利用信号量实现如下图所示的前趋图关系:答:Var a,b,c,d,e,f,g:semaphore:=0,0,0,0,0,0,0;begin parbegin begin S1;signal(a);signal(b);end;begin wait(a);s2; signal(c); signal(d); end;begin wait(b);s3; signal(e); end;begin wait(c);s4; signal(f); end;begin wait(d);s5; signal(g); end;b...