程序代码：

(1) A、double fun(int x,int y);

(2) B、12

(3) (x>y) ? z=x+y : z= x-y

(4) auto int

(5) <表达式1> ? <表达式2> : <表达式3>

(6) a[0][0]=(10),a[1][1]= (12),a[2][2]= (1)

(7) 2

(8) 668977

(23) 1996035432

(24) 6  8

(25) 
p=FFEE
&x=FFEE
*p=10
x=10

(26)
#include <stdio.h>
int main(void) {
    int i, j, k;

    for(i = 1; i<4 ; i++) {
        for(j=1 ; j<=4-i; j++) {
            k =  i * j;
            printf("%d*%d=%d ", i, j, k);
        }
        printf("\n");
    }
    return 0;
}

(27) 9
#include <stdio.h>

int main(void) {
    char str[81];
    char *p = str;
    int num;
    num = 0;
    gets(p);

    while(p[num]!='\0') {
        num++;
    }

    printf("The length of string is %d\n" , num);
    return 0;
}

(28)
5
7
10
14
15
20
21
25
28
30
35
40
42
45
49
50
55
56
60
63
65
70
75
77
80
84
85
90
91
95
98
100

(29)
#include <stdio.h>

void swap(int *x, int *y) {
    int t;
    t = *x;
    *x = *y;
    *y = t;
}

int main(void) {
    int a = 7, b = 8, *p = &a, *q = &b;
    printf("a = %d, b = %d\n", a,  b);
    swap(p, q);
    printf("a = %d, b = %d\n", a,  b);
    return 0;
}