"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
*****************************************************************************


P


p
Pico. Prefix meaning a trillionth (10^-12).


Pack
To reduce the storage space of a file by data compression techniques, such as 
in ARC and LHARC (.LZH) files.


Package
A group of related items sold at a single, all-inclusive price. Also, the 
enclosure and terminal arrangement of a semiconductor device.


Packet
A unit of data with routing and control characters intended to be transmitted 
as a unit, especially in a packet switching system. That packet may consist of 
many messages from one particular node to others in the network.


Packet assembly/disassembly facilities - PAD
The facilities of a packet switching system that provide for the connection of 
modems and computers.


Packet switching system - PSS
A data network in which users communicate by means of packets of data of 
standard format routed by linked exchanges and PADs and using high-speed 
telephone circuits.


Padding
A process of adding pad characters (usually a nul character) to data items or 
storage locations often to bring it up to some predetermined length.


Page
A sheet of continuous stationery or a single side of a sheet of paper. Also, 
the data displayed at one time on a display screen. In some operating systems, 
a fixed number of bytes that is identifiable as a unit, a standard unit of 
storage in a virtual storage system.


Page description language - PDL
See PDL.


Page printer
A printer capable of printing an entire page in one pass, such as a laser 
printer.


Paging
The operation of swapping pages of memory between primary and secondary 
storage, such as between RAM and disk or between primary RAM and extended RAM 
not directly addressable by the CPU i.e. the memory over 640 K in PC-ATs.


Painting program
A program that enables a user to produce a picture on the screen usually with 
the aid of a mouse and certain software tools, such as pen, brush, air-brush, 
fill, line, box etc. The resulting picture is a bitmap image where individual 
pixels are individually turned on or off or in one of many different colour 
states. Such an image has all the disadvantages of bitmap images compared to 
vector graphics used in drawing programs. See Bitmap image, Drawing programs, 
Vector image, GEM metafile.


PAL
Phase Alternating Line. The television standard used in the UK and most of 
Europe. See NTSC.


PAL
Programmable Array Logic. A complex logic integrated circuit which, with the 
aid of development software and a PAL programming device, a hardware 
programmer can turn into a custom logic integrated circuit for a specific 
task. One such device can replace a large number of conventional 74 or 4000 
series logic chips thus decreasing production costs. The construction of a PAL 
offers less flexibility than a PLA but they are generally faster in operation. 
The Atari custom chips such as the GLUE, MMU etc. are PALs.


Paperless office
The future that never happened, where all records are held in computer-
readable form, inputs and outputs are all electronic and all operations 
performed by computers. Paper was to be redundant, whereas in practice it has 
never been used - and wasted - so much.


Parallel
Independent operations performed simultaneously or within the same time 
period.


Parallel computer
A computer with multiple processors and the capability of parallel processing.


Parallel port
A device port capable of transmitting eight bits of data simultaneously. Often 
used for connection to a printer. See Printer port.


Parallel processing
Where a unit of processing is divided into smaller units all of which are 
executed at the same time using multiple sets of facilities, such as 
processors, RAM, I/O channels etc.


Parallel transfer
A bit-parallel transfer, the simultaneous transfer of all the bits of a word, 
such as from RAM to the CPU.


Parameter
An input value used to determine how processing is to be performed or the 
results produced. It can be inputted by a programmer, a user, by the operating 
system or by a program. Atari .TTP programs are designed to take parameters 
entered by the user to affect their mode of operation. For instance, in the 
LHARC file compression program the parameters -x archive.lzh will cause the 
program to extract all the files from the file archive.lzh and perform no 
other operations.


Parent
The previous generation of a file. Also, a GEM resource file object that 
contains others within its bounds.


Parity
A system of detecting errors in data transmissions that consists of 
selectively adding a 1-bit to bit-patterns so that the bit-pattern has an odd 
number of 1-bits (odd parity) or an even number (even parity). The receiving 
hardware checks the number of 1-bits and indicates an error if a pattern with 
an even number of 1-bits is found in an odd parity system and vice versa. This 
system is increasingly becoming redundant because of its poor accuracy over 
high-speed and noisy lines and the introduction of better methods.


Parity bit
A 1-bit used in parity checking.


Parity check
A redundancy check in a parity system. See Parity.


Parking
To move the read/write heads of a hard disk drive off the formatted used 
surface of the disks to an unused part, usually at the outer edge. This can be 
achieved either by software and a user command, or more usually, automatically 
when the drive is switched off. The distance between a head and the surface of 
the disk is extremely small and any shocks and vibrations could hit that head 
against the surface, damaging it and corrupting the data stored there. As this 
is likely to happen when the hard disk is switched off and in transport, a 
facility to move the heads away from the disk surface is mandatory.


Parsing
The compiler operation of breaking down instructions into their individual 
elements and identifying them in terms of the programming language for their 
legality. This process also occurs when passing parameters to programs.


Partition
An operating system boundary within large storage media separating it into 
smaller units often with different purposes, priorities or access rights, such 
as dividing a large hard disk into separate virtual disks. The unit of storage 
itself is frequently called a partition.


Pascal
A structured high-level language, often used in educational establishments.


Pass
One cycle of a multi-cycle operation, such as in a two-pass compilation.


Password
A group of characters associated with a unit of code, data or facilities in a 
system, giving access to them. A program or, more usually, a user must provide 
an identical string of characters in order to be allowed access.


Patch
A small section of program code inserted into a previously written and 
compiled sequence to make an alteration to or correct an error in it.


Path
That which carries data or signals between two locations, a line, circuit, 
channel, link, bus, highway or cable. Also, a sequence used to locate 
particular data in a data structure, such as a tree. Such a tree may be the 
hierarchical data structure of a disk's directory contents. Also, the route 
between a sending and a receiving station as defined by the nodes through 
which a message or data packet must pass in a communications network.


Path name
A list of items used to locate files in a hierarchical filing system. It 
consists of a disk identifier and a string of folders separated by backslashes 
and may contain a filespec, such as D:\PROTEXT\DOCS\*.* which points to all 
the files in the DOCS subdirectory within the PROTEXT directory on the disk 
drive D:.


PC
Personal Computer. The first IBM series of desktop computers running under PC-
DOS launched in 1981. The term is practically synonymous for any microcomputer 
although it most commonly denotes any of the IBM PC compatible family of 
desktop computers running under the MS-DOS (or compatible) operating system.


PC
Program Counter. The current address register of a processor.


PCB
Printed Circuit Board.


PC-DOS
The original operating system for IBM's PC, later released by Microsoft as MS-
DOS for IBM PC clones.


PCL
Printer Control Language. A system devised by Hewlett-Packard to control the 
output of laser printers and generally considered a standard.


PCM
Pulse Code Modulation. A method of modulation and multiplexing in which an 
analogue wave is transmitted by means of digital bit-patterns, each of which 
represents the amplitude of the wave at a particular sampling point in time. 
The type of sound system introduced on the STE uses this method with an 8-bit 
sampling rate, each byte representing one of 256 (-128 to +128) different 
amplitude levels. See DMA sound.


PCMCIA
Personal Computer Memory Card International Association. A committee 
responsible for the standard format for the large capacity, credit card-sized 
plug-in memories that are used with some portable computers. Such cards were 
to be used on the Atari Stylus.


PD
Public Domain.


PDL
Page Description Language or Page Definition Language. A system of controlling 
a printer where the details of the whole page image is written in ASCII text 
and sent to the printer before printing starts and where the printer's 
processor performs the necessary operations to translate the data into a 
bitmapped image for printing. PostScript is the most common PDL.


Performance
A term used to indicate both speed and reliability.


Peripheral
A separate functional unit that makes and/or receives data transfers with 
initiation by the CPU. Usually storage and I/O devices, such as printers.


Personal computer
A small, inexpensive microprocessor-based computer designed for desktop 
business use or for the home and hobbyist. Personal computers are rapidly 
replacing dumb terminals in multi-user networks run on mini and mainframes. 
Although the specification for a personal computer changes rapidly, they 
invariably have a keyboard and monitor, disk drive storage and at least 512 K 
to 1 Mb of RAM. The microprocessors are usually of the Intel 80x86 or Motorola 
680x0 series, the most common operating system being MS-DOS.


PGA
Pin Grid Array. An integrated circuit package where the pins for connection to 
the circuit board are arranged in a grid pattern underneath the square chip 
package. Such an arrangement is necessary because of the increasing number of 
pins required for modern chips, such as the Intel 80486DX which has 162 pins.


Phase
The time relationship between two waves (assumed to be sine waves) of the same 
frequency. If the two waves go from positive and negative and back again in 
the same time they are said to be 'in phase'. If they do not go through their 
cycles concurrently they are 'out of phase' and the amount they are out is 
measured in degrees.


Phase locked
A term applied to a device or operation that obtains its timing from input 
signals and which incorporates a feedback circuit to maintain synchronization.


Phase locked loop - PLL
See Phase locked.


Phase shift modulation
A method of modulation in which data is transmitted as different amounts of 
change of phase of a carrier wave. Such methods can transmit two or three bits 
of data for each Baud, and by using two different amplitudes four bits can be 
transmitted per line transition. This and its variations are the common ways 
of transmitting data with modems at high speed.


Phosphors
The interior coating of a CRT screen that emits light when an electron beam 
hits it.


Physbase
A function that returns the address of the base of the physical screen of the 
ST-Falcon range, the one actually displayed. Normally this is the same address 
as pointed to by Logbase() but this is not required. See Logbase.


Physical
Real or hardware, not virtual.


Physical address
A hardware address and not a virtual one.


Physical storage
Real and actual storage not virtual storage.


Pica
A typesetting measurement equal to twelve points (about one-sixth of an inch).


Pico
Prefix meaning a trillionth (10^-12).


PIL
Page Interchange Language. A system that uses ASCII text files to describe the 
layout of a document containing different fonts and images, so that such 
documents can be transferred between different DTP programs.


PIM
Personal Integrated Media. Atari's new catch phrase to describe the Falcon030 
computer - the first PIM system.


Pin
A conductor of an integrated circuit, one of its legs. Also, a tooth on a 
sprocket of a printer's tractor feed or the striking needle element of a dot 
matrix printer that forms the dots on paper.


Pinout
A diagram or table showing the circuit functions of the connector pins in a 
device.


Pipe
A means of interprogram communication where a buffer is set aside to accept 
output from one process and is used as the input to another. This process is 
commonly used in operating systems, especially those with a CLI, such as MS-
DOS and UNIX. The vertical bar character | is normally used to signify the 
pipe process. For instance, the command ls -lt | head in the Mintshel 
environment under MultiTOS demonstrates a pipeline. The first stage of the 
pipeline is the program ls which has -lt as its argument. That is, "list 
directory, long form, sorted by date (most recent first)". The output of ls is 
passed as input to the next stage of the pipeline which is head. This program 
displays only the first ten lines of its input. The resulting output from this 
pipeline is, therefore, a listing of the ten most-recent files in the current 
directory. See Interprogram communication.


Pipeline
In a processing unit, a sequence of registers each specializing in certain 
operations and capable of performing some phase of instruction execution and 
passing the instruction and partial results on to the next register in the 
sequence. Once the first register has performed its task, it receives the 
next, so that in any one processor several operations could be done 
simultaneously. Also, see Pipe.


Pitch
The number of physical units per length, as in a pitch of twelve characters 
per inch in monospaced printing.


Pixel
PICture ELement. The smallest addressable point in a graphics display. The 
greater the number of pixels, the greater the resolution. The closer together 
they are to each other, the greater the density and picture quality. Standard 
monitors have densities of around 70-90 dpi.


PL/1
Programming Language 1. Early business and scientific programming language.


PLA
Programmable Logic Array. A complex logic integrated circuit which, with the 
aid of development software, a hardware programmer can turn into a custom 
logic IC for a specific task. One such device can replace a large number of 
conventional 74 or 4000 series logic integrated circuits thus decreasing 
production costs. The construction of a PLA offers greater flexibility than a 
PAL.


Platen
A surface against which the paper and ribbon are struck by an element in an 
impact printer.


Platter
A single hard magnetic disk, usually one of a stack in any disk drive unit.


PLCC
Plastic Leadless Chip Carrier. A method of packaging complex integrated 
circuits that uses terminals on the four sides of the square chip to make 
contact with the inside edges of the chip carrier which is mounted on the 
circuit board. The MMU and GLUE chips in a ST use such a method.


Plex
Synonymous with net.


PLL
Phase Locked Loop.


Plot
To place graphic images on paper, the function of a plotter.


Plotter
An output device placing two-dimensional patterns on paper, usually by a 
moving pen, and sometimes moving paper, arrangement. Typically used to plot 
graphs and CAD drawings.


Point
A vertical typesetting measurement equal to about 1/72 of an inch (0.013837 
inch or 72.27 points to an inch).


Pointer
The address of one storage location as held in another storage location. Also, 
a mouse pointer.


Pointer array
A table or array of pointers.


Pointer chain
A series of pointers that establishes a path of control.


Polish notation
A method of mathematical operations where the operators are placed in the 
order in which they will be dealt with rather than in the order they occur. 
The collected operators are placed before the operands, but after in reverse 
Polish notation, as in the expression 3 x (A / D) which in reverse Polish 
notation would be AD3/x.


Poll
To send a short message from a data network master station to each node to 
invite them to send any messages they may have.


Polygon
A 'closed' multiple line graphic.


Polyline
A multiple line graphic which is not 'closed' at the ends.


POOLFIX3.PRG
An official freeware Atari patch program for TOS 1.4, 1.6 and 1.62 which fixes 
a bug with the GEMDOS Malloc() function. POOLFIX and POOLFIX2 are bugged and 
should not be used. POOLFIX4 was released by Claus Brod to fix a problem 
Atari's version had with some hard disk drivers. See Forty folder bug.


Pop
To remove an item from the top of a push-down stack.


POP
Point Of Presence. An access node for a dial-up service provider that is 
remote from its main installation but local (and therefore at local call 
rates) to some of its users.


Pop-up menu
A menu in a GUI/WIMP environment that appears elsewhere than at the top of the 
screen, and usually at the position of the mouse pointer when called by a 
mouse button click.


Port
An interface by which data enters and/or leaves a functional unit, typically a 
multi-pin electrical connector or coaxial cable termination. Also, in a 
network such as the Internet, an ID that specifies a particular application or 
server on a machine, especially those that need to provide general access for 
account holders and specific access to the public. Telnet, for instance, is 
normally on port 23.


Portfolio Pocket PC
An Atari-badged hand-held computer, almost IBM PC compatible and designed by 
DIP in the UK. It uses a clam-shell design with a keyboard on one half and a 
40 column by eight line supertwist LCD screen on the other. This screen has 
the option to window a full 80 x 25 screen. The graphics display is 240 x 64 
pixels. The processor is a slow 4.9152 MHz Intel 80C88 and there is a 256 K 
ROM containing the DOS, BIOS and a suite of built-in applications including an 
address book, dialler, time manager, calculator, text processor and a Lotus 1-
2-3 compatible spreadsheet. DOS is a somewhat dated MS-DOS 2.11 compatible 
version. 128 K of RAM is also fitted as standard. Battery backed, credit card-
sized RAM cards are available in 64 K, 128 K, 256 K, 512 K and 1 Mb sizes 
which can be used to save data onto and for supplying additional applications 
on. A 60-pin expansion bus port is fitted for connection to a parallel or 
serial interface. The keyboard is a 63-key QWERTY, IBM BIOS compatible 
keyboard with a buried numeric keypad and function keys. One innovative 
feature is that the address book can output the dialling tone of a telephone 
number through a built-in loudspeaker which is held against the mouthpiece of 
a telephone for convenient dialling. The weight is about 450 g (1 lb) with 
batteries and its size is suitable for placing into an inside jacket pocket. 
It operates from three AA batteries or an optional mains adaptor.


Port width
The amount of data that can be transmitted simultaneously through a port.


Portability
The extent to which items, such as programs, can be used on or with other 
different systems. A language is said to be portable if its source code can be 
used with little or no modification on another computer of a different make, 
processor or operating system.


Porting
The act of transferring data or programs from one computer operating system to 
another including any modifications to get them to work on the new system.


Positional representation system
A numeration system where the digits have values depending on their position 
with respect to the other digits in the number. See Numeration system.


Positive
A number greater than zero. A terminal towards which electrons flow from the 
negative terminal on a circuit or battery.


Postfix notation
Reverse Polish notation.


Posting
A message sent to a USENET newsgroups or to any other public message area. 
Also, the act of sending a message.


Postmortem
An analysis of an operation performed after its completion and usually carried 
out to determine what happened.


PostScript
A complex page description language, seldom directly compiled by users but by 
programs, to produce output to paper. A PostScript file contains a description 
of a page which is translated and processed by a compatible printer which 
reconstructs the image for printing. It is intended to be device independent, 
being capable of producing the best results from a 9-pin dot matrix printer to 
a professional imagesetter. Although its use was available from day one on the 
Apple Macintosh, its appearance on the ST-Falcon range has almost been 
nonexistent until recently. SpeedoGDOS now supports PostScript Type 1 fonts.


Power
The value of an exponent, the number of times a number is multiplied by itself 
in exponentiation, as in 2^3 or 2 x 2 x 2. Also, a reference to the processing 
speed of a computer and the measurement of electricity in watts.


Power down
To make an orderly shutdown of a system.


Powerful
A term used to indicate relative capability or versatility.


Power Pad controller
A ten-key pad controller for the Jaguar games console.


Power supply unit - PSU
A device that provides the direct current voltages required by a functional 
unit. It typically contains a transformer that changes the mains alternating 
current voltage (240 V UK) to a lower direct current voltage suitable for the 
device which it serves, such as 3 A at 5 V (actual use 2.3 A) and 0.9 A at 12 
V (actual use 0.4 A) for the ST.


Power up
To supply electrical power to a functional unit or a system. In the latter, a 
series of these steps may have to be gone through before the whole system is 
functional.


PPM
Pages Per Minute. A measurement of the speed of operation of page printers, 
such as laser printers.


PPP
Point to Point Protocol. A new and conforming protocol that allows a computer 
to connect to the Internet and use the Internet Protocols (IP) using a modem 
and standard telephone line. Such connections are usually for stand-alone 
(unnetworked) PCs and made through a Service Provider. PPP connections have 
many advantages over SLIP ones which it is rapidly replacing. See TCP/IP, 
SLIP.


Preamble
A sequence at the beginning, such as the synchronizing and identification 
characters at the beginning of a block of transmitted data.


Precedence
The order in which items are processed or considered.


Precision
The accuracy of a number as limited by the maximum number of digits that can 
be used to express the fractional part. For instance, double precision 
indicates that a numeric value is held as two words and so accommodating more 
decimal places than with only one word.


Pre-emptive
A program or task that interrupts regular processing. Any true multitasking 
system is pre-emptive, as is MultiTOS and MagiC, because programs have to be 
processed on a single processor by interrupts. This means that a system 
doesn't have to wait for permission from a process or program before switching 
to another process. In this way, all processes get a share of the CPU although 
the priority of any task can be controlled by the user.


Prefix
A part that precedes another.


Pre-press
The production of textual and/or graphic material using DTP, image processing 
and other text processing software on a microcomputer for final output to a 
high resolution typesetting system.


Preset
A parameter provided prior to execution, often bound in the source code.


PRG
A GEM executable application file name extender. A program file.


Primary key
The main or only value by which a record is identified in a database.


Print
To convert data held in storage to a form represented by characters (or other 
marks) on paper.


Printable character
Any character that is not a control character, such as letters, numbers and 
punctuation marks.


Print control character
A control character that affects the printing process rather than the display, 
such as a line feed or Esc-E on an Epson compatible printer which switches on 
enhanced printing.


Printed circuit board - PCB
A thin board onto which copper tracks have been formed by photolithographic 
and etching processes and electronic elements have been soldered to form a 
circuit.


Printer
A device that inputs data in an electrical bit-pattern form and outputs onto 
paper, card or transparencies.


Printer driver
Any program that produces output to a printer has to have a means of 
communicating to each of the many different types of printers which use 
different command sequences to control them. The standard control codes for 
dot matrix printers are the Epson Esc control codes which work for most basic 
features, but all printers have additional ones in order to compete in a large 
market, such as more fonts, styles, higher graphics resolution, colour etc. As 
the file produced by any word processor or DTP program is constant the means 
of translating it into a form that a printer understands is left to individual 
interfaces called printer drivers, which sit between the program's output 
routines and the printer. Different programs require different printer 
drivers. Each program requires different drivers for different printers. There 
is no universal printer driver on the ST-Falcon range. Most programs will be 
packaged with different drivers, such as most programs using GDOS will provide 
drivers for NEC P, Epson FX80, BJ10, DeskJet 500, LaserJet, NB15 and SLM laser 
etc. These printer drivers are heavily coded and not capable of being altered 
by a user. However, most word processors use printer drivers and translators 
that are (or start out as) ASCII text files which can be edited by a user to 
exactly suit the needs of a particular printer. First Word Plus and Protext 
operate like this. A thorough understanding of the control codes of a printer 
and the design of a particular printer driver is necessary to tackle such a 
job.


Printer port
The ST-Falcon range printer port is controlled by the programmable sound 
generator chip, the YM-2149 chip which has, apart from its sound generating 
capabilities, two 8-bit bidirectional ports. These can be configured under 
software control to be input or output ports and can be used to communicate 
with the outside world beyond the use of printers, such as extra joystick 
ports, data input from remote sensors, robot control and data transfer between 
computers. The ST supplies the 8-bits of data from the data bus lines D8 to 
D15 to the YM-2149's D0 to D7 data lines. The STROBE signal is generated by 
software through the YM-2149 if the data is valid to the printer. The printer 
can respond with a BUSY signal (goes high) on pin 11 if it is already 
processing data or off-line. If BUSY is low, the YM-2149 sends the byte of 
data. A pulse on the ACKNLG line (pin 10) from the printer tells the computer 
that the printer is ready to accept another byte of data.


Print head
That part of a dot matrix printer (impact, thermal or inkjet) that forms the 
characters on paper.


Printout
The output from a printer.


Priority
An assigned value or rank that indicates when a particular item is to be dealt 
with in relation to other items awaiting attention or access to a resource. 
High priority items take precedence over low priority ones.


Privilege
An indication of the access rights of a user to data of a system.


Privilege violation
A processor exception error that occurs when a program is in user mode and 
tries to execute an instruction that is only allowed in supervisor mode. See 
Exception vectors, Bombs.


Procedure
A short subprogram that is called by name or label where required in source 
code and often from a library of such routines.


Process
To execute instructions or a program. Sometimes, those instructions 
themselves.


Processing
The operation of executing user programs with appropriate data.


Processing speed
The number of instructions executed per second by a CPU, usually measured in 
MIPS.


Processor
The element of a computer system that can interpret and execute instructions. 
See CPU and FPU.


Processor state save area
A small area of RAM where TOS stores some information about a program after a 
system crash. This is not cleared after a reset and can be examined after a 
crash to help identify the problem. A long is 32 bits and a word is sixteen 
bits.

  Table P1: Processor State Save Area

  Address   Name          Length
  in hex
  $380      proc_lives    long
            After a system crash, this value will be $12345678 if TOS was able
            to save the processor state in the following variables.
  $384      proc_dregs    8 longs
            The contents of the CPU registers D0 to D7.
  $3A4      proc_aregs    8 longs
            The contents of the CPU registers A0 to A7.
  $3C4      proc_pc       long
            The first byte contains the exception number that occurred.
  $3C8      proc_usp      long
            The contents of the CPU user stack pointer (USP).
  $3CC-
  $3EA      proc_stk      16 words
            The contents of the first 32 bytes of the supervisor mode stack
            which contains the Program Counter (PC), the address at which the
            program crashed.
  $3EC-
  $3FF      unassigned


Product
The result of a multiplication. Also, that which is produced or manufactured.


Profile
A list of features belonging to a particular item that may also identify it 
from another. A user's profile on a network may contain that person's access 
status, terminal settings, password and ID, personal details such as address 
and age, accounting details etc.


Program
One or more sequences of related instructions that, when executed, perform 
some function or operation. There are three main types of programs. 
Application programs or user programs perform work for a user. System programs 
form part of a computer's facilities including the operating system. Sequence 
control programs are found in non-computer devices, such as washing machines 
and printers and are used to control such devices. Programs are written by 
programmers using a programming language. The resulting source code is 
converted into a program by compilers. These types of programs are termed 
software and are typically stored on disks or tape. Some programs and 
especially sequence control ones, are stored in ROMs and are termed firmware.


Program block
A division of a program written in a block-structured language.


Program counter - PC
A processor register that holds the address of the next instruction to be 
obeyed after the instruction in the instruction register.


Program development
The process of producing a program from initial design to release.


Program file
A disk file containing an executable program. Double-clicking on a program 
file icon or its name in a directory window will execute it. Accessories are 
also program files but cannot be launched like this except under MultiTOS.


Program header
A block of data stored at the beginning of GEMDOS executable files, i.e. those 
with .PRG, .APP, .TOS, .TTP and .GTP extenders, which contains important 
information required by GEMDOS for the successful running of that program.

  Table P2: Program Header

  Offset   Size   Meaning
  $00      Word   Magic number, always set to $601A for GEMDOS programs
  $02      Long   Length of TEXT segment in bytes
  $06      Long   Length of DATA segment in bytes
  $0A      Long   Length of BSS segment in bytes
  $0E      Long   Length of symbol table in bytes
  $12      Long   Reserved
  $16      Long   Program flags - see below
  $1A      Word   Relocation table flag ABSCODE. A value of $0000 if there is
                  a relocation table, non-zero if not.

  The program flags long word:
  Bit
   0       Fastload bit: If set, only the program's BSS is cleared. If zero,
           then the whole of the TPA is cleared. Introduced with TOS 1.4.
   1       Alternative RAM Load. If set, program is loaded into Alternative,
           TT RAM. TT only.
   2       Alternative RAM Malloc(). If set, program's Malloc() calls are
           satisfied from TT RAM. TT only.
  28-31:   TPAsize. The value here indicates how much Alternative RAM the
           program considers to be enough to use. See Fast RAM.


Programmable
Also intelligent. Something that has the capability of being changed by means 
of a program.


Programmable logic array - PLA
See PLA.


Programmable sound generator - PSG
A sound synthesis chip capable of being programmed by a user, for instance the 
YM-2149 sound chip in the ST.


Programmable read-only memory - PROM
A read-only memory in which bit-patterns can be written by users using a 
'blower'. The term covers EPROMs and EEROMs. They are used in prototyping and 
in short-run production being more expensive than ROMs.


Programmer
A person with the skills to write, modify, document, test and possibly, design 
programs.


Programming language
A language suitable for writing computer programs. See Language.


Program name
The name given by the programmer to a program. Sometimes, the group of 
characters that uniquely identifies a particular program within storage. The 
two may not be the same. See File name.


Program specification
The description of a required program as produced by a systems analyst.


Program suite
A group of related programs contained within an application package.


Program support
The assistance a software supplier gives a user.


PROLOG
PROgramming in LOGic. A high-level language developed in France which is 
popular with those interested in artificial intelligence research.


PROM
Programmable Read-Only Memory.


PROM burner
A device used to program PROMs by selectively connecting a current to its 
pins.


Prompt
A message from the operating system or program to a user indicating its 
readiness as to input. In many command line interfaces it may simply be an 
indication of the current disk and/or directory and a cursor.


Propagation
The process of carrying signals between separated locations by means of 
electrical conduction, light or radio.


Propagation delay
The time that elapses between a change of logic level of an input and a 
resultant change in the output of a semiconductor device. This provides an 
indication of its access speed. ST RAM has a propagation time of 120 ns or 
less.


Proportional spacing
A typeface where each character has its own unique width. This is the normal 
typeface spacing used in books and magazines and most other professionally 
printed material. See Monospaced font.


Protected
Safeguards to prevent unauthorized access to computer storage, whether that is 
by a user to disk files or by a program to another program's memory.


Protocol
A set of rules or regulations, such as those for performing data interchanges 
between independent devices, for instance between two modems.


PRX
The file name extender for an inactive GEM program file. Such files are found 
in the AUTO folder where the presence of the .PRX extender makes the program 
unrecognizable to TOS and thus not loaded at boot-up.


PS
PostScript.


Pseudo static RAM
RAM devices that use the storage principles of dynamic RAM chips and the 
simple connections of static RAM chips.


PSG
Programmable Sound Generator. A sound synthesis chip that can be programmed by 
the user. See YM-2149.


PSRAM
Pseudo Static RAM.


PSS
Packet Switching Stream.


PSU
Power Supply Unit.


PTC1426
Atari 14 inch colour multisync monitor for the TT range. It has a .31 mm dot 
pitch and can connect to most PCs with its switchable PC VGA mode or TT medium 
resolution mode which enables it to show all TT resolutions except TT high 
resolution. The scan frequency of 70 Hz in VGA mode and 60 Hz in TT gives it a 
stable picture.


Public
Data, program variables or code that is available to any program or process 
that requires it.


Public domain
Freely available to all. It strictly refers to software where the copy 
restrictions have been relaxed by the author and for which a charge is waived 
and where the programmer has renounced all rights to the material. True public 
domain programs can be sold at a profit as they are owned by everyone 
(although this is generally discouraged) and can be freely altered. However, 
this is not generally the aim of most people who place programs into the 
public domain. The use of the term is confused and quite often the programmer 
will want to retain copyright. Under such circumstances, the program becomes 
either freeware or shareware. PD programs are common on the ST and provide a 
very rich and cheap source of programs, some of which are better than similar 
programs available commercially. They are generally distributed on bulletin 
board networks or other similar conferencing systems or by PD libraries which 
make a small administrative charge for their services, but not for the 
software. See Freeware, Shareware.


Pull-down menu
A menu in a GUI/WIMP environment activated from the top of the screen or 
window by clicking on its title. Pull-down menus are typical of the Macintosh 
environment, whereas TOS uses drop-down menus.


Pulse
A short-period presence of voltage or a voltage polarity change as used for 
timing or representation of data.


PUN_INFO
A data structure which provides the means for a hard disk driver to make the 
relationship between logical storage devices and the actual physical units.

  #define UNITS               16
  struct pun_info
  {
    int puns;                 /* no of physical hard drives  */
    char pun[UNITS];          /* table for logical drives    */
    long part_start[UNITS];   /* logical unit offset         */
    long cookie;              /* extended pun_info flag      */
    long *cookie_ptr;         /* pointer to cookie id        */
    unsigned version_num;     /* version of driver           */
    int max_sect_size;        /* largest logical sector size */
    long reserved[16];
  } PUN_INFO;

The new version is shown above. Sometimes only the first three members of the 
structure are used. Atari's AHDI v3 or later uses the whole structure. Hard 
disk drivers from ICD up to v6.5.5 do not fill in the part_start array 
correctly and only use the first three items.

puns contains the number of physical hard drive units. The pun and part_start 
arrays contain one element for each of the possible sixteen logical drives A: 
to P:. Element 0 is drive A:, element 1 is B: etc. In pun[], bits 0-2 of each 
byte give the ACSI address of the physical drive attached to the logical 
drive. Bit 7 is set if the logical drive is not an actual physical device (RAM 
disk or floppy drive B in a one floppy system). part_start[] contains the 
physical sector number of the first logical sector of each logical device.

If cookie is set to $41484449 ("AHDI") and cookie_ptr points to cookie the 
next part of the structure is valid. version_num contains the version number 
of the driver in the format $aabb which equals aa.bb. max_sect_size contains 
the size of the largest logical sector on any logical drive.


Purge
To remove a unit of data from storage.


Push
To add an item to the top of a stack.


Push-down stack
A data structure that provides for the addition and removal of items only at 
one end and in which all items move one item-space toward that end when an 
item is removed and away when an item is added. See LIFO.


Push-up list
A group of items to which items can be added at one end and removed from the 
other, a queue. See FIFO.


P
177 entries
EOF