After it has been installed, the DOS, as it is called (once identified, nothing in computerese is ever called by its full name  a Personal Computer becomes a PC; a Disk Operating System becomes a DOS; if it is made by a company called MicroSoft, it is called MS/DOS), performs certain functions, though rarely any that anyone but a computer specialist would want to perform.
( ( After ( it ( has ( been installed ) ) ) ) ( , ( ( ( ( ( the DOS ) , ) ( as ( it ( is ( called ( -LRB- ( ( once ( ( ( ( ( identified ( , ( ( nothing ( in computerese ) ) ( ( is ever ) ( called ( by ( ( its ( full name ) ) ( ( a ( Personal Computer ) ) ( becomes ( a PC ) ) ) ) ) ) ) ) ) ) ; ) ( ( a ( Disk ( Operating System ) ) ) ( becomes ( a DOS ) ) ) ) ; ) ( ( if ( it ( is ( made ( by ( ( a company ) ( called MicroSoft ) ) ) ) ) ) ) ( , ( it ( is ( called MS/DOS ) ) ) ) ) ) ) -RRB- ) ) ) ) ) ) ) , ) ( ( ( ( performs ( certain functions ) ) , ) ( though ( rarely ( ( any ( ( ( that anyone ) but ) ( a ( computer specialist ) ) ) ) ( would ( want ( to perform ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN After) (S (NP (PRP it)) (VP (VBZ has) (VP (VBN been) (VP (VBN installed)))))) (, ,) (NP (NP (DT the) (NNP DOS)) (, ,) (SBAR (IN as) (S (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (PRN (-LRB- -LRB-) (SBAR (IN once) (S (S (S (VP (VBN identified))) (, ,) (NP (NP (NN nothing)) (PP (IN in) (NP (NN computerese)))) (VP (VBZ is) (ADVP (RB ever)) (VP (VBN called) (PP (IN by) (NP (NP (PRP$ its) (JJ full) (NN name)) (SBAR (S (NP (DT a) (NNP Personal) (NNP Computer)) (VP (VBZ becomes) (NP (DT a) (NN PC)))))))))) (: ;) (S (NP (DT a) (NN Disk) (VBG Operating) (NN System)) (VP (VBZ becomes) (NP (DT a) (NNP DOS)))) (: ;) (S (SBAR (IN if) (S (NP (PRP it)) (VP (VBZ is) (VP (VBN made) (PP (IN by) (NP (NP (DT a) (NN company)) (VP (VBN called) (NP (NNP MicroSoft))))))))) (, ,) (NP (PRP it)) (VP (VBZ is) (VP (VBN called) (NP (NNS MS/DOS))))))) (-RRB- -RRB-)))))) (, ,)) (VP (VBZ performs) (NP (JJ certain) (NNS functions)) (, ,) (SBAR (IN though) (S (ADVP (RB rarely)) (NP (DT any) (NP (DT that) (NN anyone)) (CC but) (NP (DT a) (NN computer) (NN specialist))) (VP (MD would) (VP (VB want) (S (VP (TO to) (VP (VB perform))))))))) (. .)))
Nothing in computer sense is called by its full name.
( ( Nothing ( in ( computer sense ) ) ) ( ( is ( called ( by ( its ( full name ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NN Nothing)) (PP (IN in) (NP (NN computer) (NN sense)))) (VP (VBZ is) (VP (VBN called) (PP (IN by) (NP (PRP$ its) (JJ full) (NN name))))) (. .)))