Багшийн өгсөн эхний орчуулах текст шүү
TEXT 1. “HARDWARE”
( Reading - 1 )
The functions of the hardware composing a computer can be
divided broadly into the following five categories: Input; Storage; Operation; Control and Output.
The following are the units that implement the
above-mentioned functions:
· Input unit: This unit inputs the data and programs
for computer processing. It is equivalent to the human eyes and ears.
· Storage unit: This unit stores the input data
and programs. It is equivalent to the memory section of the human brain.
· Arithmetic unit: This unit conducts calculation
and decision on the stored data according to the instructions of the program.
It is equivalent to the thinking section of the human brain.
· Control unit: This unit controls the input unit,
storage unit, arithmetic unit and the output unit. It is equivalent to the
human central nervous system.
· Output unit: This unit outputs the results of
computer processing in a format that can be understood by humans. It is
equivalent to the human hands and mouth.
These five units are called the "computer five main
units".
Since the control unit and the arithmetic
unit are handled as one unit, they are called the processor (processing
unit) or central processing unit (CPU). The general term "peripheral
devices" is used to refer to the input unit, the output unit and
the auxiliary storage devices that are outside the processor and exchange data
with the main storage unit.
Likewise, the storage units are divided into main
storage unit and auxiliary storage device, depending on their functions.
(1) RAM (Random Access Memory)
The RAM is semiconductor memory in which data
writing and reading is possible. When the computer is turned off, the stored
data is lost. This property is called volatility. Since most main storage units
are composed of RAMs, the processor can be made to read and write information
from the main storage unit at random by specifying the address.
RAMs are classified into DRAMs and SRAMs.
1)DRAM (Dynamic RAM)
A DRAM represents bits, and stores information
depending on whether the part called capacitor is being charged (status
"1") or is not being charged (status "0").
Since the circuits are simple and small, RAMs of large
capacity can be created at low cost. However, since the charge stored in the
capacitor is lost after a lapse of time, the memory needs to be rewritten
(recharged) at regular intervals. This operation is called refreshing. Once,
DRAMs were used in the main storage unit, but currently they are also used in
storage units, etc., contained in the input/output units of printers and other
devices.
2)SDRAM
(Synchronous DRAM)
Due to the progress of IC technology, and the consequent
substantial improvement of the performance of processors, the operating speed
of the DRAMs that composed the storage unit could not keep up with the
operating speed of the processors. For that reason, an external clock signal
that indicates the processor operation timing is now set in the DRAM and
through synchronization with this signal, complicated address specifications
are reduced and simplified, enabling the development of DRAMs that operate at
high speeds. These types of DRAMs are called synchronous DRAMs (SDRAM).
3)SRAM (Static RAM)
SRAMs are created with a circuit called the flip-flop.
The flip-flop settles the output according to the previous input and the
current input, and can preserve the status "1" and "0"
inside the circuit. Since data is not lost unless the computer is turned off,
memory refreshing is not necessary. However, since SRAM circuits are
complicated, the memory capacity is smaller than that of DRAMs and the cost is
higher. However, since its processing speed is high, it is used in devices such
as the registers contained in main storage units and processors.
(2) ROM (Read Only Memory)
The ROM is semiconductor memory for read use only.
Since programs and data are stored in the ROM from the beginning, the stored
information is not lost even if the computer is turned off. This property is
called nonvolatility.
ROMs are classified into mask ROMs and user programmable ROMs.
1)Mask
ROM
Since programs and data are already written in the Mask
ROM before it is shipped by the manufacturer, the user cannot add any
programs or data. Mask ROMs are used in the memories of game cassettes and IPL
(Initial Program Loader), a program used to start the computer, etc.
2)User programmable ROM
The user programmable ROM is a type of ROM, but since
at the time it is shipped by the manufacturer it has nothing stored in it, the
user can write data into it once. The following types of user programmable ROM
exist
· PROM (Programmable ROM): Once data
has been written, it cannot be erased.
· EPROM (Erasable PROM): It can be
erased with ultraviolet light and rewritten.
· EEPROM (Electrically Erasable PROM):
It can be erased through the application of electrical voltage and rewritten.
EEPROM is used in a storage medium called flash memory,
which is used in the registration of image data of digital cameras, etc.
Likewise, it is also used in the storage section of IC cards, etc.
