There is a bug common to all 5 versions: we should always test whether the read was successful.

• For scanf(): did it return 1, when we asked for one conversion?
• For getchar(): did it return EOF?

Note, in particular, that narrowing the result of getchar() (which is int) to an unsigned char loses the ability to distinguish EOF from a valid character.

Here's a corrected version:

#include <stdio.h>

int main(void)
{
    int d;
    while ((d = getchar()) != EOF) {
        if (d != '\n')
            printf("%d\n", d * d);
    }
}

Finally, a pedantic note: this will only work on ASCII values when run on an ASCII system/locale. In other words, C always uses the environment's character coding, and does not convert input to a fixed representation as done by, say, Java.

There is a bug common to all 5 versions: we should always test whether the read was successful.

• For scanf(): did it return 1, when we asked for one conversion?

• For getchar(): did it return EOF?

  Note, in particular, that narrowing the result of getchar() (which is int) to an unsigned char loses the ability to distinguish EOF from a valid character.

Here's a corrected version:

#include <stdio.h>

int main(void)
{
    int d;
    while ((d = getchar()) != EOF) {
        if (d != '\n')
            printf("%d\n", d * d);
    }
}

Finally, a pedantic note: this will only work on ASCII values when run on an ASCII system/locale. In other words, C always uses the environment's character coding, and does not convert input to a fixed representation as done by, say, Java.

There are some bugs common to all 5 versions:

• It's undefined behaviour to pass a pointer to unsigned char when using %c; in practice, you'll usually get away with this one.
• We should always test whether the read was successful. For getchar(): did it return EOF? For scanf(): did it return 1, when we asked for 1 conversion?

Note, in particular, that narrowing the result of getchar() (which is int) to an unsigned char loses the ability to distinguish EOF from a valid character.

Here's a corrected version:

#include <stdio.h>

int main(void)
{
    int d;
    while ((d = getchar()) != EOF) {
        if (d != '\n')
            printf("%d\n", d * d);
    }
}

Finally, a pedantic note: this will only work on ASCII values when run on an ASCII system/locale. In other words, C always uses the environment's character coding, and does not convert input to a fixed representation as done by, say, Java.

There is a bug common to all 5 versions: we should always test whether the read was successful.

• For scanf(): did it return 1, when we asked for one conversion?
• For getchar(): did it return EOF?

Note, in particular, that narrowing the result of getchar() (which is int) to an unsigned char loses the ability to distinguish EOF from a valid character.

Here's a corrected version:

#include <stdio.h>

int main(void)
{
    int d;
    while ((d = getchar()) != EOF) {
        if (d != '\n')
            printf("%d\n", d * d);
    }
}

Finally, a pedantic note: this will only work on ASCII values when run on an ASCII system/locale. In other words, C always uses the environment's character coding, and does not convert input to a fixed representation as done by, say, Java.