Mac OS 7 was a major change from the earlier System Software, introducing integrated multitasking, a revamped desktop, networking, and transitioning the name from 'Macintosh System Software' To 'MacOS'. It was followed by by MacOS 8.x.
Running Mac OS 7.x requires a Motorola 68000 based Macintosh, a supported model of Power PC based Macintosh (7.1 or later) or one of the following emulators:

Version 5.0.4 of the Apple CD-ROM extension should only be used by DOS Compatibility Card owners having trouble mounting CDs on the DOS side. Download Information. Update Mac OS 8.5 or 8.5. Mac OS 9 is the ninth and last major release of Apple's classic Mac OS operating system.Introduced on October 23, 1999, it was promoted by Apple as 'The Best Internet Operating System Ever', highlighting Sherlock 2's Internet search capabilities, integration with Apple's free online services known as iTools and improved Open Transport networking. While Mac OS 9 lacks protected memory and full.
Mini vMac - Runs MacOS 1.1-7.5.5, emulates a black and white Motorola 68K based Mac Plus
What is All Macintosh Roms (68K + PPC)? This is an archive containing all of the most popular Macintosh models ROM files for emulation purposes, ranging from the first 64K ROM from the Mac 128K to the 4MB ROM files from the Bandai Pippin or PowerMac G3, listed below in ROM size, then by release date from oldest to newest.

Basilisk II - Runs MacOS 7.x-8.1, emulates later color Motorola 68k based Macs.
SheepShaver - Runs MacOS 7.5.2-9.0.4, emulates a Power PC based Macintosh.
Screenshots


Release notes
An interim catchup release in the wake of Windows 95, bundling some extra desk accessories, more hardware support, and new APIs such as the modernized Open Transport.
Installation instructions
Note: Some of these CD images are actually hard disk volumes. You can mount those in an emulator, or some older CD burning programs know how to write them as a CD/ISO.
Mac Os 8.1 Download
7.5.5 is the last supported version on Mac Plus, XL, Mac II, IIx, LC, IIcx, and SE/30, or anything with less than 68030 and 32-bit clean ROM.
