1 //第二题
 2 
 3 #include <stdio.h>
 4 
 5 int main (void){
 6     int i;
 7     
 8     for (i=1;i<=10;++i){
 9         printf ("the square of i is %i.\n", i * i);
10     }
11     
12     return 0;
13 } 
  1 //第三题
  2 
  3 #include <stdio.h>
  4 
  5 int main (void){
  6     int triangularNumber,n;
  7     
  8     for (n=5;n<=50;n+=5){
  9         triangularNumber = n*(n + 1) / 2;
 10         printf ("triangularNumber is %i.\n", triangularNumber);
 11     }
 12     
 13     return 0;
 14 } 
 15 
 16 //第四题
 17 
 18 #include <stdio.h>
 19 
 20 int main (void){
 21     int n, multipleNum;
 22     
 23     multipleNum = 1;
 24     for (n=1;n<=10;++n){
 25         multipleNum *= n;
 26         printf ("the number %i possesses multipleNum %i.\n", n, multipleNum);
 27     }
 28     return 0;
 29 } 
 30 
 31 //第五题
 32 
 33 #include <stdio.h>
 34 
 35 int main (void){
 36     int n, two_to_the_n;
 37     
 38     printf ("TABLE OF POWERS OF TWO\n\n");
 39     printf (" n 2 to the n\n");
 40     printf ("--- --------------\n");
 41     
 42     two_to_the_n = 1;
 43     for(n=0;n<=10;++n){
 44         printf ("%2i %i\n",n,two_to_the_n); 
 45         two_to_the_n *= 2;
 46     }
 47     return 0;
 48 } 
 49 
 50 //第八题
 51 
 52 #include <stdio.h>
 53 
 54 int main (void){
 55     int i,n, number, triangularNumber, counter;
 56     
 57     printf ("How many times do you want?");
 58     scanf ("%i", &i);
 59     for (counter=1;counter <= i;++counter){
 60         printf ("what triangular number do you want?");
 61         scanf ("%i", &number);
 62         
 63         triangularNumber = 0;
 64         
 65         for (n=1; n<=number; ++n)
 66             triangularNumber += n;
 67         
 68             printf ("Triangular number %i is %i \n\n", number, triangularNumber);
 69     }
 70     
 71     return 0;
 72 } 
 73 
 74 //第九题
 75 //5.2
 76 
 77 #include <stdio.h>
 78 
 79 int main (void){
 80    int n, triangularNumber;
 81    
 82    triangularNumber = 0;
 83    n = 1;
 84    while (n <= 200){
 85        triangularNumber += n;
 86        ++n;
 87    }
 88     printf ("The 200th triangular number is %i\n", triangularNumber);
 89     
 90     return 0;
 91 } 
 92 
 93 //5.3
 94 
 95 #include <stdio.h>
 96 
 97 int main(void){
 98     int n, triangularNumber;
 99     printf ("TABLE OF TRIANGULAR NUMBERS\n\n");
100     printf (" n    Sum from 1 to n\n");
101     printf ("---   ----------------\n");
102     
103     triangularNumber = 0;
104     n =1;
105     while (n<=10){
106         triangularNumber += n;
107         printf ("%2i             %i\n",n,triangularNumber);
108         ++n;
109     }
110     return 0;
111 }
112 
113 //5.4
114 
115 #include <stdio.h>
116 
117 int main (void){
118     int n, number, triangularNumber;
119     
120     printf ("What triangular number do you want?");
121     scanf ("%i", &number);
122     
123     triangularNumber = 0;
124     n =1;
125     while (n <= number){
126         triangularNumber += n;
127         ++n;
128     }
129     printf ("Triangular number %i is %i\n", number, triangularNumber);
130     
131     return 0;
132 }
133 
134 //5.5
135 
136 #include <stdio.h>
137 
138 int main (void){
139     int n, number, triangularNumber, counter;
140     
141     counter = 1;
142     while (counter <= 5){
143         printf ("What triangular number do you want? ");
144         scanf ("%i", &number);
145         
146         triangularNumber = 0;
147         n = 1;
148         
149         while (n <= number){
150             triangularNumber += n;
151             ++n;
152         }
153         printf ("Triangular number %i is %i\n\n",number,triangularNumber);
154         
155         ++counter;
156     }
157     
158     return 0;
159 }
160 
161 //第十一题
162 
163 #include <stdio.h>
164 
165 int main(void){
166     int number, sum, right_digit;
167     
168     printf ("Please enter an integer:");
169     scanf ("%i", &number);
170     
171     sum = 0;
172     while (number != 0){
173         right_digit = number % 10;
174         sum += right_digit;
175         number /= 10;
176     }
177     printf ("The sum of whole digits is %i\n", sum);
178     
179     return 0;
180 }