›This is version 1.2 of Ralph Walden's slightly buggy implementation of ARCX for›the Atari 8-bit series of computers.  The program follows the instructions.››You thought there was intelligent life...              fireplace@cup.portal.com›                                            sun!portal!cup.portal.com!fireplace››~~YOUR TERMINAL DOES NOT SUPPORT HOLOGRAPHIC IMAGES - GRAPHICS SKIPPED~~››-------------------------------------------------------------------------------›     An ARC'd file contains one or more files which has been compressed into a›single file.  This reduces the size by an average of 30-50%.  ARCX.COM is then›needed to extract the files from the ".ARC" file.  ".ARC" files maintain a CRC›check to make certain the file is intact - if ARCX tells you the CRC check was›wrong, then the ".ARC" file you are trying to extract from is bad.  This adds›another check to program validity for files downloaded using XMODEM.››     Before running ARCX be sure you have removed all cartridges and BASIC is›off (48K is a requirement).  Now load ARCX.COM from DOS, or type ARCX if you›are using Sparta or an OSS DOS.  ARCX will then ask you for the name of the›".ARC" file to extract files from.  If you don't remember the name, you can›get a directory by pressing the '+' key.  After entering the name of the ".ARC"›file, ARCX will ask you for the drive to send the extracted files to.  Next,›ARCX will ask you if you want the screen turned off.  If you press 'Y', then›the screen will be turned off during the extraction process which will speed›up the process about 20%.  ARCX will extract all files from the ".ARC" file and›write it to the destination drive.  IMPORTANT - ARCX creates files using the›filenames contained in the ".ARC" file.  When you download an ".ARC" file from›a BBS, you should be sure to give it the extension ".ARC".  Otherwise, you›might have a name conflict between the ".ARC" file, and the file it is trying›to extract.  It's a good idea to extract an ".ARC" file to a blank disk so you›know there won't be any files overwritten.››     The algorithms used for extracting ".ARC" files are quite complex, and›therefore rather slow.  A rough estimate is 1 minute for each 5K of source›file.  ARCX uses all available memory and buffers the input and output so your›disk drives won't be running all the time.  It's not unusual for the disk›drives to remain inactive for over a minute while ARCX works on the ".ARC"›file.››     Keep in mind that the extracted files can be more then twice the size of›the original ".ARC" file.  Be sure you have enough room before you start!››     ARCX will work with virtually any DOS except Smart DOS.››     ARC was originally written in C by Tom Henderson of System Enhancement›Associates.  The source code was placed in the public domain allowing for ARC›and ARCX to be ported to a wide variety of computers (it was written in C,›hence its ability to be ported to other computers).  ARCX as implemented in›the 8 bit version will support all ".ARC" files created with version 5 of ARC.›There are a few limitations.  ARCX will not supported ".ARC" files encoded with›a password; it will not support a single source file within the ".ARC" file›that exceeds 64K; and it will not support "crunched" files created with a›pre-version 5 ARC program.  It is extremely unlikely that you would encounter›any of these limitations.››     When ARC (not ARCX) compresses a file(s), it tries out 4 different›methods of compression, and selects whichever method yields the smallest file.›These methods are referred to as stored, packed, squeezed, and crunched.  The›method used will be transparent to the user of ARCX which will extract files›stored in any of these formats.  For the curious, stored is as is, i.e., the›file was to small to be worth compressing.  Packed is used when a file has a›large number of repeating bytes.  Squeezed is the Hufman method, commonly used›on large binary files.  Crunched is the Lempel-Zev method and is the most›commonly used as it gives the best results.  At this time, there is no better›compression method known.  Though an 8-bit ARC.COM is in the works, it will›only created stored, packed, or squeezed files.  The "crunched" routine›requires a 25K continuous table, plus additional buffers for over 30K of buffer›space, and therefore can not be implemented on the 8-bit Atari.  Currently›8-bit files can be ARC'd on the ST, a PC compatable, or any computer with›version 5 (or later) of ARC.››     For the advanced user:  ARCX.COM 1.1 (or later version) will accept›paramters on a command line if you are using Sparta DOS or DOS XL.  The format›is:››ARCX filename drive# filename drive# etc.››The filename is the ".ARC" filename.  You do not need to include the extension›if it is ".ARC" (which it should be).  If the ".ARC" file is on the default›drive, then you do not need to enter the drive specification.  Follow the›filename with a space and the drive number to send the files to.  The screen›will be turned off and ARCX will extract the files without further input from›you.  You may have as many filenames and drive#'s as will fit on a 64 byte›command line.››-Ralph Walden, SYSOP, ACE BBS›(503) 343-4352, 300/1200/2400 baud, 24 hours›