From: bc@nospicedham.freeuk.com   
      
   On 21/01/2018 08:05, Veek M wrote:   
   > Reading Ray Seyfarth - x86/Yasm assembly language. In it he uses the   
   following   
   >   
   > segment .data:   
   >      a dq 175   
      
   I assume 'a' is a label, normally written as 'a:'.   
      
      
   > segment .text   
   > global main   
   > main:   
   >      mov rax, [a]   ; to store the value of 'a' in rax   
      
   Wait, what do you mean its 'value'? 'a' is the address of a location   
   which contains 175 in a 64-bit format.   
      
   [a] is used to access the memory at address a. In this case, it will   
   read 175 at address a into register rax.   
      
   To load the address itself to rax, you'd use one of:   
      
      mov rax,a           ; load address   
      lea rax,[a]         ; load effective address, same as a, here   
      
   >   
   > But then he does:   
   >   
   >      mov [a], rax; which ought to mean he's storing a value in the   
   value-of-a.   
      
   Here, the contents of rax are stored to memory at address 'a'.   
   Overwriting the 175.   
      
   >Therefore [a] is a pointer in this case? Is that so or is he storing in 'a'   
   somehow - slings and arrows of outrageous syntax?   
   >   
      
    > Thus leading to the conclusion [] acts as a de-reference operator.   
      
   In HLLs, 'dereferencing' is usually applied to pointer operations, not   
   normal variable accesses:   
      
      static int  a;         // 32-bit int   
      static int* p;         // 64-bit pointer to 32-bit int   
      
      &a;    // mov rax,a   load address of variable   
      a;     // mov eax,[a] load variable value (not called a dereference)   
      p;     // mov rax,[p] load pointer value, not its target   
      *p;    // mov rax,[p]; mov eax,[rax] deference pointer   
      
   --   
   bartc   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)