CentralNotice Microsoft POSIX subsystem From Wikipedia, the free encyclopedia Jump to: navigation , search Microsoft POSIX subsystem is one of 3 subsystems of several operating systems from the Windows NT family (together with OS/2 and Windows subsystems). Microsoft Windows implements only the first version of the POSIX standards , namely POSIX.1. The official code of POSIX.1 is ISO/IEC 9945-1:1990 or IEEE standard 1003.1-1990. The subsystem was included because of 1980s US federal government 's requirements listed in Federal Information Processing Standard (FIPS) 151-2. [ 1 ] Versions Windows NT 3.5 , Windows NT 3.51 and Windows NT 4 were certified as compliant with the FIPS 151-2. The runtime environment of the subsystem is provided by two files: psxss.exe and psxdll.dll . A POSIX application uses psxdll.dll to communicate with the subsystem while communicating with...