1. iOS：
iOS是苹果公司提供的移动操作系统。它主要是为iPhone和iPod Touch等Apple移动设备设计的。它以前被称为iPhone OS。它是基于Darwin(BSD)操作系统的类Unix操作系统。它是仅次于Android的世界第二使用最多的移动操作系统。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年发布。
2. OpenVMS：
OpenVMS是由Digital Equipment Corporation(DEC)开发的多用户和多处理操作系统。它是基于虚拟内存的操作系统，旨在用于分时，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年发布。此操作系统中使用的内核与模块是整体的。
iOS和OpenVMS之间的区别：
| 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’. |