C语言转换大小写

#include <stdio.h>  
#include <ctype.h>  // Contains the tolower prototype  
void main (void)  
{  
    int letter;   
    for (letter = getchar(); ! feof(stdin); letter = getchar())  
        putchar(tolower(letter));  
} 

 

#include <stdio.h>  
#include <string.h>  
 
void main (void)    
{  
    char line[255];  // Line of text read     
    while (fgets(line, sizeof(line), stdin))  
        fputs(strupr(line), stdout);  
}  

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