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51
Digital Computers
There are two fundamentally different types of computers: analog and digital. In current usage
"computer" usually refers to high speed digital computers. These computers are playing an increasing
role in all branches of the economy. Digital computers are based on manipulating discrete binary digits
(Is and Os). They are generally more effective than analog computers for four principal reasons: they
are faster: they are not so susceptible to signal interference; they can transfer huge data bases more
accurately; and their coded binary data are easier to store and retrieve than the analog signals. For all their
apparent complexity, digital computers are considered lo be simple machines. Digital computers are
able lo recognize only two states in each of its millions of switches, "on" or "off", or high voltage or low
voltage. By assigning binary numbers to these states 1 for "on" and 0 for "off", and linking many
switches together, a computer can represent any type of data from numbers lo letters and musical notes.
It is this process of recognizing signals that is known as digitization. The real power of a computer
depends on the speed with which it checks switches per second. The more switches a computer checks in
each cycle, the more data it can recognize at one time and the faster it can operate, each switch being
called a binary digit or bit. A digital computer is a complex system of four functionally different elements:
1) the central processing unit (CPU). 2) input devices. 3) memory-storage devices called disk drives, 4)
output devices. These physical parts and all their physical components are called hardware.
The central processing unit is the heart of a computer. In addition to performing arithmetic and logic
operations on data, it controls the rest of the system. Sometimes the CPU consists of several
linked microchips, each performing a separate task, but most computers require only a single
microchip as the CPU.
Input devices let users enter commands, data, or programs for processing by the CPU. Information
typed at the computer keyboard, which is much like typewriter, is translated into a series of binary
numbers the CPU can manipulate. The mouse is another widely used mechanical input device to move
the cursor on the display screen, the user moves the mouse, selects operations and activates
commands on the screen by pressing buttons on the top of the mouse. The power of computers greatly
depends on the characteristics of memory-storage devices.
Most digital computers store data both internally in what is called mam memory, and externally, on auxiliary
storage units. As a computer processes data and instructions, it temporary stores information
internally on special memory microchips. Auxiliary storage units supplement the main memory when
programmes are too large and they also offer a more reliable method for storing data. There exist
different kinds of auxiliary storage devices removable magnetic disks being the most widely used.
They can store up to 100 megabytes of data on one disk, a byte being known as the basic unit of data
storage.
Output devices let the user see the results of the computer's data processing. Being the most
commonly used output device, the monitor accepts video signals from a computer and shows different
kinds of information such as texts, formulas and graphics on its screen. With the help of various printers
information stored in one of the computer's memory systems can be easily printed on paper in a
desired number of copies.
Programmes, also called software, are detailed sequences of instructions that direct the computer
hardware to perform useful operations. Due to a computer's operating system hardware and software
systems can work simultaneously. An operating system consists of a number of programmes
coordinating operations, translating the data from different input and output devices, regulating data
storage in memory, transferring tasks to different processors and functions that help programmers to
write software. In large corporations software is often written by groups of experienced programmers
each person focusing on a specific aspect of the total project. For this reason scientific and industrial
software sometimes costs much more
than the computers on which the programmes run.
Digital Computers
There are two fundamentally different types of computers: analog and digital. In current usage
"computer" usually refers to high speed digital computers. These computers are playing an increasing
role in all branches of the economy. Digital computers are based on manipulating discrete binary digits
( I s and Os). They are generally more effective than analog computers for four principal reasons: they
are faster: they are not so susceptible to signal interference; they can transfer huge data bases more
accurately; and their coded binary data are easier to store and retrieve than the analog signals. For all their
apparent complexity, digital computers are considered lo be simple machines. Digital computers are
able lo recognize only two states in each of its millions of switches, "on" or "off", or high voltage or low
voltage. By assigning binary numbers to these states 1 for "on" and 0 for "off", and linking many
switches together, a computer can represent any type of data from numbers lo letters and musical notes.
It is this process of recognizing signals that is known as digitization. The real power of a computer
depends on the speed with which it checks switches per second. The more switches a computer checks in
each cycle, the more data it can recognize at one time and the faster it can operate, each switch being
called a binary digit or bit. A digital computer is a complex system of four functionally different elements:
1) the central processing unit (CPU). 2) input devices. 3) memory-storage devices called disk drives, 4)
output devices. These physical parts and all their physical components are called hardware.
The central processing unit is the heart of a computer. In addition to performing arithmetic and logic
operations on data, it controls the rest of the system. Sometimes the CPU consists of several
linked microchips, each performing a separate task, but most computers require only a single
microchip as the CPU.
Input devices let us ers enter commands, data, or programs for processing by the CPU. Information
typed at the computer keyboard, which is much like typewriter, is translated into a series of binary
numbers the CPU can manipulate. The mouse is another widely used mechanical input device to move
the cursor on the display screen, the user moves the mouse, selects operations and activates
commands on the screen by pressing buttons on the top of the mouse. The power of computers greatly
depends on the characteristics of memory-storage devices.
Most digital computers store data both internally in what is called mam memory, and externally, on auxiliary
storage units. As a computer processes data and instructions, it temporary stores information
internally on special memory microchips. Auxiliary storage units supplement the main memory when
programmes are too large and they also offer a more reliable method for storing data. There exist
different kinds of auxiliary storage devices removable magnetic disks being the most widely used.
They can store up to 100 megabytes of data on one disk, a byte being known as the basic unit of data
storage.
Output devices let the user see the results of the computer's data processing. Being the most
commonly used output device, the monitor accepts video signals from a computer and shows different
kinds of information such as texts, formulas and graphics on its screen. With the help of various printers
information stored in one of the computer's memory systems can be easily printed on paper in a
desired number of copies.
Programmes, also called software, are detailed sequences of instructions that direct the computer
hardware to perform useful operations. Due to a computer's operating system hardware and software
systems can work simultaneously. An operating system consists of a number of programmes
coordinating operations, translating the data from different input and output devices, regulating data
storage in memory, transferring tasks to different processors and functions that help programmers to
write software. In large corporations software is often written by groups of experienced programmers
each person focusing on a specific aspect of the total project. For this reason scientific and industrial
software sometimes costs much more than the computers on which the programmes run.
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