Question

so I am shifting up a char into a long, then clearing, and doing it again. A shift of 15 makes my machine go wacky, see comment in code. What do you think is causing this.

This machine char 0x00, and long 0x0000 0000

    unsigned char temp;
    unsigned long open_code;

    temp = 0x01;
    open_code = open_code | (temp <<1);// open_code = 0x0000 0002 
    open_code = 0;
    //......    
    // 2 - 7    
    //....  
    temp = 0x01;
    open_code = open_code | (temp <<8); // open_code = 0x0000 0100 
    open_code = 0;  
    temp = 0x01;
    open_code = open_code | (temp <<9); // open_code = 0x0000 0200 
    open_code = 0;  
    temp = 0x01;
    open_code = open_code | (temp <<10); // open_code = 0x0000 0400 
    open_code = 0;  
    temp = 0x01;
    open_code = open_code | (temp <<11); // open_code = 0x0000 0800 
    open_code = 0;
    temp =  0x01;
    open_code = open_code | (temp <<12); // open_code = 0x0000 1000
    open_code = 0;  
    temp =  0x01;
    open_code = open_code | (temp <<13); // open_code = 0x0000 2000
    open_code = 0;  
    temp =  0x01;
    open_code = open_code | (temp <<14); // open_code = 0x0000 4000  
    open_code = 0;
    temp =  0x01;
    open_code = open_code | (temp <<15); // open_code = 0xFFFF 8000  !!!!!
    open_code = 0;
    temp =  0x01;
    open_code = open_code | (temp <<16); // open_code = 0x0000 0000  !!!!!

Answer 1

It looks like you’re shifting an unsigned char too far and as a result inducing overflow. Try casting it to a long before shifting, like so:

open_code = open_code | (((long)temp) <<15);