一选择题
4.1 B
4.2 B
4.3 A
4.4 D
4.5 D
4.6 A
4.7 B
4.8 C
4.9 D
4.10 C
二填空题
4.11 1,0
4.12 (<,<=,>,>=)优先于(!=,==)
4.13 ! && ||
4.14 !,<,<=,>,>=,!=,==,&&,||
4.15 !
4.16 (a==b)||(a<c),(x<-4)&&(x>4)
4.17 1
4.18 x<=0 x!=0
4.19 3 2 2
4.20 *#
三编程题
4.21
switch(int(a/10)){
 case 0:
 case 1:
 case 2: m=1;break;
 case 3: m=2;break;
 case 4: m=3;break;
 case 5: m=4;break;
 default : m=5;
}
4.22
#include "stdio.h"

void main()
{
  int y0,y1,m0,m1,d0,d1;
  scanf("%d%d%d%d%d%d",&y0,&m0,&d0,&y1,&m1,&d1);

  if (d1<d0) {
      if (m1-1<m0) printf("%d,%d,%d\n",y1-y0-1,12-(m0-m1),30-(d0-d1));
 else printf("%d,%d,%d\n",y1-y0,(m1-m0),30-(d0-d1));}
    else {
   if (m1<m0) printf("%d,%d,%d\n",y1-y0-1,12-(m0-m1),(d1-d0));
     else printf("%d,%d,%d\n",y1-y0,(m1-m0),(d1-d0));
}
}
4.23
#include "stdio.h"

void main()
{
  int i=0;
  scanf("%d",&i);
  if (!(i%2))
  printf("even number\n");
  else printf("odd number\n");
}

4.24
#include "stdio.h"

void main()
{
  double x,y,z;
  scanf("%lf%lf%lf",&x,&y,&z);
  if(x>=y){
    if(x>=z) printf("%f\n",x);
    }
    else {
   if(y<=z) printf("%f\n",z);
     else printf("%f\n",y);
   }

}

4.25只用一种形式给出
#include "stdio.h"

void main()
{
  double x,y;
  scanf("%lf",&x);
  if ((x>-5)&&(x<0)) printf("%f",x);
  else if(x==0) printf("%f",x-1);
        else if ((x>0)&&(x<10)) printf("%f",x+1);
}