variants linux bsd popular areas four operating systems certified open group holder unix trademark unix hp 's hp ux ibm 's aix descendants original system v unix designed run respective vendor 's hardware contrast sun microsystems 's solaris run multiple types hardware including x sparc servers pcs apple 's macos replacement apple 's earlier non unix mac os hybrid kernel based bsd variant derived nextstep mach freebsd unix interoperability sought establishing
Formal science Computer science Operating systems