Re: [Pgubook-readers] Counters and register size

[Roger]

> On Tue, Nov 20, 2012 at 02:13:20PM -0800, Woolly Thinking wrote:
>The very simplest answer to register - cpu size is that it is the number of 
>wires that carry the cpu instructions or data.  This is a slight over 
>simplification but 16 bit cpu's basicaly use 16 wires, 32 bit cpu's use 32 
>wires, etc  When you hear that a computer has 64 bit addressability it means 
>that it has the wiring for 64 "on/off" states carried on the individual wires. 
> These in turn mean that 64 on-off states provide the highest binary number 
>that can be defined by that number of bits.  The  "word" originally came from 
>the concept of one individual wiring state that transmitted a computer logical 
>concept within a the limits of the cpu's wiring.  So a 16 bit computer's word 
>was 16 bits.  The wiring of a computer corresponds in all respects to this 
>word size.  Every register is 16 bits on a 16 bit computer.  
>
>The counter is a register that holds the address of the next executable 
>instruction.  This is a binary number that specifies an address in ram 
>(addressability).  This counter is incremented by the next fetch cycle.  It 
>can also be altered by programming in which the old value is saved (for later 
>restoration) and a new value provided.  This is the basis for all branch,  
>perform, and goto instructions in all languages.  Assembler does this but 
>requires programmer effort.

Well, I knew the answer was something like this, but figured somebody else 
could better word the answer then my attempt of simply being, "It's how the 
hardware was created."

And I should probably pipe in here that I just seem to have run into another 
really good book, aside from this ASM book, your friendly K&R book, Autotools 
book, Make book, it's "21st Century C" By Ben Klemens.

It really seems to fill all the gaps inbetween your other specialty books just 
mentioned.  Similar to learning ASM for writing Good C, "21st Century C" 
teaches the programmer all the stuff K&R left out while cancelling the 
confusion of Autotools and other issues.

I'm only on Chapter 1, but it's really looking good -- the beginning had a 
little too jokey, but that immediately seemed to clear-up.

Cheers!

-- 
Roger
http://rogerx.freeshell.org/