刚刚开始认识C,为什么每当输入数字时，command window 会自动关闭。我用Dev、C++开始学习的。

谢谢回复，随心。。。这么快， 出乎意料。
我刚学了2天，我会继续坚持。。。

/* change.c */
#include <stdio.h>


int main()
{
      int amount, twenties, tens, fives, ones, r20, r10;
      printf("Enter the amount of change needed:");
      scanf("%d", &amount);
      twenties = amount/20;    //number of 20s notes
      r20 = amount % 20;         //number of remainder after 20s
      tens = r20/10;           //numer of 10s notes
      r10 = r20 % 10;           //number of remainder after 10s
      fives = r10/5;           //number of 5s notes
      ones =  r10 % 5;          //number of 1s notes
      putchar('\n');a
      printf("To make change for $%d give the following:\n", amount);
      printf("%d twenties\n", twenties);
      printf("%d tens \n", tens);
      printf("%d fives \n", fives);
      printf("%d ones \n", ones);
      return 0;
      }

随心，添加了头文件和 系统暂停语句后，这2天所有的练习的东西都开始工作，我继续努力去了。。。很感谢！！！

/* Salary accounting.c */
#include <stdio.h>
#include <stdlib.h>

int main()
{
    char name[10], period[20];
    int id [4];
    float salary, tax_rate, tyott_vak, net_salary, net_payment;
   
    printf("Employee Name:");
    gets(name);
    printf("Payment period:");
    gets(period);   
    printf("Emplyee ID:");
    scanf("%d", id);
    printf("Monthly Salary is: ", salary);
    scanf("%f", &salary);
    printf("%s Tax rate is: ", tax_rate);
    scanf("%f", &tax_rate);
    net_salary = salary - (salary*tax_rate) - (salary*tyott_vak);
    printf("Vakuutus is:",tyott_vak);
    scanf("%f", &tyott_vak);
   
    puts("\n\n\n\n\n");
    puts("           SALARY ACCOUNTING");
    printf("%s\n %s\n", name, period);
    printf("\t\t\t\t\t %-10s\t %10.2f\n", "Monthly Salary", salary);
    printf("\t\t\t\t\t %-10s\t %10.2f\n" "Tax rate", tax_rate);
    printf("\t\t\t\t\t %-10s\t %10.2f\n", "Vakuutus rate", tyott_vak);
    printf("\t\t\t\t\t %-10s\t %6.2f", net_salary);
    system("pause");
    return 0;  
   
   
    }

解决好了，变量名搞错了。