Advanced Photography Course

electrical, electronic, and magnetic devices within the
computer itself and all related PERIPHERAL devices.
The peripheral devices consist of items, such as a
keyboard, magnetic tape unit, mouse, scanner, printer,
and so on. The software items are programs and

operating aids written so the computer can process data.
The manufacturer supplies much of the initial software

for a particular computer. This software is known as
SYSTEMS SOFTWARE. Systems software is
designed for broad general use. Examples of systems
software are DOS (disk operating system) for IBM

compatible computers and System 7 for Apple
computers. Software designed to meet a specific
requirement or purpose is called APPLICATION

SOFTWARE. Examples of application software are

WordPerfect, Lotus 1-2-3, and Adobe Photoshop.

FUNCTIONAL UNITS OF A
COMPUTER SYSTEM

Digital computer systems consist of three distinct

units. These units are as follows:

Input unit

Central Processing unit

Output unit

These units are interconnected by electrical cables

to permit communication between them. This allows
the computer to function as a system.

Input Unit

A computer must receive both data and program

statements to function properly and be able to solve
problems. The method of feeding data and programs to
a computer is accomplished by an input device.
Computer input devices read data from a source, such
as magnetic disks, and translate that data into electronic
impulses for transfer into the CPU. Some typical input
devices are a keyboard, a mouse, or a scanner.

Central Processing Unit

The brain of a computer system is the central

processing unit (CPU). The CPU processes data
transferred to it from one of the various input devices.

It then transfers either an intermediate or final result of
the CPU to one or more output devices. A central
control section and work areas are required to perform
calculations or manipulate data. The CPU is the

computing center of the system. It consists of a control

section, an arithmetic-logic section (fig. 3-1), and an

internal storage section (main memory). Each section
within the CPU serves a specific function and has a
particular relationship with the other sections within the
CPU.

CONTROL SECTION.--The control section

directs the flow of traffic (operations) and data. It also

maintains order within the computer. The flow of
control is indicated by dotted arrows in figure 3-1. The
control section selects one program statement at a time
from the program storage area, interprets the statement,
and sends the appropriate electronic impulses to the
arithmetic-logic and storage sections so they can carry

out the instructions. The control section does not
perform actual processing operations on the data. The
control section instructs the input device on when to

start and stop transferring data to the input storage area.
It also tells the output device when to start and stop
receiving data from the output storage area.

ARITHMETIC-LOGIC SECTION.--The

arithmetic-logic section performs arithmetic

operations, such as addition, subtraction,

multiplication, and division. Through internal logic
capability, it tests various conditions encountered
during processing and takes action based on the result.

As indicated by the solid arrows in figure 3-1, data flows

between the arithmetic-logic section and the internal
storage section during processing. Specifically, data is
transferred as needed from the storage section to the
arithmetic-logic section, processed, and returned to
internal storage. At no time does processing take place
in the storage section. Data maybe transferred back and
forth between these two sections several times before
processing is completed. The results are then
transferred from internal storage to an output device, as
indicated by the solid arrow in figure 3-1.

INTERNAL STORAGE SECTION.--The internal

storage section is sometimes called primary storage,
main storage, or main memory, because this section
functions similar to our own human memory.

The storage section serves four purposes; three

relate to retention (holding) of data during processing.
First, as indicated by the solid arrow (fig. 3-1), data is
transferred from an input device to the INPUT
STORAGE AREA where it remains until the computer
is ready to process it. Second, a WORKING
STORAGE AREA ("scratch pad" memory) within the
storage section holds both the data being processed and
the intermediate results of the arithmetic-logic
operations. Third, the storage section retains the

3-2

contents

Advanced Photography Course

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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 -> electrical, electronic, and magnetic devices within the computer itself and all related PERIPHERAL devices. The peripheral devices consist of items, such as a keyboard, magnetic tape unit, mouse, scanner, printer, and so on. The software items are programs and operating aids written so the computer can process data. The manufacturer supplies much of the initial software for a particular computer. This software is known as SYSTEMS SOFTWARE. Systems software is designed for broad general use. Examples of systems software are DOS (disk operating system) for IBM compatible computers and System 7 for Apple computers. Software designed to meet a specific requirement or purpose is called APPLICATION SOFTWARE. Examples of application software are WordPerfect, Lotus 1-2-3, and Adobe Photoshop. FUNCTIONAL UNITS OF A COMPUTER SYSTEM Digital computer systems consist of three distinct units. These units are as follows: Input unit Central Processing unit Output unit These units are interconnected by electrical cables to permit communication between them. This allows the computer to function as a system. Input Unit A computer must receive both data and program statements to function properly and be able to solve problems. The method of feeding data and programs to a computer is accomplished by an input device. Computer input devices read data from a source, such as magnetic disks, and translate that data into electronic impulses for transfer into the CPU. Some typical input devices are a keyboard, a mouse, or a scanner. Central Processing Unit The brain of a computer system is the central processing unit (CPU). The CPU processes data transferred to it from one of the various input devices. It then transfers either an intermediate or final result of the CPU to one or more output devices. A central control section and work areas are required to perform calculations or manipulate data. The CPU is the computing center of the system. It consists of a control section, an arithmetic-logic section (fig. 3-1), and an internal storage section (main memory). Each section within the CPU serves a specific function and has a particular relationship with the other sections within the CPU. CONTROL SECTION.--The control section directs the flow of traffic (operations) and data. It also maintains order within the computer. The flow of control is indicated by dotted arrows in figure 3-1. The control section selects one program statement at a time from the program storage area, interprets the statement, and sends the appropriate electronic impulses to the arithmetic-logic and storage sections so they can carry out the instructions. The control section does not perform actual processing operations on the data. The control section instructs the input device on when to start and stop transferring data to the input storage area. It also tells the output device when to start and stop receiving data from the output storage area. ARITHMETIC-LOGIC SECTION.--The arithmetic-logic section performs arithmetic operations, such as addition, subtraction, multiplication, and division. Through internal logic capability, it tests various conditions encountered during processing and takes action based on the result. As indicated by the solid arrows in figure 3-1, data flows between the arithmetic-logic section and the internal storage section during processing. Specifically, data is transferred as needed from the storage section to the arithmetic-logic section, processed, and returned to internal storage. At no time does processing take place in the storage section. Data maybe transferred back and forth between these two sections several times before processing is completed. The results are then transferred from internal storage to an output device, as indicated by the solid arrow in figure 3-1. INTERNAL STORAGE SECTION.--The internal storage section is sometimes called primary storage, main storage, or main memory, because this section functions similar to our own human memory. The storage section serves four purposes; three relate to retention (holding) of data during processing. First, as indicated by the solid arrow (fig. 3-1), data is transferred from an input device to the INPUT STORAGE AREA where it remains until the computer is ready to process it. Second, a WORKING STORAGE AREA ("scratch pad" memory) within the storage section holds both the data being processed and the intermediate results of the arithmetic-logic operations. Third, the storage section retains the 3-2 contents Advanced Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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