常言道：学以致用。不但既要学会，而且还要懂得运用。

很久之前，自学C语言。

在学到 putchar 函数的时候，对着 ASCII 代码对照表，写了一套“计算题”，

把代码复制进编译器，然后运行编译，它会列出一道简单的计算题（加减法），把算出的结果敲进去，会得到一个字符。连续做完七道计算题后，它会把你得到的字符整理成一个句子。如果算得不对，你会得到一串很奇怪的句子。

代码如下：

#include <stdio.h>
int main()
{
    int a, b, c, answer,
        a1, a2, a3, a4, a5, a6, a7;
    printf("a = 15, b = 58\n\nIf a+b\n");
    a = 15; b = 58;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a + b;
    a1 = answer;
    if (a + b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a1); printf("\n\n");
    }
    printf("a = 13, b = 63\n\nIf a+b\n");
    a = 13; b = 63;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a + b;
    a2 = answer;
    if (a + b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a2); printf("\n\n");
    }
    printf("a = 102, b = 23\n\nIf a-b\n");
    a = 102; b = 23;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a - b;
    a3 = answer;
    if (a - b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a3); printf("\n\n");
    }
    printf("a = 27, b = 59\n\nIf a+b\n");
    a = 27; b = 59;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a + b;
    a4 = answer;
    if (a + b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a4); printf("\n\n");
    }
    printf("a = 96, b = 27\n\nIf a-b\n");
    a = 96; b = 27;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a - b;
    a5 = answer;
    if (a - b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a5); printf("\n\n");
    }
    printf("a = 90, b = 1\n\nIf a-b\n");
    a = 90; b = 1;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a - b;
    a6 = answer;
    if (a - b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a6); printf("\n\n");
    }
    printf("a = 15, b = 70\n\nIf a+b\n");
    a = 15; b = 70;
    printf("Your answer is ");
    scanf_s("%d", &answer);
    printf("\n");
    c = a + b;
    a7 = answer;
    if (a + b == answer)
    {
        printf("Congratulation! ");
        printf("You get letter : ");
        putchar(c); printf("\n\n");
    }
    else
    {
        printf("No correct! ");
        printf("You get letter : ");
        putchar(a7); printf("\n\n");
    }
    printf("Now make a sentence out of the letters you collected.\n\n");
    putchar(a1);
    putchar('\t');
    putchar(a2); putchar(a3); putchar(a4); putchar(a5);
    putchar('\t');
    putchar(a6); putchar(a3); putchar(a7);
    printf("\n\n");
    return 0;
}

反复验证计算了好几遍，应该是没有错误了。

正确计算结果为：

I love you