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Z/Archive Overview

[Z/ARCHIVE SYSTEM]

The Z/Archive System

What is the Z/Archive System?

The Z/Archive System is a set of programs used to:

  • Compress and expand individual files.
  • Create self-extracting compressed archives.
  • View compressed and archived files.

The following programs are components of the Z/Archive System:

  • ZCMP - Compresses individual files.
  • ZEXP - Expands a file compressed with ZCMP.
  • ZARC - Creates self-extracting archives.
  • ZDARC - Extracts files from an archive.
  • ZVIEW - Views compressed or archived files.

Archives created with Z/Archive are self-extracting. This means the files in the archive can be extracted by executing the archive file itself.

If memory is limited, ZDARC can be used to extract the files from an archive that is too large to be loaded and executed. ZDARC can also be used to extract a single file from a multi-file archive.

The Z/Archive file viewer, ZVIEW can view text files compressed with ZCMP or archived with ZARC. "Normal" text files created with VUE or a similar editor can also be viewed. In addition, ZVIEW accepts wildcard file specifications and can view several files sequentially.

Is Z/Archive hard to use?

Absolutely not. Following are some examples of common Z/Archive functions. "[RET]" indicates the RETURN or ENTER key.

Archive a set of files:

ZARC ARCHIV = *.BAS[RET]

Extract the files in an archive:

ARCHIV[RET] or ZDARC ARCHIV.LIT[RET]

List the files in an archive:

ARCHIV/C[RET] or ZDARC ARCHIV.LIT/C[RET]

Compress one file:

ZCMP FILE.TXT[RET]

Expand a compressed file:

ZEXP FILE.CMP[RET]

View a compressed file:

ZVIEW FILE.CMP[RET]

What kind of compression will I get?

The level of compression achieved by Z/Archive depends primarily on the content of the file. Files that contain repeated patterns of byte values, such as words, sequences of nulls or spaces, commands, or similar data will compress more than files with more random content, such as program files.

List files are often very compressible. In one test documentation from the November 1993 AlphaCD totaling more than 4400 blocks was archived into a Z/Archive file of only 718 blocks, a reduction of 84%!

Executable program files, such as ".LIT" files, are usually not as compressible. To determine an average ratio for LIT files we used Z/arc to archive all of the LIT files on the. A total of 17726 blocks of LIT files were archived into a 9479 block file-an average reduction of about 47% per file.

Program source files are usually good candidates for compression. For example, ZCMP compressed several large AlphaBASIC source files from a point of sale application an average of 78%. The 172 block BASIC source file DIALR5.BAS, distributed with VersiCOMM-Plus, can be compressed nearly 80%. It has been our experience that AlphaBASIC files will usually compress about 70%-75% and M68 assembly language source files about 65%-75%. For example, the file IDV681.M68, distributed with AMOS, compresses 75%.

Data files can be very compressible. In a test run on an actual business system, ZCMP compressed a 19 .2 Mb Sales History file over 85%. (This file was the data file component of an ISAM file.)

Download the ZCMPX compression simulator (Z/Archive self-extracting file) and find out how much Z/Archive would compress files on your system. ZCMPX calculates how much an individual file would be compressed using the Z/Archive compressor, ZCMP.

Are there special features I should know about?

Command Embedding

A unique and very useful feature of the Z/Archive system is its capability to embed a command in the archive and then execute it when expansion of the archive is complete. For example, if the command "VUE README.DOC" is embedded in an archive, along with the file README.DOC, when expansion of the archive is complete the user will be left VUEing the file README.DOC. Using this feature the archive could TYPE a message, execute an installation command file, or even chain to another self-extracting file!

Restoration Options

Z/Archive's default mode of operation is to restore all of the files in the archive to the account in which the archive is executed, regardless of the file's original account and device. If desired, at the time the archive is expanded, you can specify a switch that results in the files in the archive being restored to their original accounts and devices. You can also specify a substitute device to use when restoring the archive's files. So, for example, you could specify that all files in the archive should be restored to DSK0: instead of the device recorded in the archive.

You can also specify a substitute device when the archive is created. So, for instance, if the files you were archiving resided on DSK25: you could substitute DSK0: for DSK25: in the archive. If the archive is then restored to its original accounts, it will be restored to DSK0:.

CRC File Validation

When a file is compressed using Z/Archive a CRC checksum is calculated for the contents of the uncompressed file and stored in the compressed file. When the file is expanded the CRC is checked for validity.

Is Z/Archive compatible with 2.2 systems and extended directories?

Z/Archive requires AMOS 1.3D or 1.0D or later. It is compatible with AMOS 2.2x and can be used on systems with extended directories. Z/Archive requires 250K of free memory for compressing files.

Is there a version that will run on my PC?

A PC version of Z/Archive is in the works. The PC versions of the individual file compression and expansion programs, ZCMP and ZEXP, have been completed and are available on a special order basis. Contact us for more information.

What does it cost?

The suggested retail price for the Z/Archive System is US$ 249.00. For more information or to place an order call Valley Programming Service at 818-992-5134.

Z/Archive Selected For Use By Alpha Micro Technical Support

Alpha Micro Technical Support now uses Z/Archive to create self-extracting patch files. Better compression, improved compatibility with AMOS systems, and more flexibility in creating and restoring archives were some of the reasons given for using the product.

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