaved BitMap. A bitmap graphics file format used on Amiga computers.
Illegal
Not interpretable or recognized in the system in which it occurs.
Illegal instruction
A processor exception that occurs when an instruction is encountered by a
processor that is not in its instruction set. This may happen if a program
corrupts some memory locations containing previously valid instructions. See
Exception vectors, Bombs.
Image
A visually interpretable representation as displayed or printed. Also, a file
containing the exact duplication of a part of memory, such as a disk file
version of ROM code.
Image processing
The use of computers to analyse, enhance and interpret images.
IMG file
A bit-image graphics file with an .IMG file name extender primarily associated
with the GEM operating system. The standard was set by Digital Research and
has the advantage of being able to save images larger than the screen size
(not possible with Degas format) and an in-built compression to make file
sizes smaller.
IMHO
In My Humble Opinion. Commonly used shorthand in e-mail and other messages.
Immediate access storage
Random access or direct access storage.
Immunizer
A program to 'immunize' disks from virus attack by placing a safe boot sector
program on the disk where a virus would otherwise exist and thus preventing
its use by a boot sector virus. Such methods are by no means infallible.
IMO
In My Opinion. Commonly used shorthand in e-mail and other messages.
Impact printer
A printer that strikes pins or an embossed type font against inked ribbons
onto paper. Such printers are usually noisy and intermediate in speed, but
cheap and in the case of dot matrix printers, versatile producing medium
quality output.
Implicit address
In assembly language source code, a symbolic address that translates into an
operand address in object code.
Import
To load text or images created elsewhere into an application for processing,
such as importing a text file into a DTP program.
IMVHO
In My Very Humble Opinion. Commonly used shorthand in e-mail and other
messages.
In-house
Something that is done on the users' premises and by their own staff.
Inactive
Idle, out of service, or infrequently used.
Include file
An external file, such as C header files, for inclusion in program source code
upon compilation.
Increment
To add, usually one, to a number in a sequence of such additions.
Incremental backup
A backup procedure where, on seeing the archive bit of a file as being set,
the backup program includes that file in the backup procedure, therefore only
backing up those files which are different to those of the last backup
operation. Once a file is stored in this way, the original file has the
archive bit reset which doesn't become set again until that file is written to
once more.
Indent
To set the margins of a section of printed text within the default margins of
the page. In some cases the first line only of a paragraph is indented on the
left margin, whilst it is common to highlight certain paragraphs (say, a
quotation) by setting in both margins of the whole paragraph.
Index
A list of items and their locations maintained for access and manipulation
purposes, i.e. of records in a database file or files in a directory. Also, a
subscript, a value used to identify a location in an array.
Indirect address
In program source code or object code, where the address given in the address
part of an instruction is not the address of the required operand. Instead,
the address part is the address of the location which contains the required
address, that is, it is a pointer to the required value.
Indirection
The use of indirect addresses or pointers.
Infix notation
The usual way of expressing mathematical relationships where the operators are
placed between the operands (2 + 2 =) rather than separately, as in Polish
Notation (2 2 +=) for instance.
Information
An element of knowledge. Computers are incapable of processing information,
only processing and outputting data which, when examined and analysed by
humans and given meaning, provides information.
Information line
An optional line under a GEM window's move bar showing program specified
information for the user. On the Desktop, the information line in a directory
window will show how many bytes are used by the items listed or how many items
are present.
Information retrieval
A term applied to a system in which large amounts of data are catalogued and
arranged for selective access to meet different requirements.
Information system
An interactive network system providing users with access to data and
information from various sources, such as CompuServe.
Information technology - IT
The field of creating systems and devices for use in the dissemination of data
and information, such as Viewdata, Teletext or a company database.
Initialize
Establishing prescribed starting conditions before executing a program usually
from within the program itself. Typically it may mean the setting of flags,
the allocation of memory, resetting counts etc. Also, it is the correct term
for the disk formatting procedure. See Format.
Inkjet printer
A printer that forms dot matrix characters by applying ejected droplets of ink
to paper. The print head consists of a number of nozzles surrounded by
piezoelectric elements which heat up and vaporize a small quantity of ink
which in turn blows a drop of liquid ink out onto the paper. The technology of
these printers has improved over the last few years giving quick, quiet and
good quality results, almost on a par with cheaper laser printers. Colour
inkjet printers are now affordable producing excellent results.
In-line code
A section of assembly language code placed within high-level language source
code.
Input
That which is, or intended to be, received by a device or the movement of data
to memory from a storage or input device.
Input buffer
A section of memory used to store inputs awaiting processing, such as in a
communications link or the keyboard buffer of a computer.
Input device
A device used to convert data from some other form into bit-patterns that can
be written to the computer system, e.g. a mouse or scanner.
Input field
An area of the display screen in which the user can enter or modify data, such
as the file name field in the file selector.
Input/output - I/O, IO
The process of transferring data between the CPU and its memory and an
external device or semiconductor, termed the input/output device.
Input/output device
A device used to handle transfers to and from main storage, such as a disk
drive controller or a UART chip.
Input/output map
See Memory map.
Input routine
A program routine that handles the input into the computer's memory.
Inquiry functions
A set of GEMDOS VDI functions providing the data to enable programmers to
write GEM programs for any GEM environment. Such a function may inform the
program as to the size of the screen or window, for instance.
Insert
To place an item in the correct sequence among others moving them as
necessary, e.g. a word in a sentence or a record in a database.
Insert key
An application defined Atari keyboard key usually for switching between
'Insert' and 'Overwrite' modes or inserting a space character within a line of
text.
Insert mode
A program mode enabling the insertion of characters between others rather than
overwriting them, and a common function in text editors.
Install
Setting up a program, data or device ready for use. This usually means copying
the master disk files onto a hard disk or working copy floppy disks into the
correct directories, setting up any necessary environment variables and
allocating any system resources to the program. Some large program packages
can have special programs that carry out most, if not all, of these procedures
for the user.
Instruction
A program element specifying an operation to be performed on or with data. In
high-level languages the term 'statement' may be preferred. Instructions
typically consist of an operator and one or more operands.
Instruction set
A processor's set of instructions held in control unit memory defining all the
operations it can perform.
Insulation
Non-conducting material used to isolate electrical conductors from contact
with other conductors or the environment. It normally takes the form of a
plastic coating on wire.
Insulation displacement
A method of making electrical contact with the conductors of an insulated wire
that does not involve removing the insulation. The usual method is to drive
pins through the insulation and commonly used to connect plugs on to ribbon
cable. The method is easy but not guaranteed to make good contacts over time.
Integer
A 'whole' number without a fractional part, e.g. 2 or -4 rather than 1.34.
Integrated
Separate items included and functioning as a single unit.
Integrated circuit - IC
A minute electronic circuit on which the components, such as transistors,
diodes and resistors are produced on a single semiconductor substrate (chip of
silicon) by a process involving masking, etching and diffusion. Such a device
is packaged into a resin plastic holder with metal pins which are connected to
the circuit and enable the IC to be conveniently handled and connected to a
circuit board.
Integrity
A term applied to data when considering its accuracy, validity or freedom from
corruption.
Intel
The designers and makers of semiconductors, especially the 80x86 series
processors found in PCs.
Intelligent
Also smart. Devices which can control and modify themselves using built-in
instructions, usually on ROMs. Unintelligent devices are termed 'dumb'. For
instance, most laser printers are intelligent in that they have processors and
memory to handle the processing of the image onto paper, thus relieving the
CPU of the attached computer. The Atari laser printers are dumb, without any
processing ability or memory.
Intensity
The amount of light emitted by a display, its brightness.
Interactive
A term applied to software which holds a 'dialogue' or 'conversation' with the
user, responding appropriately to the user's input.
Interblock gap - IBG
In magnetizable surface storage, a space between blocks of data that is not
recorded with it and acts as a block delimiter.
Interchange
To transpose. Also, a sequence of related messages between a computer program
and a user in a conversational mode.
Interface
The boundary between connected devices and systems with different
characteristics, such as the printer parallel interface port. The term may be
applied to a cable or connector, a device that carries out some data
conversion operation or may even be the software front end of an operating
system, such as a graphic user interface.
Interlace sync
In a screen display, a method of enhancing the resolution by introducing a
delay in the beginning of alternate vertical scans in order to displace the
scan by one line to double the number of vertical dots. Thus, the screen shows
the odd numbered lines on one vertical scan and then the even numbered lines
on the following refresh allowing for persistence of the phosphors to hold the
first scan on the screen, thus interlacing the two to get twice as many lines.
However, if the phosphors stay bright too long then moving images across the
screen, such as mouse pointers, will blur. If the phosphor has a low
persistence then flickering of the image occurs as alternate lines of
phosphors fade and brighten at regular intervals. Because it takes two screen
refreshes to draw one whole screen, the total frame frequency is halved and
unless the frame frequency is very high, this flickering of interlaced
displays is their biggest disadvantage. The human eye can perceive flickering
at any frequency below about 50 Hz although this does vary, meaning that a
non-interlaced screen needs a refresh rate of 100 Hz to achieve a stable
display when using an interlaced mode.
Interleave
To combine two or more groups of items in such a way that those items are
interspersed but with each group retaining their individual identities. The
term is commonly applied to a method of disk formatting where the sectors on
the tracks of disks are initialized in a different order on each track, that
order depending on the speed at which the drive can read data. An interleave
of one means that the sectors are arranged constitutively (1, 2, 3, 4 etc.).
An interleave of two means that consecutive sectors have another one between
them (1, 10, 2, 11, 3, 12 etc.) and an interleave of three places two sectors
between consecutive ones and so on. This interleave determines the maximum
speed that data can be recovered by the drive. Some drives and controllers
can't read the data fast enough and so the next sector will pass the head
before the controller is ready for it. The controller will have to wait a full
revolution of the disk for the sector to come round again. The extra sectors
between the sectors provide enough of a delay to allow both sectors to be read
in a single revolution. This non-consecutive arrangement of sectors is often
called a 'twisted' format. Changing the interleave factor on hard disks can
greatly increase their performance. This is also beneficial on floppy disks.
The Desktop disk format since TOS 1.2 has been of the twisted or spiral form
and was improved for double-sided disks from TOS 1.4 onwards. See Twisted
format.
Intermediate language
A language, other than machine code, produced by a compiler as a step in
compiling a high-level language to machine code.
Internal call
A call to a sequence of instructions that were compiled at the same time as
the sequence that called it, within the same program.
Internet
The Internet is a large network of networks and is what you get when you join
together all the thousands of academic, commercial and military networks
around the world interconnected together in real-time usually using the TCP/IP
protocol suite.
It can be seen as a set of hardware and the links between them - a physical
entity. It can also be described as a set of agreed protocols and the software
controlling the network. Perhaps it is the electronic traffic, the postings,
messages, e-mail, reports etc. that are generated by the people using it.
Maybe it is just a set of shared attitudes about interconnecting and
communications - an ideology.
Generally, there are five things that you can do on the Internet - e-mail;
conferences or newsgroups where discussions take place; file transfers (ftp),
remote computing (telnet) and information gathering (gopher, WWW). See TCP/IP,
E-mail, FTP, Telnet, Newsgroups, USENET, Gopher, WWW.
Inter-network
The passing of data between different networks often through one particular
node and requiring some conversion.
Interpret
To evaluate or to translate. In program source code, to translate and execute
statements one at a time in sequence.
Interpreter
A program that translates and executes high-level language source code one
instruction at a time, usually without retaining the object code. Such methods
of program translation were common in home micros that had a built-in
language, such as BASIC on the BBC or Spectrum. Interpreted programs run
slower than compiled ones but have the advantage of being more easily debugged
and quicker to use. They are also not very portable, as every user has to have
a copy of the interpreter to run them. See Compiler.
Interprogram communication
The means by which one active program communicates with another in memory. The
term can apply to the passing of parameters between an accessory and a
program, or between a GEM program and the AES screen manager when such
functions as evnt_mesag() or evnt_multi() are used. The means of communication
is usually a mutually accessible buffer into which one program writes some
data and from which the other reads. Such unidirectional buffers are termed
pipes and are commonly available in operating systems. See Pipes.
Interrogate
To identify a required item of data, usually by a search.
Interrogation
The process of identifying and locating a required item of data from a data
block. Also, the process of requesting a terminal or data station in a
communications network to identify itself.
Interrupt
To stop the execution of a program and transfer control to another one whilst
retaining the values necessary to resume the execution. The cause of the
interrupt may be internal to the program, such as exiting from a loop of
instructions or external from it, such as from a peripheral device
malfunction. See Exception.
Table I1: Interrupt Assignments - ST/STE
Level Definition
Highest
7 Non-maskable interrupt - NMI
6 MFP 68901
5
4 VBL - Vertical blanking sync
3
2 HBL - Horizontal blanking sync
1
Lowest
NOTE: only interrupt priority level inputs 1 and 2 are used.
Table I2: MFP 68901 Interrupt Control
Priority Used Definition
Highest
15 no Monochrome monitor detect/DMA sound complete
14 no RS-232 ring indicator
13 no DMA sound event counter - Timer A
12 yes RS-232 receive buffer full
11 yes RS-232 receive error
10 yes RS-232 transmit buffer empty
9 yes RS-232 transmit error
8 no Horizontal blanking counter - Timer B
7 no Floppy disk drive controller and DMA
6 yes Keyboard and MIDI ACIAs
5 yes 200 Hz system clock - Timer C
4 no RS-232 baud rate generator - Timer D
3 no BitBLT complete
2 yes RS-232 clear to send
1 no RS-232 data carrier detect
0 no Parallel port BUSY
Lowest
NOTE: Not all these interrupts are used by TOS. Some that can be used and
their meanings depend on the version of TOS. Those not used by TOS can be used
by the user, such as level 15 which can be used by interrupt-driven DMA sound
drivers and level 13 used when producing DMA sound by normal methods. The
MC6850 ACIA Interrupt Request status bit must be tested to differentiate
between keyboard and MIDI interrupts.
Table I3: Interrupt Assignments - TT
Level System VME
Highest
7 VME bus SYSFAIL IRQ7
6 MFP 68901 IRQ6
5 SCC IRQ5
4 VBL IRQ4
3 VME interrupter IRQ3
2 HBL IRQ2
1 System interrupter IRQ1
Lowest
Within each level, a system interrupt has priority over a VME interrupt.
Within the shared levels 5 and 6 interrupts, the part on the motherboard has
priority over the VME interrupt. The VME interrupts use their interrupt status
byte as their interrupt vector. On level 3, the system interrupt mask must be
enabled for the level 3 VME interrupt to actually be generated.
Table I4: MFP-ST 68901 Interrupt Control
Priority Used Definition
Highest
15 no Monochrome monitor detect/DMA sound complete
14 no RS-232 ring indicator
13 no DMA sound event counter - Timer A
12 yes RS-232 receive buffer full
11 yes RS-232 receive error
10 yes RS-232 transmit buffer empty
9 yes RS-232 transmit error
8 no Horizontal blanking counter - Timer B
7 no Floppy disk drive controller and DMA
6 yes Keyboard and MIDI ACIAs
5 yes 200 Hz system clock - Timer C
4 no RS-232 baud rate generator - Timer D
3 no reserved
2 yes RS-232 clear to send
1 no RS-232 data carrier detect
0 no Parallel port BUSY
Lowest
Table I5: MFP-2 68901 Interrupt Control
Priority Definition
Highest
15 SCSI controller IRQ (active high)
14 Real-time clock IRQ (active low)
13 Timer A
12 RS-232 receive buffer full
11 RS-232 receive error
10 RS-232 transmit buffer empty
9 RS-232 transmit error
8 Timer B
7 SCSI DMAC interrupt
6 reserved
5 Timer C
4 Timer D
3 SCC B ring indicator
2 SCC DMAC interrupt (active low)
1 General purpose I/O pin
0 General purpose I/O pin
Lowest
Interrupt driven
An operating system that allows multitasking by allowing processing to
continue for one program until an interrupt occurs and then changing
processing to another program. TOS is such an operating system where several
TSR type programs (those present in the AUTO folder or accessories) can appear
to run concurrently.
Invalid
Something that cannot be used because of failure to meet established criteria.
Inverse video
Where the background and foreground colours on a VDU screen are interchanged,
thus allowing for some rudimentary highlighting especially on monochrome
displays.
Invert
To turn an item up-side-down or to reverse the screen colours.
Inverted tree
A tree data structure where the root is shown at the top. It is the usual way
of representing hierarchical organizations and data structures.
Invoke
To cause to be executed. To call a program or routine.
I/O, IO
Input/Output.
I/O Map
See Memory map.
IP
Internet Protocol. See TCP/IP.
IPC
Inter-Program Communication.
IPX
Internet Package eXchange. A protocol used by the Novell company which governs
the connections between PCs in a network.
IRC
Internet Relay Chat. An Internet service which allows a user to 'talk' (send
electronic messages) to a group of others in real-time regardless of
geographic location.
IRQ
Interrupt ReQuest. While a microprocessor is processing data or instructions,
it is important that peripheral devices, such as disk drives, have some means
of interrupting the processor requesting that it services that device instead.
The IRQ is a signal from the external device to one of the pins on the
processor. The microprocessor can refuse such a request if the priority of the
task in hand is higher than that requested from the external device. To get
around this, processors also have a non-maskable interrupt which is always
acknowledged by the processor.
ISA
Industry Standard Architecture. The expansion slot connector found on IBM PC,
XT and AT computers and clones which allow daughter boards to be plugged into
the motherboard. It was originally designed to handle 8-bit data transfers but
was extended to sixteen bits with the IBM AT.
ISDN
Integrated Services Digital Network. The digital telephone network in the UK
extended into the home or workplace replacing the normal analogue subscriber
line with a digital one. There are channels for digitized speech at 64 Kbits
per second and a control channel at 8 Kbps which can be used for information
services to computers.
ISO
International Organization for Standardization. An organization of member
countries promoting the development and use of product and terminology
standards, such as with computer languages, e.g. C.
ISO-7
A 7-bit code for data interchange which is the same as ASCII except that ten
characters are optionally allocated to national characters.
ISTR
I Seem To Recall. Commonly used shorthand in e-mail and other messages.
Italic
A style of text characterized (among other attributes) by slanting to the
right and having a cursive form.
Item
The smallest meaningful elements in a larger structure, such as in a menu or
record field. In a GEM program "File" menu, "Load..." is an item as is the
word 'Sarah' in a database name field containing 'Sarah Jane Blake'.
Item selector
The file selector, an editable dialog box used for selecting files for loading
and saving whilst using an application.
Iteration
The use of a loop or repetition of a sequence of instructions in order to
perform an operation with different operands.
ITU
International Telecommunications Union. Anglicization of the proper French
name of the Union Internationale des T‚l‚communications (UIT), Geneva,
Switzerland. ITU is the treaty-established world centre for agreements on
telecommunications technical and operating standards, such as the V series
standards, and is a constituent body of the United Nations, engaging also in
international development and education concerning telecommunications.
ITW
In The World. Commonly used shorthand in e-mail and other messages.
IYKWIM
If You Know What I Mean. Commonly used shorthand in e-mail and other messages.
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106 entries
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