| Memories
are made of this
System memory
The system memory is the place where the computer holds current
programmes and data that are in use. The term “memory”
is somewhat ambiguous as it can refer to many different parts of
the PC. As we have been talking about hard disks, CDs and various
types of removable storage devices during the past few months you
already know that there are so many different kinds of memory that
a PC uses.
However, “memory”
usually refers to the main system memory, which holds the instructions
that the processor executes and the data that those instructions
work with. Your system memory is an important part of the main processing
subsystem of the PC, tied in with the processor, cache, motherboard
and chipset.
Read
Only Memory (ROM)
Imagine being able to think but not being able to remember anything!
That is basically what the processor is (even though it has a tiny
bit of memory of its own), so it needs the support of various types
of memory to hold the data it processes. Apart from the needs of
the processor, there is a host of functions that the computer needs
to perform as soon as you switch on its power. In simple terms,
the processor usually doesn’t have a clue about these functions,
so the computer employs a type of ROM to store these functions so
that the computer knows how to boot up. These instructions are called
the system BIOS programme and is stored in the BIOS ROM. There are
various types of ROM too. Read Only Memory usually refers to a permanent
type of memory that cannot be modified, but there are variations
of these that accommodate different levels of flexibility.
ROM:
A regular ROM is constructed from hard-wired logic, encoded in the
silicon itself, much the way that a processor is. It is designed
to perform a specific function and cannot be changed. ROMs are only
used generally for programmes that are static (not changing often)
and mass-produced.
Programmable
ROM (PROM): This is a type of ROM that can be programmed using special
equipment; it can be written to, but only once. This is similar
to the way a CD-ROM recorder works by letting you “burn”
programs onto blanks once and then letting you read from them many
times.
Erasable
Programmable ROM (EPROM): An EPROM is a ROM that can be
erased and reprogrammed. This technology is analogous to a reusable
CD-RW.
Electrically Erasable Programmable ROM (EEPROM): The next level
of flexibility is the EEPROM, which can be erased under software
control. This is the most flexible type of ROM, and is now commonly
used for holding BIOS programs. Here we are blurring the line a
bit between what “read-only” really means, but remember
that this rewriting is done maybe once a year or so, compared to
real read-write memory (RAM) where rewriting is done often many
times per second!
Random
Access Memory (RAM)
The kind of memory used for holding programmes and data
that is currently being executed is called random access memory.
RAM differs from ROM in that it can be both read and written. It
is considered volatile storage because unlike ROM, the contents
of RAM are lost when the power is turned off. RAM is also sometimes
called read-write memory or RWM.
This is actually
a much more precise name, though it is hardly ever used. It’s
a better name because calling RAM “random access” implies
to some people that ROM isn’t random access, which is not
true. RAM is called “random access” because earlier
read-write memories were sequential and did not allow random access.
Obviously, RAM needs to be ‘writeable’ in order for
it to do its job of holding programmes and data that you are working
on.
The volatility
of RAM also means that you risk losing what you are working on unless
you save it frequently. RAM is much faster than ROM, due to the
nature of how it stores information and there are many different
types of RAMs, including static RAM (SRAM) and many flavours of
dynamic RAM (DRAM) which we will discuss next week. Until then take
care and keep those emails rolling in.
Improve
your computer literacy
Instruction cycle - The time period during which one instruction
is fetched from memory and executed when a computer is given an
instruction in machine language. There are typically four stages
of an instruction cycle that the CPU carries out:
- Fetch the
instruction from memory. This step brings the instruction into
the instruction register, a circuit that holds the instruction
so that it can be decoded and executed.
- Decode the
instruction.
- Read the
effective address from memory if the instruction has an indirect
address.
- Execute the
instruction.
Steps 1 and
2 are called the fetch cycle and are the same for each instruction.
Steps 3 and 4 are called the execute cycle and will change with
each instruction.
The term refers to both the series of four steps and also the amount
of time that it takes to carry out the four steps. An instruction
cycle also is called machine cycle. Webopedia.com
Techno
picks
Most outstanding MP3 CD player
With a thin design, a full-featured remote, and skip-free operation,
iRiver’s first-generation, superthin MP3 CD player, the SlimX
iMP-350, set a new standard for the category. Now the company is
serving up the iMP-400, which delivers the same performance and
features as its predecessor but improves upon its design.
www.iriver.com
Best
virtual studio
If you want a roomful of audio gear but don’t have the money,
get “Reason”. It’s as close as you can get. A
recording studio can be daunting because the mass of knobs, cables,
and audio gear associated with music production makes even the most
modest project studio intimidating and expensive. Happily, you can
ditch all that junk and just use Reason. This programme from Propellerhead
Software is a virtual audio studio that simulates everything from
mixers to synthesizers. Reason’s quality stands up to the
demands of all but the most professional composers, and if you don’t
have the space or the cash for a full studio, Reason is an impressive
alternative.
www.propellerheads.se
Best
P2P application
Despite legal wrangling, Sharman Networks has released a leaner
version of its popular P2P app. Kazaa allows you to download groups
of songs as a single item, search the Web from within the program,
and includes a new rating feature that keeps you from downloading
corrupt files - a move that counters efforts by record companies
and movie studios to dilute networks with erroneous records.
The only hitch
is the add-ware that can be a menace at times. www.kazaa.com
Top music organizer MoodLogic ingeniously organizes digital music,
and has the ability to correct and standardize song, artiste, and
album names. But for now, try the free version and wait for future
releases.
MoodLogic is
an online music database, organizer, and playlist generator that
catalogs music files; corrects ID3 tags, song titles, and album
and artiste names; organizes music; and lets you profile your own
songs and contribute to the MoodLogic database.
It’s also a virtual DJ: you tell the programme what music
genre or tempo you’re in the mood to hear, and MoodLogic serves
up the tunes to match; from your own collection, of course.
- Courtesy Cnet.com |
