C++

#include<iostream>#include<cmath>using namespace std;int main(int argc,char *argv[]){float a,b,c,disc;cout<<"Please input a,b,c:";cin>>a>>b>>c;if(a == 0)cerr<<"a is equal to zero,error!"<<endl;elseif((disc = b*b - 4 * a * c) < 0)cerr<<"disc = b * b - 4 * a *c < 0"<<endl;else{cout<<"x1 = "<<( - b + sqrt(disc))/(2 * a)<<endl;cout<<"x2 = "<<( - b - sqrt(disc))/(2 * a)<<endl;}return 0;}

#include<iostream>using namespace std;int main(){char *a = "BASIC";for(int i = 4; i >= 0; i--)cout.put(*(a + i));cout.put('\n');return 0;}

#include<iostream>#include<fstream>using namespace std;int main(int argc,char *argv[]){int a[10];ofstream outfile("f1.txt",ios::out);if(!outfile){cerr<<"open error"<<endl;exit(1);}cout<<"enter 10 interger numbers:"<<endl;for(int i = 0;i < 10; i++){cin>>a[i];outfile<<a[i]<<" ";}outfile.close();return 0;}