z/OS is a 64-bit operating system for IBM z/Architecturemainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions. Like OS/390, z/OS combines several formerly separate, related products, some of which are still optional. z/OS has the attributes of modern operating systems but also retains much of the older functionality that originated in the 1960s and is still in regular use—z/OS is designed for backward compatibility.
z/OS is a 64-bit operating system for IBM z/Architecture mainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions. Like OS/390, z/OS combines several formerly separate, related products, some of which are still optional. z/OS has the attributes of modern operating systems but also retains much of the older functionality that originated in the 1960s and is still in regular use—z/OS is designed for backward compatibility.
z/OS supports stable mainframe facilities such as CICS, COBOL, IMS, PL/I, IBM Db2, RACF, SNA, IBM MQ, record-oriented data access methods, REXX, CLIST, SMP/E, JCL, TSO/E, and ISPF, among others. However, z/OS also implements 64-bit Java, C, C++, and UNIX (Single UNIX Specification) APIs and applications through UNIX System Services – The Open Group certifies z/OS as a compliant UNIX operating system – with UNIX/Linux-style hierarchical HFS and zFS file systems. These compatibilities make z/OS capable of running a range of commercial and open source software. z/OS can communicate directly via TCP/IP, including IPv6, and includes standard HTTP servers (one from Lotus, the other Apache-derived) along with other common services such as SSH, FTP, NFS, and CIFS/SMB. z/OS is designed for high quality of service (QoS), even within a single operating system instance, and has built-in Parallel Sysplex clustering capability.