#include
int conversion(int txt);

int main ()
{
int ch1;

printf("대소문자 변환기:");
ch1=getchar();
conversion(&ch1);
putchar(ch1);
}
int conversion(int txt)
{
int num1='a'-'b';

if (txt>='A' && txt<='Z')
return txt+num1;
else if (txt>='a' && txt<='z')
return txt-num1;
else
return -1;
}

부탁드립니다 ㅠㅠ

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