Evolution of Memory

EVOLUTION OF STORAGE MEMORY

Year	Memory Type	Details	Limitations
1750	Punch Card	90mm*215mm (Varying sizes).	Difficult to handle trays of cards.
1845	Punched Tapes	Punched tape consists of a long strip of paper in which holes are punched to store data.	Relaibility(easily tampered) Vulnerable(Handling care)
1877	Phonograph	Machine that stored recorded voice and printed on paper.	Only voice could be stored. Voice distortion.
1898	Telegraphone	It was the first practical apparatus for magnetic sound recording and reproduction.	Affected by magnetic field. Records were recorded in one take.
1928	Magnetic Tape	The recording medium was a 1/2 inch wide thin band of nickel-plated bronze. Recording density was 128 characters per inch on eight tracks	Suffer from deterioration. Analog medium. Wear-tear due to over use.
1932	Magnetic Drum	Read and write heads were mounted at a distance of some micrometers that produced an electro magnetic pulse. Binary values of 0 or 1 are recorded by generating electric pulses while the drum is rotating. Formed bases for HDD.	Not portable. Slow access time. Linear access.
1946	William Tube	The first random access computer memory, through using electrostatic cathode-ray display tubes as digital stores.(1KB-2KB)	Occupied a large space. Expensive machinery deployed to generate the specific charges. Volatile Memory.
1946	Selectron Tube	Storage increased to 4KB used 5’’x3’’Vacuum Tubes	Data losses if discharged. Volatile Memory
1949	Delay Line Memory	Serial line memory used mercury to store data.	Serial Access. Volatile Memory.
1949	Magnetic Core	It uses small magnetic ceramic rings, the cores, to store information via the polarity of the magnetic field they contain. Non-volatile,Portable.	Affected by magnetic field.
1956	Hard Disk	A hard disk uses rigid rotating platters. It stores and retrieves digital data from a planar magnetic surface. The first computer with a hard disk drive as standard was the IBM 350 Disk File, introduced in 1956 with the IBM 305 computer. This drive had fifty 24 inch platters, with a total capacity of five million characters.	Not portable. The storage capacity of the 305's 50 two-foot diameter disks was 5 megabytes of data.
1963	Music Tape	The compact audio cassette audio storage medium was introduced by Philips in 1963. The compact cassette had originally been intended for use in dictation machines, but soon became, and remains, a popular medium for distributing prerecorded music.	Physical contact with read head cause wear-tear. Deteriotion.
1966	DRAM	Dynamic Random Access Memory (DRAM) cells, one-transistor memory cells that store each single bit of information as an electrical charge in an electronic circuit. This technology permitted major increases in memory density.	Volatile. Magnetic interference changed data.
1968	Twistor Memory	Similar to core memory, formed by wrapping or closing magnetic tape around a current-carrying wire. Non-volatile.	Used for a short period and was replaced by RAM chips. The main concern with core was the time needed to wire up all the small magnets, a task which grew in complexity as the density of the core planes was increased.
1970	Bubble Memory	It is conceptually a stationary disk with spinning bits. The unit, only a couple of square inches in size, contains a thin film magnetic recording layer.	Advancement of Twistor memory. Required a "warm-up" time of about 20 seconds.
1971 1976	8’’Floppy 5,25’’ Floppy	A floppy disk is a data storage device that is composed of a circular piece of thin, flexible (i.e. "floppy") magnetic storage medium encased in a square or rectangular plastic wallet.	Change due to magnetic field. Not durable.
1980	CD	A compact disc (or CD) is an optical disc used to store digital data, originally developed for storing digital audio.	Easy to scratch.
1984	CD-ROM	The CD-ROM, an abbreviation for “Compact Disk Read-Only-Memory”, is an optical data storage medium using the same physical format as the audio compact discs. Digital information is encoded at near-microscopic size, allowing a large amount of information to be stored.	Easy to scratch.
1987	DAT(Digital Audio Tape)	Digital Audio Tape (DAT or R-DAT) is a signal recording and playback medium introduced by Sony in 1987. In appearance it is similar to a compact audio cassette, using 4 mm magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. Still used as backup.	Same as audio cassettes.
1989	DDS(Digital Data Storage)	Digital Data Storage (DDS) is a format for storing and backing up computer data on magnetic tape that evolved from DAT technology. Still used.	Same as audio tapes.
1990 1992	MOD(Magneto-Optical disc) MD(MiniDisc)	Is an optical disc format that uses a combination of optical and magnetic technologies. The sizes of discs are usually 3.5'' or 5.25'', and disk capacities are usually one of 128MB/230MB/540MB/640MB/1.3GB/2.6GB.	Low quality than CD.
1994	Compact Flash	CompactFlash (CF) is a data storage device that uses the flash memory in a standardized enclosure. On a CF there is the memory as well as the controller (the electronic that writes and read the memory) and so the CF can be read by older devices as well.	Has a limit for no of writes.
1994	ZIP	Same as 3.5’’floppy but with higher storage.	Size limited to 750MB. Special zip readers needed to read/write data.
1995	DVD	DVD is the new generation of optical disc storage technology. DVD is essentially a bigger, faster CD that can hold cinema-like video, better-than-CD audio, still photos, and computer data.	Scratches.
1995	SmartMedia	A SmartMedia card consists of a single NAND flash EEPROM chip embedded in a thin plastic card. Its primary advantage was the lack of a built-in controller in the card, which kept the cost down(Laid foundation for memory cards). Typically, a SmartMedia card was used as storage media for a portable device, in a form that can easily be removed for access by a PC. For example, a digital camera would use a SmartMedia card for storing image files.	Easy to lose. Broken.
1995	Phase Writer	Optical Storage Device like CD-ROM.(unsuccessful)	Extinct due tough competition from DVD.
1996	AIT(Advanced Intelligent Tape)	Is a computer storage magnetic tape format. The AIT has a storage capacity that is forth times larger than the capacity of the DAT and is used as backup system only.  Backwards and forwards compatible.	Still used and developed.
1996	CD-RW	A CD-RW drive can write about 700MB of data to CD-RW media around 1000 times.	Scratch.
1997 1998 1999	MMC(Multimedia Card) Memory Stick Micro Drive	MMC is about the size of a postage stamp: 24mm x 32mm x 1.5mm. MMC originally used a 1-bit serial interface, but newer versions of the specification allow transfers of 4 or sometimes even 8 bits at a time.  Microdrives have a magnetic memory with a high capacity and a disc-diameter of 1 inch. These small hard disks can be easily destroyed by vibrations and too low air pressure.  Microdrives are usually used in PDAs and digital cameras.	Special reader to be installed.
2001	USB Key(Pen Drive)	Uses USB port to connect and is available in varying sizes   (1-32GB). Best for portability.	No. of writes limit(~1k).
2001	SD-Card(Secure Digital)	Is a flash memory memory card format. SD cards are based on MMC format, but add little-used DRM encryption features and allow for faster file transfers, as well as being physically slightly thicker.	Need card readers.
2003	Blu-Ray	Is a next-generation optical disc format meant for high definition video (HD) and high density data storage, and is one of two competing standards for HD optical media. Blu-ray gets its name from the shorter wavelength (405 nm) blue laser	Need blu-ray readers.
2004	HD-DVD	HD-DVD (High-Density Digital Versatile Disc) is a digital optical media format. HD-DVD has a single layer capacity of 15 GB and a dual-layer capacity of 30 GB. Toshiba has announced a triple-layer disc is in development, which would offer 45GB of storage.	Need reader/writers.

Comparison of Memory

Below is a comparison of memory of today and one twenty years before.

Stop Wasting CDs; Install Linux Straight from an ISO

GNU/Linux comes in many different flavours, apart from the fact that each individual distro has a new release almost every six months, if not less. I have a habit of trying out every new version the moment it comes out, and I’m sure many of you do too.

Now, let’s assume you have downloaded a new version of a distro and are in the mood to try it out right away. It’s past midnight and you realise that you’ve run out of blank CDs/DVDs. So you will have to wait till the morning when the shops open, to be able to burn the distro image in order to install it. I’m sure a lot of us often face this problem. In this article I’ll share a simple trick by which you can install the new distro without burning it to a CD/DVD. The only requirement is that you should have a pre-installed GNU/Linux system—which you already have, I assume.

All Linux installers use two files to boot a computer: a kernel and an initial root filesystem—also known as the RAM disk or initrd image. This initrd image contains a set of executables and drivers that are needed to mount the real root filesystem. When the real root filesystem mounts, the initrd is unmounted and its memory is freed. These two files are named differently in different distros—refer to Table 1 for their names.

Table 1: Names of kernel and RAM disk images in some popular distros
Distro	Kernel path	RAM disk path
Fedora	/isolinux/vmlinuz	/isolinux/initrd.img
RHEL5/CentOS5	/isolinux/vmlinuz	/isolinux/initrd.img
openSUSE	/boot/i386/loader/linux	/boot/i386/loader/initrd
Mandriva	/i586/isolinux/alt0/vmlinuz	/i586/isolinux/alt0/all.rdz
Ubuntu	/casper/vmlinuz	/casper/initrd.gz
Debian	/install.386/vmlinuz	/isolinux/initrd.img

The first thing you need to do is place the ISO image(s) inside a directory. Some installers are not able to read the ISO images if they are placed inside a directory. So, just to be on the safe side, place them in the root of the file system. The partition on the hard disk holding the ISO files must be formatted with the ext2, ext3 or vfat files system.

In our example, let’s go ahead and do it with an old Fedora 9 ISO image. Follow these steps to begin with:

# mkdir /fedora

# cp /home/sandeep/Fedora-9-i386-DVD.iso /fedora/fedora9.iso

Now extract the kernel and initrd files from the ISO image and place them in the same directory in which you placed the ISO. You can use File Roller, the archive manager for GNOME, to extract the files. Just right click on the ISO and select “Open with File Roller”. It displays the contents of the ISO image. Then navigate to theisolinux directory—in Fedora 9 these two files are placed inside the isolinux directory; it’s often different for other distros, so please refer to Table 1 for the paths. Select the kernel and initrd files, and extract them to the location where your ISO image exists.

The second method is to mount the ISO image and extract the files. Run the following commands to do this:

# mount -o loop /fedora/fedora9.iso /media/iso

# cd /media/iso/isolinux

# cp vmlinuz initrd.img /fedora/

I have mounted the ISO image without providing the -t iso9660 option (to specify the type of media as an ISO filesystem). It worked for me. If the above mount command doesn’t work, do add this option along with the rest of the mount command above.

Note: Fedora 10 has introduced a change in the Anaconda installer. So, in addition to the vmlinuz andinitrd.gz files, you will also need to copy the images/install.img file, create a directory called/fedora/images, and place the install.img file there.

Now, it’s time to edit the /boot/grub/menu.lst file on the system I’m currently using—Ubuntu 8.10. Note that this is the location of the Grub menu in almost all distros, except for Fedora/Red Hat, where it’s called/boot/grub/grub.conf. Append the following entry there:

title Install Linux

root (hdX,Y)

kernel /distro/Linux_kernel

initrd /distro/Ram_disk

In this case…

1.      ‘title’ is the name you want to display in your GRUB menu

2.      ‘root’ is the hard disk partition that contains the ISO image

3.      ‘kernel’ is the Linux kernel

4.      ‘initrd’ is the initial RAM disk image

Likewise, the menu.lst entry for the ISO file looks like what’s shown below:

title Install Fedora 9

root (hd4,0)

kernel /fedora/vmlinuz

initrd /fedora/initrd.img

Now you are ready to install your new Linux distro directly from the hard disk without the need for a CD/DVD drive. Reboot your system and select the ‘Install Fedora 9’ entry from your GRUB menu.

Figure 1 shows what the GRUB menu looks like after rebooting my system.

Obviously, I selected the ‘Install Fedora 9’ entry and it has started booting my system with the help of vmlinuzand initrd.img files. The set-up prompts me to choose a language and keyboard layout. Then it prompts me to select the ‘Installation Method’ as shown in Figure 2.

In this screen you need to select the ‘Hard drive’ option and proceed to the next screen. Here, you have to select the appropriate partition and the directory where the installation image exists. In my system, the installation image exists in the /fedora directory of /dev/sda5 partition. This is shown in Figure 3.

After this, it picks up the Anaconda installer of Fedora 9 (or any other installer, as in your case) from the prescribed location, and proceeds with the regular installation procedure just like you’d get if you were installing from a bootable optical media. Follow the steps as you would to install the distro. Figure 4 shows the package installation in action. After that’s done, reboot and you’ll be able to use your newly installed
operating system.

Easy enough, right? So, I hope you’ll start using this simple trick to install the newly released GNU/Linux distros and stop worrying about whether you have the required blank optical media. And the additional environmental benefit is less use of non-biodegradable plastic materials (which is what a CD/DVD is made out of)