Why did they make an ISO if there is a ZIP?

Question

ISO

Why did they make such a data format as "Disk Image", if there are archiving methods?
ISO is essentially zip without compression, and ISZ is just compressed. And DMG is also essentially an archive.
The only difference that I saw between these formats is that you can mount "disk images" and immediately run data from them (although I have never tried it with ISZ) and then, in the case of DMG, you need to wait a bit (if a weak computer or large archive) while the data is unzipped.
So in the same way, mounting and instant copying from uncompressed ZIP archives could be done.

Answer 1

.iso files are an informal term for an optical disc image that originally allowed the ISO9660 file system, also known as CDFS (Compact Disc File System) to be fully stored as a file.
In a general sense, it allows you to store not only ISO9660, but also another optical disc format: UDF (ISO / IEC 13346), as well as ISO9660 format extensions: Joilet, Rock Ridge, El Torito, Apple ISO9660 Extension.
The soot standard ISO9660 was adopted in 1988 and describes a universal file system for storing information on digital media for compatibility between popular operating systems (Unix, Mac OS, Windows, etc.), as well as a huge number of electronic devices that can read information from digital media (video, audio players, game consoles, CD players, ...).
In addition to the data itself and the encoding method, information about the publisher, the volume (disk) identifier, as well as the date of creation and the expiration date of the disk could be placed on the disk.
Separately, an area was allocated for creating a boot sector (OS installer loader, etc.).
Since the life of the disk was limited, and the media could be physically damaged, the problem of transferring data from digital media to another media with the preservation of all information became actual over time.
This task could be solved in the simplest version "on the forehead" - copying all the data from the disk to a computer, and then writing it to another digital disk, but this method could not be universal, since it was not suitable for all data formats.
The exception was disks that stored important service (boot area) or license information (license keys, copy protection systems) in the service sectors of the disk.
Creating a full-fledged copy from one medium to another medium on the fly was not suitable for everyone (since it was required to have 2 devices, one of which allowed writing information, and the other was used for reading), as well as some programs for burning discs at that time did not (technically or legally) support the creation of a 1 to 1 copy, then over time software appeared, the task of which was to be able to make a "mirror" copy of the disk and write it as a special file (so that all service information was not lost) to the local a computer.
Thus, the very first disc image formats (.iso, .img) appeared, or proprietary .mdf (Alcohol 120%), .nrg (Nero), .uif (MagicISO), which at the very beginning of their appearance solved the problem of copying service information and used as a buffer format when cloning discs using 1 burner.
But even in this form, discs were still more common than .iso files, as they were the main way to transfer information in places where the Internet was not yet available. (Although there were people who used hard drives as an alternative way to transfer data).
The .iso files themselves were not initially so useful, since there were no CD / DVD emulators that would be integrated into the file system, or they cost money and had their own proprietary formats, and ISO9660 support was partially implemented or not. supported all the possibilities of the format.
Only with the increase in the size of hard drives and the speed of the Internet, as well as the emergence of full-fledged emulators of .iso files, the time has come when people began to abandon digital disks and store information on other media.
But since various information stored at that time on digital media required either labor costs for conversion (CD-Audio, DVD-Auido, video discs) or emulation of the presence of a licensed disc in the drive (games, specialized software),
then most people began to duplicate information from digital media into * .iso files, as this was the easiest solution to their problems.
Therefore, at the time *.iso files appeared, they made it possible to solve problems that were relevant at that time (buffer file, emulation of specialized disks).
Now *.iso files are mainly used only in cases where other methods cannot fully help in solving the task.
As an alternative to optical discs, the Internet and flash memory had come by that time.
To replace ISO9660, the UDF file system appeared in 1995, which was able to solve ISO9660 problems such as writing files over 4GB, as well as overwriting data on digital media (etc.).
ZIP archives are already an information compression format that is not suitable for all types of information (audio, video, graphics are poorly compressed by ZIP algorithms, so other compression algorithms are used for multimedia).
In addition, the presence of an archive requires the presence of a dearchiver on the device, which is very difficult for embedded technology in which this functionality will lead to an increase in the cost of the product and the use of more expensive electronic components) without a significant gain in something else.
ISZ - (aka ISO Zipped) is already a specialized format, which is compressed by ISO9660 using zlib or bzip2. It was mainly used by enthusiasts to save some disk space where *.iso was not expected to be used frequently, and at the same time they were ready for inconveniences when working with this format in the future (unpacking time, availability of special programs).
DMG is a platform-specific format for storing disk images for the Mac OS operating system.
In addition to the features that ISO 9660 gave, it also had the ability to encrypt information using compression, and the ability to store Mac OS-specific metadata about files was also implemented.
Now this format is mainly used as a means of distributing software archives using the Internet.
In addition, this format is "hybrid" and supports the ability to store multiple file systems (including ISO9660) within a single *.dmg file.