#include<stdio.h>
void main()
{   
    int m;
    scanf("%d",&m);
    if(m=0)
        {
        printf("请输入一个十进制的数a=");
        float a,b,c=60,d,f=60,g;
        scanf("%f",&a);
        b=(int)(a);
        c*=a-b;
        d=(int)c;
        f*=c-d;
        printf("%.0f\'%.0f\'%.0f\"\n",b,d,f);
        g=b+d/100+f/10000;
        printf("%.4f\n",g);
        }
    else if
        {
        printf("请输入一个度数a=");
        float a,b,c,d=60,f=3600,g;
        scanf("%f",&a);
        b=(int)a;
        a=(a-b)*100;
        c=(int)a;
        a=(a-c)*100;
        d=c/60;
        f=a/3600;
        g=b+d+f;
        printf("g=%.4f\n",g);
        }
}   

error C2143: syntax error : missing ';' before 'type'
E:\text\2.c(10) : error C2065: 'a' : undeclared identifier
E:\text\2.c(11) : error C2065: 'b' : undeclared identifier
E:\text\2.c(12) : error C2065: 'c' : undeclared identifier
E:\text\2.c(13) : error C2065: 'd' : undeclared identifier
E:\text\2.c(14) : error C2065: 'f' : undeclared identifier
E:\text\2.c(16) : error C2065: 'g' : undeclared identifier
E:\text\2.c(20) : error C2059: syntax error : '{'
E:\text\2.c(22) : error C2143: syntax error : missing ';' before 'type'
E:\text\2.c(33) : error C2059: syntax error : '}'
执行 cl.exe 时出错.

2.exe - 1 error(s), 0 warning(s)

c*=a-b 为c=c*a-b,没有错。另外  ，变量需要定义两次，没法放在开头。但这个程序总存在一个错误 E:\text\2.c(10) : error C2143: syntax error : missing ';' before 'type'（在C语言）；在cpp中，错误为
E:\text\Cpp1.cpp(11) : warning C4244: '=' : conversion from 'int' to 'float', possible loss of data；
请解答

正解！都能实现。朋友又给了两个相似的：
       #include<stdio.h>
       void main()
      {
        int m;
        printf("十进制数转换到度分秒形式数请输入1，反之输入2\n");
        scanf("%d",&m);
       switch (m)
       case 1:
      {
       {
        printf("请输入一个十进制的数a=");
        float a,b,c=60,d,f=60,g;
        scanf("%f",&a);/*输入任意实数*/
       b=(int)a;
       c*=a-b;
       d=(int)c;
       f*=c-d;
       printf("%.0f\'%.0f\'%.0f\"\n",b,d,f);
       g=b+d/100+f/10000;
        printf("%.4f\n",g);break;
        }
       case 2:
      {
       printf("请输入一个度数a=");
      float a,b,c,d=60,f=3600,g;
      scanf("%f",&a);
       b=(int)a;
        a=(a-b)*100;
        c=(int)a;
      a=(a-c)*100;
         d=c/60;
        f=a/3600;
       g=b+d+f;
        printf("g=%.4f\n",g);
       }
     }
——————————————————————————————————————————————————————————————————————————
         #include<stdio.h>
         main()
        {
          int t;
          printf("十进制数转换到度分秒形式t=1，度分秒转化为十进制t=2\n");
          scanf("%d",&t);
         if (t==1)
       {
         printf("请输入一个十进制的数a=");
        float a,b,c=60,d,f=60,g;
        scanf("%f",&a);
        b=(int)a;
        c*=a-b;
        d=(int)c;
        f*=c-d;
        printf("%.0f\'%.0f\'%.0f\"\n",b,d,f);
        g=b+d/100+f/10000;
        printf("%.4f\n",g);
 }
 else if(t==2)
 {
     printf("请输入一个度数a=");
        float a,b,c,d=60,f=3600,g;
        scanf("%f",&a);
        b=(int)a;
        a=(a-b)*100;
        c=(int)a;
        a=(a-c)*100;
  d=c/60;
  f=a/3600;
  g=b+d+f;
  printf("g=%.4f\n",g);
 }
}
           在此，感谢大家的帮助！！！