What is the {portable computer} for {operating system} of {MS-DOS}
MS-DOS was the operating system for which portable computer?
What portable computer had MS-DOS as the operating system?
SELECT DISTINCT ?p WHERE { ?p rdf:type ontology:portable_computer . ?p property:operating_system resource:MS-DOS }
select distinct ?subj where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?subj . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P306> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q47604> . ?subj <http://www.wikidata.org/entity/P31> <http://wikidata.dbpedia.org/resource/Q1820120> } 
 select distinct ?sbj where { ?sbj wdt:P306 wd:Q47604 . ?sbj wdt:P31 wd:Q1820120 } 
Zenith Z-171