1     
 2 
 3 toupper
 4     
 5 
 6   原型：extern int toupper(int c);
 7   
 8   用法：#include <ctype.h>
 9   
10   功能：将字符c转换为大写英文字母
11   
12   说明：如果c为小写英文字母，则返回对应的大写字母；否则返回原来的值。
13   
14   举例：
15 
16 
17       // toupper.c
18       
19       #include <syslib.h>
20       #include <ctype.h>
21 
22       main()
23       {
24         char *s="Hello, World!";
25         int i;
26         
27         clrscr();        // clear screen
28         printf("%s\n",s);
29         for(i=0;i<strlen(s);i++)
30         {
31           putchar(toupper(s[i]));
32         }
33         
34         getchar();
35         return 0;
36       }

//---------------------------------1
#include <stdio.h>
#include<stdlib.h>
void main()
{
    printf("0 & 0 is %d\n", 0 & 0);
    printf("0 & 1 is %d\n", 0 & 1);
    printf("1 & 1 is %d\n", 1 & 1);
    printf("1 & 2 is %d\n", 1 & 2);
    printf("15 & 127 is %d\n", 15 & 127);
    system("pause");
}
//------------------------------2
#include <stdio.h>
#include<stdlib.h>
void main()
{
    int value = 0xFF;

    printf("The inverse of %X is %X\n", value, ~value);
    system("pause");
}
//-------------------------------3
#include <stdio.h>
#include<stdlib.h>
void main()
{
    printf("0 | 0 is %d\n", 0 | 0);
    printf("0 | 1 is %d\n", 0 | 1);
    printf("1 | 1 is %d\n", 1 | 1);
    printf("1 | 2 is %d\n", 1 | 2);
    printf("128 | 127 is %d\n", 128 | 127);
    system("pause");
}
//------------------------------------4
#include <stdio.h>
#include<stdlib.h>
void main()
{
    printf("0 ^ 0 is %d\n", 0 ^ 0);
    printf("0 ^ 1 is %d\n", 0 ^ 1);
    printf("1 ^ 1 is %d\n", 1 ^ 1);
    printf("1 ^ 2 is %d\n", 1 ^ 2);
    printf("15 ^ 127 is %d\n", 15 ^ 127);
    system("pause");
}
//------------------------------------5
#include <stdio.h>
#include<stdlib.h>
void main()
{
    printf("The letter is %c\n", 'A');
    printf("The letter is %c\n", 65);
    system("pause");
}
//---------------------------------------6
#include <stdio.h>
#include<stdlib.h>
void main()
{
    char letter;

    int vowel_count = 0;
    int consonant_count = 0;

    for (letter = 'A'; letter <= 'Z'; letter++)
        switch (letter) {
        case 'A':
        case 'E':
        case 'I':
        case 'O':
        case 'U': vowel_count++;
            break;
        default: consonant_count++;
    };

    printf("The number of vowels is %d\n", vowel_count);
    printf("The number of vowels is %d\n", consonant_count);
    system("pause");
}
//------------------------------------------------------------7
#include <stdio.h>
#include <conio.h>
#include <ctype.h>
#include <stdlib.h>

void main()
{
    char letter;

    do {
        printf("A Display directory listing\n");
        printf("B Display disk information\n");
        printf("C Change system date\n");
        printf("Q Quit\n");
        printf("Choice: ");

        letter = getchar();
        letter = toupper(letter);

        if (letter == 'A')
            system("DIR");
        else if (letter == 'B')
            system("CHKDSK");//不能用
        else if (letter == 'C')
            system("DATE");
    } while (letter != 'Q');
    system("pause");
}