#include <stdio.h>
int main(void)
{
    for (char a = 32; a < 127; a++)
        printf("a=%cn", a);
    return 0;
}

#include <stdio.h>
int main(void)
{
    for (unsigned char a = 32; a < 127; a++)
        printf("a=%cn", a);
    return 0;
}

#include <stdio.h>
int main(void)
{
    for (unsigned char a = 128; a < 256; a++)
        printf("a=%cn", a);

    return 0;
}