C实现大小写字母的转换

#include <stdio.h>

int main(int argc, const char *argv[])
{
    
    
	char ch;
	printf("input one charactor:");
	ch = getchar();
#if 0
	if(ch >= 'A' && ch <= 'Z' || ch >= 'a' && ch <= 'z')
		putchar(ch > 'Z' ? ch - 32 : ch + 32);
#endif

#if 1
	if(ch >= '0' && ch <= '9')
		puts("it`s a number !");
	else if(ch >= 'A' && ch <= 'Z')
	{
    
    
		putchar(ch + 32);
		putchar(10);
	}
	else if(ch >= 'a' && ch <= 'z')
	{
    
    
		putchar(ch - 32);
		putchar(10);
	}
	else
		puts("error !");
#endif
	return 0;
}

测试结果