1.iOS：
iOS 是由 Apple Incorporation 提供的移动操作系统。它主要是为 iPhone 和 iPod Touch 等苹果移动设备设计的。它早先被称为 iPhone 操作系统。它是一个基于Darwin(BSD) 操作系统的类Unix 操作系统。它是仅次于 Android 的全球第二大移动操作系统。它主要用 C、C++、Objective-C、汇编语言和 Swift 编写。 iOS 的第一个版本于 2007 年推出。
2. OpenVMS：
OpenVMS是由美国数字设备公司(DEC)开发的多用户多处理操作系统。它是一种基于虚拟内存的操作系统，设计用于分时、批处理和事务处理。它可用于许多平台，包括服务器和工作站。它是使用 BLISS、VAX Macro、C、Ada、PL/I、Fortran、UIL、Pascal、SDL、C++ 和 DCL 编写的。 OpenVMS 的第一个版本于 1977 年推出。该操作系统中使用的内核是带有模块的单体。
iOS 和 OpenVMS 的区别：
| S.No. | IOS | OPENVMS |
|---|---|---|
| 1. | It was developed by Apple Incorporation. | It was developed by Digital Equipment Corporation (DEC). |
| 2. | It was launched in 2007. | It was launched in 1977. |
| 3. | Its target system types are smartphone, music player and tablet computer. | Its target system types are server and workstation. |
| 4. | Computer architectures supported by iOS are ARMv8-A (iOS 7-present), ARMv7-A (iPhone OS 3-iOS 10) and ARMv6 (iPhone OS 1-iOS 4.2.1). | Computer architectures supported by OpenVMS are VAX, Alpha and IA-64. |
| 5. | Its kernel type is Hybrid. | Its kernel type is Monolithic with modules. |
| 6. | Its native APIs are Cocoa and BSD-POSIX. | Its native APIs are Proprietary. |
| 7. | It has the preferred license is Proprietary, APSL and GNU GPL. | It has the preferred license of Proprietary. |
| 8. | Its does not have package management. | Its package management is PCSI or VMSINSTAL. |
| 9. | The non-native APIs are not supported through its subsystems. | The non-native APIs supported through its subsystems are POSIX. |
| 10. | File systems supported by iOS are HFS+ and APFS. | File systems supported by OpenVMS are Files-11, ISO 9660, NFS and CIFS. |
| 11. | It has default GUI ‘on’. | It does not have default GUI ‘on’. |