Advanced Photography Course

CPU PRIMARY AND SECONDARY

STORAGE

The CPU contains circuits that control and execute

instructions by using some type of MEMORY. Memory
is referred to by size, such as 16K, 32K, 64K, and so on.
The "K" represents the value of 1,000. Therefore

16,000 is 16K.

Semiconductor memory consists of hundreds of

thousands of tiny electronic circuits etched on a silicon
chip. Each of these electronic circuits is called a BIT
CELL and can be in either an OFF or ON state to
represent a 0 or 1 bit. This state depends on whether or
not current is flowing in that cell. Another name used
for semiconductor memory chips is integrated circuits
(ICs). Developments in technology have led to
large-scale integration (LSI) that allows more and more
circuits to be squeezed onto the same silicon chip.

Some of the advantages of semiconductor storage

are fast internal processing speeds, high reliability, low

power consumption, high density (many circuits), and
low cost. However, there is a drawback to this type of

storage. It may be VOLATILE, which means it requires
a constant power source. When the power for your
system fails and you have no backup power supply, all

of the stored data is lost.

Primary Storage

Two classifications of primary storage with which

you should become familiar are read-only memory
(ROM) and random-access memory (RAM).

READ-ONLY MEMORY (ROM).--In computers,

it is useful to have instructions that are used often,
permanently stored inside the computer. ROM enables
us to do this without loosing the programs and data
when the computer is powered down. Only the

computer manufacturer can provide these programs in
ROM; once done, you cannot change it. Consequently,
you cannot put any of your own data or programs in
ROM. Many complex functions, such as translators for
high-level languages, and operating systems are placed
in ROM memory.

Since these instructions are hardwired, they can be

performed quickly and accurately. Another advantage
of ROM is that your imaging facility can order
programs tailored for its specific needs and have them
installed permanently in ROM. Such programs are

called microprograms or firmware.

RANDOM-ACCESS MEMORY (RAM).--RAM

is another type of memory found inside computers. It

may be compared to a chalkboard on which you can
scribble down notes, read them, and erase them when
finished. In the computer, RAM is the working
memory. Data can be read (retrieved) or written
(stored) in RAM by providing the computer with an
address location where the data is stored or where you
want it to be stored. When the data is no longer
requited, you may simply write over it. Thus you can
use the storage location again for something else.

Secondary Storage

Secondary storage, or auxiliary storage, is memory

external to the main body of the computer (CPU) where
programs and data can be stored for future use. When
the computer is ready to use these programs, the data is
read into primary storage. Secondary storage media
extends the storage capabilities of the computer system.
Secondary storage is required for two reasons. First, the

working memory of the CPU is limited in size and

cannot always hold the amount of data required.
Second, data and programs in secondary programs do

not disappear when the power is turned off. Secondary
storage is nonvolatile memory. This information is lost
only when you erase it. Magnetic disks are the most
common type of secondary storage. They may be either
floppy disks or hard disks (hard drives).

PERIPHERAL DEVICES

Peripheral devices include all the input and output

devices used with a computer system. When these
devices are under control of the CPU, they are said to
be on line. When they perform their function
independently, not under direct control of the CPU, they

are said to be off line. The following peripheral devices
are used commonly for input and output. Those that

perform only input are marked (I), those that perform
only output are marked (O), and those that perform both
input and output are marked (I/O).

Optical Character Reader (I)

An optical character reader reads printed data

(characters) and translates it to machine code.

Keyboard (I)

The keyboard is used by a computer operator to

communicate with a computer system.

3-4

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> CPU PRIMARY AND SECONDARY STORAGE The CPU contains circuits that control and execute instructions by using some type of MEMORY. Memory is referred to by size, such as 16K, 32K, 64K, and so on. The "K" represents the value of 1,000. Therefore 16,000 is 16K. Semiconductor memory consists of hundreds of thousands of tiny electronic circuits etched on a silicon chip. Each of these electronic circuits is called a BIT CELL and can be in either an OFF or ON state to represent a 0 or 1 bit. This state depends on whether or not current is flowing in that cell. Another name used for semiconductor memory chips is integrated circuits (ICs). Developments in technology have led to large-scale integration (LSI) that allows more and more circuits to be squeezed onto the same silicon chip. Some of the advantages of semiconductor storage are fast internal processing speeds, high reliability, low power consumption, high density (many circuits), and low cost. However, there is a drawback to this type of storage. It may be VOLATILE, which means it requires a constant power source. When the power for your system fails and you have no backup power supply, all of the stored data is lost. Primary Storage Two classifications of primary storage with which you should become familiar are read-only memory (ROM) and random-access memory (RAM). READ-ONLY MEMORY (ROM).--In computers, it is useful to have instructions that are used often, permanently stored inside the computer. ROM enables us to do this without loosing the programs and data when the computer is powered down. Only the computer manufacturer can provide these programs in ROM; once done, you cannot change it. Consequently, you cannot put any of your own data or programs in ROM. Many complex functions, such as translators for high-level languages, and operating systems are placed in ROM memory. Since these instructions are hardwired, they can be performed quickly and accurately. Another advantage of ROM is that your imaging facility can order programs tailored for its specific needs and have them installed permanently in ROM. Such programs are called microprograms or firmware. RANDOM-ACCESS MEMORY (RAM).--RAM is another type of memory found inside computers. It may be compared to a chalkboard on which you can scribble down notes, read them, and erase them when finished. In the computer, RAM is the working memory. Data can be read (retrieved) or written (stored) in RAM by providing the computer with an address location where the data is stored or where you want it to be stored. When the data is no longer requited, you may simply write over it. Thus you can use the storage location again for something else. Secondary Storage Secondary storage, or auxiliary storage, is memory external to the main body of the computer (CPU) where programs and data can be stored for future use. When the computer is ready to use these programs, the data is read into primary storage. Secondary storage media extends the storage capabilities of the computer system. Secondary storage is required for two reasons. First, the working memory of the CPU is limited in size and cannot always hold the amount of data required. Second, data and programs in secondary programs do not disappear when the power is turned off. Secondary storage is nonvolatile memory. This information is lost only when you erase it. Magnetic disks are the most common type of secondary storage. They may be either floppy disks or hard disks (hard drives). PERIPHERAL DEVICES Peripheral devices include all the input and output devices used with a computer system. When these devices are under control of the CPU, they are said to be on line. When they perform their function independently, not under direct control of the CPU, they are said to be off line. The following peripheral devices are used commonly for input and output. Those that perform only input are marked (I), those that perform only output are marked (O), and those that perform both input and output are marked (I/O). Optical Character Reader (I) An optical character reader reads printed data (characters) and translates it to machine code. Keyboard (I) The keyboard is used by a computer operator to communicate with a computer system. 3-4 contents Advanced Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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