Simple encryption program

in C i am trying to do a simple encryption that gets the ASCII value of the character then doubles it and subtracts 25 then to decrypt adds 25 and divides by 2 but it does not seem to be working here is the relevant code.I am using Dev C++ and am just learning the WIN32 API so i have copied and modified most of this code from a tutorial.

Code:

case IDC_MAIN_EDIT:
    {
    int len = GetWindowTextLength(GetDlgItem(hwnd, IDC_MAIN_EDIT));
    if(len > 0)
    {
    int i,j;
    char* buf;
    buf = (char*)malloc( len + 1);
    GetDlgItemText(hwnd, IDC_MAIN_EDIT, buf, len + 1);
   
    //... do stuff with text ...
    for (i=0;i<len;i++)
    {
        j = buf[i];
   //     if(j >> 1 > 255)
       
        j = (j  * 2)^ (1/2);
        buf[i] =j;
    }
    SetDlgItemText(hwnd, IDC_MAIN_ENC,buf );
    
    GlobalFree((HANDLE)buf);
    }
else
SetDlgItemText(hwnd, IDC_MAIN_ENC,"" );
        
    }  
break;

case IDC_MAIN_ENC:
    {
    int len = GetWindowTextLength(GetDlgItem(hwnd, IDC_MAIN_ENC));
    if(len > 0)
    {
    int i,j;
    char* buf;
    buf = (char*)malloc( len + 1);
    GetDlgItemText(hwnd, IDC_MAIN_ENC, buf, len + 1);
   
    //... do stuff with text ...
    for (i=0;i<len;i++)
    {
        j = buf[i];
       // if((j << 1)>255)
       
        j = j ^ 2 /2;
        buf[i] =j;
    }
    SetDlgItemText(hwnd, IDC_MAIN_EDIT,buf );
    
    GlobalFree((HANDLE)buf);
    }
else
SetDlgItemText(hwnd, IDC_MAIN_EDIT,"" );
        
    }  
break;

Thanks