The storage of a co!outer system is either internal storage or external storage. Internal storage commonly called memory is a component a computer system. Co!puter devices that aid the memory in holding data, information or programs are referred to as secondary or auxiliary storage devices.
By the time you complete this lesson, you should be able to:
- differentiate between an internal storage and external storage devices
- convert measurement units
- estimate the size of a file
Memory, or primary storage, works with the Central Processing Unit (CPU) to hold instructions and data to be processed. Memory keeps the instructions and data temporarily for whatever programs you happen to be using at the moment. It is the first place data and instructions are placed after being input; processed information is placed in memory to be returned to an output device. It is very important to know that memory can hold data only temporarily because it requires a continuous flow of electrical current. If current is interrupted, data is lost. Memory is in the form of a semiconductor or silicon chip and is contained inside the computer.
There are two types of memory: ROM and RAM. ROM is read only memory. It contains programs and data that are permanently recorded when the computer is manufactured. It is read and used by the processor, but cannot be altered by the user. RAM is random access memory. The user can access data in RAM memory randomly. RAM can be erased or written over at will by the computer program or the computer user.
Memory is sometimes referred to as temporary storage because it will be lost if the electrical power to the computer is disrupted or cut off. Data and instructions are held in memory only as long as the electrical power to the computer is on. Memory is located the system unit on tiny memory chips.
One of the most important facts to know about memory is that part of its content is held only temporarily. In other words, it is stored only as long as the microcomputer is turned on. When you turn the machine off, the contents immediately vanish. We have said this before, but it bears repeating: The stored contents in memory are volatile and can vanish very quickly, as during a power failure, for example. It is therefore a good practice to repeatedly save your work in progress to a secondary storage medium such as a pen drive or hard disk.
For instance, if you are writing a report with a word processor, every 5 to 10 minutes you should stop and save your work. Some word processors and other application software have the ability to automatically save every few minutes.
Memory is measured in bytes. A byte is usually made up of 8 bits and represents one character – a letter, digit, or symbol. The number of bytes that can be held is a measure of the memory and storage capacity.
Bytes are usually measured in groups of kilobytes, megabytes, gigabytes, and terabytes. The following chart defines each term.
|Kilobyte||KB||approximately 1,000 bytes|
|Megabyte||MB||approximately 1,000,000 bytes|
|Gigabyte||GB||approximately 1,000,000,000 bytes|
|Terabyte||TB||approximately 1,000,000,000 bytes|
Since we have said that memory is in the form of chips and must maintain a constant flow of electricity, there must be a more permanent form of storage that does not depend on a constant flow of electricity. That form of storage is called secondary or auxiliary storage. The benefits of secondary storage are large space capacity, reliability, convenience and economical.
A hard disk, an internal disk, is a metal platter coated with magnetic oxide that can be magnetized to represent data. Hard disks come in a variety of sizes and can be assembled into a disk pack. Hard disks for personal computers are 3 ½” disks in sealed modules. Hard disks for personal computers are measured in gigabytes.
While the size or data capacity of a hard drive is very important, the speed of accessing that data is equally as important. Files on hard drives can be accessed significantly faster and more conveniently than floppy drives.
The ever-demanding need for storage has required even better storage capacity than that of magnetic disks. Optical disk technology meets that need. Included in the list of this type of technology is the optical disk, the CD-ROM or DVD-ROM. The CD-ROM, compact disk read-only storage can hold more than 660 MBs per disk. The new storage technology that outpaces all others is called DVD-ROM, digital versatile disk. The DVD has a 4.7 GB capacity, which is about seven times that of the CD-ROM.
In order to protect the data on your hard drive, you should have a backup system. A backup system is way of storing data in more than one location.
Magnetic tape is usually used for this purpose. Magnetic tape is an inexpensive type of storage; it looks like the tape used in audio cassettes.
Estimating File Size
Let’s use the following statement to understand how to estimate the size of a file.
Consider the statement Today is Saturday.
In the example, the statement is a text file and comprises:
(a) today – 5 characters
(b) is – 2 characters
(c) Saturday – 8 characters
(d) a space after today – 1 character
(e) a space after is – 1 character
(f) a period – 1 character
In all we have 18 characters from the statement.
Since 1 character is approximately 1 byte, we conclude that the statement is approximately 18 bytes.