116 lines
5.6 KiB
Plaintext
116 lines
5.6 KiB
Plaintext
HARDWARE:
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CENTRAL PROCESSOR UNIT (CPU): Heart of the PC - it contains
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the microprocessor. The CPU is a set of miniaturized circuits that
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does all the "thinking". It controls the interpretation
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(arithmetic-logic unit) and execution (control unit) of instructions.
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It is this CPU in conjunction with RAM that comprise the computer's
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"brain". The CPU does the "thinking/calculating" while RAM contains
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the instructions or "memories". It is the CPU that largely determines
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the operating speed of the computer.
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BIT: Smallest unit of information recognized by the
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computer. BIT is short for Binary Digit. A Binary Digit can
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be either a 0 or a 1. Several bits make up a byte.
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BYTE: A group of 8 BITS. This grouping of adjacent binary
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digits (bits) is operated on by the computer as a unit.
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Computers use 1 BYTE to represent 1 character such as a
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letter of the alphabet, a number, a punctuation mark, a
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space, etc. A BYTE is also a unit of measure since it
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represents 1 character. For example, when the letter "A" is
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pressed, the keyboard actually sends the following to RAM:
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10000001 - a set of 8 bits. See RAM, FLOPPY DISK.
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RANDOM ACCESS MEMORY (RAM): A set of miniaturized circuits which
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represents the working memory of the computer. This is where
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application programs (software) can be loaded from the outside and then
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executed. The larger the RAM the better. A typical single-user
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computer system may contain approximately 640,000 bytes of RAM. (This is
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often abbreviated as 640k RAM: 1 k bytes is actually = 1024 bytes)
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The RAM is emptied when the computer is turned off - thus it is
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often called "volatile" memory. WHAT YOU SEE ON YOUR COMPUTER MONITOR
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IS ACTUALLY IN RAM ONLY - a temporary storage location. To make it
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permanent we "save" it, or "write" it to a floppy disk or hard drive.
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These devices are not volatile storage - they do not require
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electricity.
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READ ONLY MEMORY (ROM): This is a special section of memory
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that contains instructions which are activated each time the
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computer is turned on. These instructions are set at the
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factory and cannot be changed - thus, they can only be "read"
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not written to. ROM instructions perform equipment checks
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and initialization of the computer prior to each use.
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DISK DRIVE: The port in which a floppy disk is inserted. Device that "reads"
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data from a magnetic disk and copies it into the computer's memory (RAM) so it
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can be used by the computer, and that "writes" data from the computer's memory
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onto a disk so it can be stored for later use. Each Disk Drive is labeled
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A,B,C,etc because we often must tell the computer which drive has the disk
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with the information or where to send the information. A Disk Drive reads and
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writes on a 5.25 inch or 3.5 inch floppy disk.
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FLOPPY DISKS: The most commonly used mass storage device. Allows
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entering programs to RAM and saving data from RAM. Will hold data even
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after the computer is turned off. Data on these disks is stored in
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concentric rings called tracks. The Disk surface is a thin piece of
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mylar and is coated with a magnetized material similar to audio or
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video tape.
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The read/write heads can magnetize and demagnetize the coated surface
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repeatedly. Therefore, the Disk can be used, erased, and reused
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indefinitely. An IBM PC disk holds approximately 360k worth of
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information (250 double-spaced pages of text). This is called a
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Double-sided, Double-density Diskette. Newer, smaller 3.5 inch disk
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exist which hold at least twice as much - 720k.
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FIXED DISK DRIVE: Usually named disk drive C. It is essentially a
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very large floppy disk. This Fixed Disk (commonly called a Hard Drive)
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is secured within the machine and cannot be seen or transported. The
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storage capacity is so large it is measured in megabytes (1M = 1K
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squared = 1,048,576 bytes). Fixed Disks are available from 5M on up.
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The advantage is that it is enough space to meet most users' total
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storage needs, operates much faster than a floppy (5-10x faster), and is less
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likely to fail since it lives within the protected computer.
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KEYBOARD: Input device that lets you enter data into the
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computer. The layout is similar to the standard QWERTY
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typewriter keyboard, however there are many extra special
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keys that are defined by the software you are running.
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MONITOR: A television-like device that the computer uses to
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communicate with you. Typically the monitor displays 80
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columns (characters) by 25 rows (lines) of information.
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PRINTER: Most users get at least one Printer for their
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computer. It produces a "Hard-Copy" output of your data
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rather than just being able to view it on the monitor. Dot-
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Matrix printers are inexpensive and fast and can draw
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graphics. Letter-Quality printers are more expensive and
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slower but create pages better than typewritten (even
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pressure on each keystroke).
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MODEM: Short for Modulator/Demodulator. A device to send
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and receive computer output over telephone lines.
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ÚÄÄÄÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄ¿
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³KEYBOARD ³ ÚÄÄÄÄÄ¿ ³MONITOR³
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³Mouse ÃÄÄÄÄ INPUT ÄÄÄÄ>³ CPU ÃÄÄÄÄÄ OUTPUT ÄÄ>³Printer³
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³Light Pen ³ ³ RAM ³ ³Plotter³
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³Microphone³ ÀÄÄÂÄÄÙ ³Speaker³
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³Joystick ³ ³ INPUT ÀÄÄÄÄÄÄÄÙ
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ÀÄÄÄÄÄÄÄÄÄÄÙ ³ and/or
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³ OUTPUT
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ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÁÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿
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³ DISK STORAGE, Tape Storage, Modem, Fixed Disk Storage ³
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ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
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***** END OF FILE: Press <ESC> to return to Main Menu *****
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