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二) 
2.1 
#include<iostream.h>voidmain() 
{//本题原考虑在16位机器上实验目前多为32位机器,故已过时。inta=42486; 
cout<<oct<<a<<endl 
<<hex<<a<<endl;unsignedb=42486; 
cout<<dec<<(signed)b<<endl;} 
2.2 
#include<iostream.h>#include<iomanip.h> 
constdoublepi=3.1415926;voidmain(){ 
doubleradius1,radius2; 
cout<<"pleaseinputtwonumbers:\n";cin>>radius1>>radius2; 
cout<<setw(10)<<pi<<setw(10)<<radius1 
<<setw(10)<<(pi*radius1*radius1)<<endl<<setw(10)<<pi<<setw(10)<<radius2 
<<setw(10)<<(pi*radius2*radius2)<<endl; 
} 
2.3 
#include<iostream.h>#include<iomanip.h> 
constdoublee=2.718281828;voidmain(){ 
cout<<setprecision(10)<<e<<endl 
<<setiosflags(ios::fixed)<<setprecision(8)<<e<<endl<<setiosflags(ios::scientific)<<e<<endl; 
} 
2.4 
#include<iostream.h> 
 
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