c - Bitwise Concatenation -

i have following:

char *pointer = decimal_to_binary(192) // yields 11000000 char *pointer2 = decimal_to_binary(168) // yields 10101000 

i trying concat them into:

1100000010101000 

i referencing: concatenate binary numbers of different lengths , using:

unsigned long pointer3 = (*pointer << 16) | *pointer2; 

which gives output:

1100010000000000110001 

what doing wrong?

you don't show how print anything, makes difficult interpret question. however, statement irretrievably broken in nothing concatenate strings pointed @ pointer , pointer2:

unsigned long pointer3 = (*pointer << 16) | *pointer2; 

this takes first character pointer points @ (a 1) , shifts value left 16 bits, , adds (ors) in first character pointer2 points @ (another 1), , assigns integer format misnamed pointer3. thus, gets value:

pointer3 = 0x00310031; 

the question takes interpretation, making plausible (but not accurate) assumptions, code might you're after:

#include <stdio.h> #include <stdlib.h> #include <string.h>  static char *decimal_to_binary(unsigned char byte) {     char *result = malloc(9);     if (result != 0)     {         char *digit = result;         (int = 0; < 8; i++)             *digit++ = ((byte >> (7 - i)) & 0x01) + '0';         *digit = '\0';     }     return result; }  int main(void) {     char *pointer1 = decimal_to_binary(192);     char *pointer2 = decimal_to_binary(168);     char  concatenated[17];     unsigned long pointer3 = (*pointer1 << 16) | *pointer2;      strcpy(&concatenated[0], pointer1);     strcpy(&concatenated[8], pointer2);      printf("p1 = <<%s>>; p2 = <<%s>>; p3 = 0x%08lx; c = <<%s>>\n",            pointer1, pointer2, pointer3, concatenated);      free(pointer1);     free(pointer2);     return(0); } 

output:

p1 = <<11000000>>; p2 = <<10101000>>; p3 = 0x00310031; c = <<1100000010101000>> 

note code using decimal_to_binary() not take care avoid (mis)using null pointers. design of decimal_to_binary() less stellar; free() calls forgotten. better design be:

void decimal_to_binary(unsigned char byte, char buffer[9]); 

where calling code provides buffer binary output written. there other ways of writing loop in decimal_to_binary(); might more efficient 1 chosen here.