2. COMPUTER
Y
our computer looks like a box accompanied by a
screen, keyboard, and mouse, but there’s a lot
hidden inside that box.
3. What’s Inside Your Computer?
What is the system unit?
Box-like case
containing electronic
components used to
process data.
It is the case that holds
the computer’s critical
components.
4. Motherboard
Main circuit board in system unit
Contains the important components
of the computer.
Also called system board
5. The System Unit
What are common components inside the system unit?
power supply
Processor
Memory
Adapter cards
drive bays
Sound card
Video card
processor
ports
memory
Ports
Drive bays
Power supply
video card
sound card
6. A computer with nothing but a processor, memory, and
power supply isn’t very useful because it can’t
communicate with you or with other computers.
Each of the other core components exist to either store information or let the processor
communicate:
✦ Bus — Connects the processor to the memory, I/O channels, and display.
✦ I/O channels — Connects the bus (and therefore the processor) to the disk,
keyboard, mouse, network, and any other devices
✦ Disk — Stores large amounts of information, retaining that information even when
the power is off.
✦ Display — Draws images and characters on a monitor, giving programs a way to
output in a way you can read
7.
8. Processor and Instructions
A special signal inside the computer, called the clock signal
(or just the clock), synchronizes components in the
computer, providing the cadence to which the entire
assembly marches. The clock times every action by the
processor and sets the synchronization requirements for all
the other components.
Every instruction executed by the processor starts on the
beginning of a clock cycle and lasts for one or more clock
cycles.
9. Executing instructions is the work the processor does. The tasks the processor carries out —
tracking actions you take with the keyboard, joystick, or mouse; rendering and presenting
the graphics on the display; moving information from disk to memory and back;
communicating with your network; running your desktop accessories; or keeping the
current print job going — each require some number of instructions to complete. The
number of instructions required divided by the number of instructions per second
determines how long each task takes.
10. Buses
✦ Front side bus — The front side bus (FSB) connects the processor to a
chipset, one or two chips responsible for joining all the different buses
together. The two major processor manufacturers, Intel and AMD, each use
a different design for the FSB. Because of that, you can’t directly plug an Intel
chip into an AMD socket, and vice versa.
✦ Memory bus — The memory bus connects the chipset to the memory
modules.
✦ Graphics bus — All high performance graphics chips interface to the
chipset through an Accelerated Graphics Port (AGP) bus.
✦ Expansion bus — The expansion bus connects adapter cards and I/O
buses to the chipset.
11.
12. Memory
RAM is our working memory storage. All the data, which the PC uses and works with during
operation, are stored here.
13. The memory module operates the individual chips in parallel.
The key parameters defining a memory module are these:
✦ Capacity — A memory module holds a specified number of bytes, with one address
corresponding to each byte. The capacity of a memory module is the number of bytes it holds.
✦ Width — A memory module built from multiple chips in parallel can be as wide as the module
designer wants, with the width being the number of bits (8 to a byte) that the memory accesses
at one time. Common widths for memory modules used in current computers are 32, 36, 64, and
72 bits, depending on whether or not your computer checks data transfers from memory for
reliability.
✦ Access time — There is a minimum interval the memory requires from the time it’s told to read
a number to the time when the number is available for the processor to use. Smaller access
times mean the memory is faster and more expensive, but faster memory does not make your
computer run faster.
✦ Cycle time — Another interval, the cycle time, specifies the minimum time from one memory
operation to the next. The memory requires a small delay for it to recover between when it
transfers data on the bus and when it starts the next operation. The cycle time is the access time
plus that small recovery delay.
14. Hard Disk
is the most popular storage device used to store
various kinds of data in most computers.
is a data storage device used for storing and
retrieving digital information using rapidly rotating
disks. An HDD retains its data even when powered
off. It is the computer’s main storage media device
that permanently stores all data on the computer.
The hard drive was first introduced on September
13, 1956 and consists of one or more hard
drive platters inside of air sealed casing.
15. Aside from its capacity, the important characteristics of a disk all
relate to performance.
The key disk performance characteristics are:
✦ Rotation rate — Rotation rate is the speed at which the disk platters turn under the
heads, measured in revolutions per minute (RPM).
✦ Access time — Access time is how long it takes from when the processor requests data
from the disk until it’s available.
✦ Sustained transfer rate — The data transfer rate a disk can sustain is the rate at which
the combination of disk and I/O channel can, over period of time, maintain a data
transfer.
16.
17. Video cards and Monitors
Monitor
device connected to a computer that displays information on a screen.
Video Card
the electronic components required to generate a video signal that is sent to the video
display through a cable. The video adapter is usually located either on the computer's main
system board or on an expansion board.
18. Pixel
A pixel (short for “picture element”) is one of thousands of tiny spots in a grid on a
display screen or printed sheet. These spots, or blocks, are individually colored in
order to show images on computer screens, and represent the smallest elements
that may be manipulated to create graphics.
19. Resolution
the clarity or fineness of detail attained by a monitor or a printer in producing an
image. In relation to computer monitors, resolution is defined as the number of pixels
per unit of measurement (such as inch or centimeter) on a video display. The word
resolution is commonly used to denote the total number of pixels displayed
horizontally or vertically on the video display.
