Check if a char is ASCII using Bitmasks and Bit Operators in C

Question

I need to write program that will check each individual char from stdin to see if it is an ASCII character. I know that what it needs to check is if the 8th bit (7th in code, if I remember correctly) is a 0, since ASCII only uses 7 bits, but I'm having difficulty figuring out just how exactly to make it check the specific bit. This is what I have at time of writing.

#include <stdio.h>

#define MASK 7

int     main(void)
{

auto    char    inChar;

    do
    {
    inChar = getchar();

    // Breaks the do-while loop if it detects End of File
    if (inChar == EOF)
        {
        break;
        }

    printf("%c", inChar);

    if ( inChar == (0 & MASK))
        {
        printf("Not an ASCII Character.\n");
        }

    }while(1);

    puts("\n");

    return 0;
}

I am aware that I don't have the coder properly implemented to check every character value yet, but I will worry about that later. Right now I just need help with getting it to check that specific bit in the variable.

Also this is my first time asking here so please forgive any improper formatting of my question.

Answer 1

From ctype.h:

#define isascii(c)  ((c & ~0x7F) == 0)

Answer 2

You want the seventh bit, not the value 7.

/* 10000000 = 2^7 = 128 */

uint8_t b;
printf("Leftmost bit is %d\n", (b & 128) != 0);