#include "stdio.h"
main()
{
int year,month,day,nyear,nmonth,nday;
int days,dayn1=0,dayn2,iyear,dayyear;
int i;
int monthtable[]={31,28,31,30,31,30,31,31,30,31,30,31};
printf("birthday=");
scanf("d% d% d%",&year,&month,&day);
if(year<=0||month<1||month>12||day<=0||day>31)
printf("data error\n");
printf("year,month,day is");
scanf("d% d% d%",&nyear,&nmonth,&nday);
if(nyear<=0||nmonth<1||nmonth>12||nday<=0||nday>31)
printf("data error");
iyear=year;
for(;iyear<=nyear-1;iyear++)
{if((iyear%4==0&&iyear%100!=0)||iyear%400==0)
dayyear=366;
else
dayyear=365;
dayn1=dayn1+dayyear;
}
if((nyear%4==0&&nyear%100!=0)||nyear%400==0)
monthtable[1]=29;

dayn2=nday;
for(i=1;i<nmonth;i++)
{dayn2=dayn2+monthtable[i-1];
days=dayn1+dayn2;
}
printf("days isd%",days);
getch();
}
上面是小妹写的程序，但是在WIN-TC上能编译，但是只要运行第一个输入后，不经过运算，原样输出printf后的语句（不计算），不知怎搞的，望指教，么么。。

楼主的程序还没写完呢！～
#include "stdio.h"
main()
{
int year,month,day,nyear,nmonth,nday;
int days,dayn1=0,dayn2,iyear,dayyear;
int i;
int monthtable[]={31,28,31,30,31,30,31,31,30,31,30,31};
printf("birthday=year/month/day");
scanf("%d/%d/%d",&year,&month,&day); /*输入格式错误*/
if(year<=0||month<1||month>12||day<=0||day>31)
printf("data error\n");
printf("year/month/day is");
scanf("%d/%d/%d",&nyear,&nmonth,&nday); /*同上，输入格式错误*/
if(nyear<=0||nmonth<1||nmonth>12||nday<=0||nday>31)
printf("data error\n");
iyear=year;
for(;iyear<=nyear-1;iyear++)
{
if((iyear%4==0&&iyear%100!=0)||iyear%400==0)
dayyear=366;
else
dayyear=365;
dayn1=dayn1+dayyear;
}
if((nyear%4==0&&nyear%100!=0)||nyear%400==0)
monthtable[1]=29;
dayn2=nday;
for(i=1;i<nmonth;i++)
{
dayn2=dayn2+monthtable[i-1];
/* days=dayn1+dayn2; days为什么循环啊？*/
}
days=dayn1+dayn2;
printf("days is%d",days); /*输出格式错误*/
}

你的程序改了下，没写完的部分自己去补！～

我实在找不出错在什么地方了，得出的总是负数～～～～

#include <stdio.h>
main()
{
long year,month,day,nyear,nmonth,nday;
long days=0,iyear,imonth,iday;
int i;
int monthtable[]={31,28,31,30,31,30,31,31,30,31,30,31};

printf("Begin:year month day="); /*输入起始日期*/
scanf("d% d% d%\n",&year,&month,&day);

if((year<=0)&&(month<1)&&(month>12)&&(day<=0)&&(day>31)) /*判断输入是否正确*/
{
printf("data error\n");
exit(1); /*输入错误数据退出*/
}
printf(" END :year month day="); /*输入中止日期*/
scanf("%d %d %d\n",&nyear,&nmonth,&nday);

if((nyear<=0)&&(nmonth<1)&&(nmonth>12)&&(nday<=0)&&(nday>31)) /*判断*/
{
printf("data error");
exit(1);
}

iyear=year; /*从起始年到中止年间天数*/
for(;iyear<nyear;iyear++)
{
if((iyear%4==0)&&(iyear%100!=0)||(iyear%400==0))
days+=366; /*闰年*/
else
days+=356;
}

imonth=month;
if(((year%4==0)&&(year%100!=0))||(year%400==0)) /*加入从起始日期的下个月到年终天数*/
monthtable[1]=29;
for(++imonth;imonth<=12;imonth++)
days+=monthtable[imonth-1];

iday=day; /*为美观规范设立iday*/
days+=monthtable[month-1]-iday; /*加入起始日期当月剩余天数*/

if(((nyear%4==0)&&(nyear%100!=0))||(nyear%400==0)) /*判断中止日期当年是否为闰年*/
monthtable[1]=29;

for(i=1;i<nmonth;i++) /*加入终止日期当年到终止日期月份的天数*/
days+=monthtable[i-1];

days+=nday; /*加入终止日期当月天数*/

printf("days is=%d",days);

getch();
}

/*很多%d都写成了d%*/

当前日期可以通过函数调用得到。
struct date date1;
getdate(&date1); /*dos.h中*/

备注：
date的成员为：
struct date {
int da_year;
char da_day; /* Day of the month */
char da_mon; /* Month (1 = Jan) */
};

至于算法嘛？？乱七八糟！！

只考虑到当前的年月日都大于出生的年月日 没有考虑到当前的年份大于出生年份时 当前的月日小于出生的月日