The system unit contains the main electronic components of a computer including the motherboard, processor, memory, power supply, and storage devices. The processor interprets and executes instructions, containing a control unit that directs operations and an arithmetic logic unit that performs calculations. Processors contain registers for temporary storage and operate through a machine cycle of fetch, decode, execute, and store steps. Memory temporarily stores instructions, data, and results and can be volatile RAM or non-volatile ROM/flash. Storage such as hard disks provides permanent non-volatile storage of data on platters accessed by read/write heads.

1. 1
Introduction to Computers and
Programming (CSC103)
Lecture 02

2. The System Unit
• The system unit is a case that contains electronic
components of the computer used to process data
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3. The System Unit
• The inside of the system unit on a desktop
personal computer includes:
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Drive bay(s)
Power supply
Sound card
Video card
Processor
Memory

4. The System Unit
• The motherboard is the main circuit board of the
system unit
– A computer chip contains integrated circuits (IC)
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5. Processor
• The processor, also called the central processing
unit (CPU), interprets and carries out the basic
instructions that operate a computer
– Contain a Control Unit and an Arithmetic Logic Unit
(ALU)
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6. Processor
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7. Processor
• The control unit is the component of the
processor that directs and coordinates most of
the operations in the computer
– Interprets each instruction issued by a program and
then initiates the appropriate action (to carry out the
instruction)
• The arithmetic logic unit (ALU) performs
arithmetic, comparison, and other operations
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8. Processor – Machine Cycle
• For every instruction, a processor repeats a set of
four basic operations, which comprise a machine
cycle
1. Fetch
2. Decode
3. Execute
4. Store
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9. Processor
The processor contains registers, that temporarily hold data
and instructions
• Registers are part of the Processor
• Processor has many different type of registers
• Register function includes; storing location, storing instruction, storing data
and storing results of a calculation
The system clock controls the timing of all computer operations
• The pace of the system clock is called the clock speed, and is measured in
gigahertz (GHz)
• Giga = Billion, Hertz = one cycle per second
• Faster the clock speed, more instructions can be executed per second
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10. Dual Core and Multi-Core Processors
• Dual-Core Processor is a single
chip that contains two separate
processors
• Multi-Core Processor is a chip
with two or more separate
processors
– Implements multiprocessing into a
single physical package
– Quad-Core Processor contains four
(4) cores 10

11. Moore’s Law
• Number of transistors and resistors placed on
computer chips would double every year
– With a proportional increase in computing power and
decrease in cost
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12. 12
Figure: Moore’s Law

13. Processor
• A processor chip
generates heat that could
cause the chip to burn up
• Require additional cooling
– Heat sinks
– Liquid cooling technology
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14. Memory
• Memory consists of electronic components that
store instructions waiting to be executed by the
processor, data needed by those instructions, and
the results of processing the data
• Stores three basic categories of items:
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The operating
system and other
system software
Application
programs
Data being
processed and the
resulting
information

15. Memory
• Each location in memory has an address
• Byte is the basic storage unit in memory
• Memory size is measured in kilobytes (KB or K),
megabytes (MB), gigabytes (GB), or terabytes (TB)
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16. Memory
• The system unit contains two types of memory:
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Volatile memory
Loses its contents when
power is turned off
Example includes RAM
Nonvolatile memory
Does not lose contents
when power is removed
Examples include ROM,
flash memory, and
CMOS

17. Memory – RAM
• RAM (Random Access Memory) is also called main
memory
• Consists of memory chips that can be read from
and written to by the processor and other devices
• When you turn on computer
– Certain Operating System files are loaded into RAM
from a storage device such as a hard disk
• Saving is the process of copying data, instructions
and information from RAM to a storage device
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18. Storage
Storage holds data, instructions, and
information for future use
A storage medium is the physical
material on which a computer keeps
data, instructions, and information
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19. Storage
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20. Storage
• Capacity is the number of bytes a storage medium
can hold
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21. Storage
• A storage device is the computer hardware that
records and/or retrieves items to and from
storage media
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Reading is the process
of transferring items
from a storage medium
into memory
Writing is the process of
transferring items from
memory to a storage
medium

22. Storage
• Access time measures:
– The amount of time it takes
a storage device to locate an
item on a storage medium
• In milliseconds or
microseconds
• Measured in KBps and MBps
– The time required to deliver
an item from memory to the
processor
• In nanoseconds
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23. Hard Disks
• A hard disk contains one or more inflexible, circular platters
that use magnetic particles to store data, instructions, and
information
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24. Hard Disks
• Characteristics of a hard disk
include:
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Capacity Platters
Read/Write
Heads
Cylinders
Sectors and
Tracks
Revolutions
per Minute
Transfer Rate Access Time

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26. Hard Disks
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27. Hard Disks
• The hard disk arms
move the read/write
head, which reads items
and writes items in the
drive
– Location often is
referred to by its
cylinder
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28. Hard Disks
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