c - wrong initialization of a short bit by bit - why set incorrectly the most significant bits of the last two variables? -

i wrote program exercise myself bitwise operations. in follow lines of code try assign value 3 short bit-by-bit. print them through bit_print() function.

        #include <stdio.h>         #include <limits.h>          void bit_print(short a)         {             int   i;             int   n = sizeof(short) * char_bit;       /* in limits.h */             short   mask = 1 << (n - 1);              /* mask = 100...0 */              (i = 1; <= n; ++i) {                 putchar(((a & mask) == 0) ? '0' : '1');                 <<= 1;                 if (i % char_bit == 0 && < n)                     putchar(' ');             }         }          int main(void){             short alice = 0, betty = 0, carol = 0;             int x;             char c;              printf("put 16 bits alice: ");             (x = 15; x >= 0; --x){                 if ((c = getchar()) == '1')                     alice |= 1 << x;                 else                     alice |= 0 << x;             }             putchar('\n');              printf("put 16 bits betty: ");             (x = 15; x >= 0; --x){                 if ((c = getchar()) == '1')                     betty |= 1 << x;                 else                     betty |= 0 << x;             }             putchar('\n');              printf("put 16 bits carol: ");             (x = 15; x >= 0; --x){                 if ((c = getchar()) == '1')                     carol |= 1 << x;                 else                     carol |= 0 << x;             }             putchar('\n');              bit_print(alice);             putchar('\n');             bit_print(betty);             putchar('\n');             bit_print(carol);             putchar('\n');              return 0;         } 

for reason, if input 1111111111111111 3 times, executing program follow output:

put 16 bits alice: 1111111111111111  put 16 bits betty: 1111111111111111  put 16 bits carol: 1111111111111111  11111111 11111111 01111111 11111111 10111111 11111111 

as can see, significant bits of last 2 variables, betty , carol, have zeroes in places should not. why?

when using getchar(), newline character press end end of input gets picked up, you're not accounting it.

you'll need read , discard newlines @ end of each loop account this:

    #include <stdio.h>     #include <limits.h>      void bit_print(short a)     {         int   i;         int   n = sizeof(short) * char_bit;       /* in limits.h */         short   mask = 1 << (n - 1);              /* mask = 100...0 */          (i = 1; <= n; ++i) {             putchar(((a & mask) == 0) ? '0' : '1');             <<= 1;             if (i % char_bit == 0 && < n)                 putchar(' ');         }     }      int main(void){         short alice = 0, betty = 0, carol = 0;         int x;         char c;          printf("put 16 bits alice: ");         (x = 15; x >= 0; --x){             if ((c = getchar()) == '1')                 alice |= 1 << x;             else                 alice |= 0 << x;         }         putchar('\n');         getchar();          printf("put 16 bits betty: ");         (x = 15; x >= 0; --x){             if ((c = getchar()) == '1')                 betty |= 1 << x;             else                 betty |= 0 << x;         }         putchar('\n');         getchar();          printf("put 16 bits carol: ");         (x = 15; x >= 0; --x){             if ((c = getchar()) == '1')                 carol |= 1 << x;             else                 carol |= 0 << x;         }         putchar('\n');         getchar();          bit_print(alice);         putchar('\n');         bit_print(betty);         putchar('\n');         bit_print(carol);         putchar('\n');          return 0;     }