Transcript PowerPoint

Computer Applications
NCBS Stage 1
Course Content and
Assessment
• Practical – 60% (2 Hrs Weekly)
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File Management
Internet
Word Processing
Spreadsheets
• Theory – 40% (I Hr Weekly)
The Central Processing Unit
Slide 2
Computer Applications Stage 1
The Central Processing
Unit
• The ‘brain’ of the computer
• A tiny piece of silicon (chip)
containing millions of transistors
• Getting smaller, faster and
cheaper all the time
The Central Processing Unit
Slide 3
Computer Applications Stage 1
Functions of a Computer
• The function of a computer is to
process data
• Processing means turning data into
meaningful information
Input (Data in)
Processing
(Calculations
etc)
Output
(Results of
processing –
Information)
Storage of
Results
The Central Processing Unit
Slide 4
Computer Applications Stage 1
Input
• Data
– Raw data is figures etc that can be
manipulated
• Programs
– Instructions to the computer about
what to do with the data
The Central Processing Unit
Slide 5
Computer Applications Stage 1
Input devices
• Used to put data and
programs into the computer
– keyboard, disk, microphone,
scanner etc
The Central Processing Unit
Slide 6
Computer Applications Stage 1
Processing
Means turning raw data into
meaningful information
Logical Operations
Mathematical
Operations
A=6
B=4
1+1=2
Logical deduction
A>B
The Central Processing Unit
Slide 7
Computer Applications Stage 1
Processing
• Takes place in the CPU
• Main Memory holds the
data and instructions
that are being used
• Processing needs both
the CPU and Memory
The Central Processing Unit
Slide 8
CPU
Memory
Computer Applications Stage 1
Output
•
The results of processing
need to be output for user
to see and use
The Central Processing Unit
Slide 9
Computer Applications Stage 1
Output can be sent to ….
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Screen
Disk (floppy, zip, CD, DVD etc)
Printer
To another computer via a
network
The Central Processing Unit
Slide 10
Computer Applications Stage 1
The Parts of the CPU
These parts make up the CPU
Control
Unit
ALU
Registers
The Central Processing Unit
Slide 11
• Control unit
• Arithmetic/Logic
Unit
• Registers
Computer Applications Stage 1
The Control Unit
• This controls everything that
happens inside the computer
• It transfers data and program
instructions between the Memory
and the ALU
• It sends the results back to
Memory and later to a storage
device
The Central Processing Unit
Slide 12
Computer Applications Stage 1
The Arithmetic/Logic
Unit (ALU)…
• Performs either mathematical or
logical operations
– Addition, subtraction,
multiplication etc
– Greater than, less than etc
• The ALU produces results
The Central Processing Unit
Slide 13
Computer Applications Stage 1
Registers…
• Are temporary storage areas for
data and/or instructions
• Data, instructions and results
are held in registers for a very
short time
• They are faster than RAM so
they speed up processing
• Areas in the ALU and CU
The Central Processing Unit
Slide 14
Computer Applications Stage 1
Main Memory
• Main Memory is made
up of RAM and ROM
and is not part of the
CPU
• Data passes in and
out of RAM to be
processed
The Central Processing Unit
Slide 15
CPU
Memory
Computer Applications Stage 1
Storage
• Anything stored in RAM is only held
there temporarily - until processing
is complete
• Permanent storage is called
Secondary Storage
• This is needed or work would be lost
as soon as the computer was
switched off
The Central Processing Unit
Slide 16
Computer Applications Stage 1
Storage Devices
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The Central Processing Unit
Disks
CDs
DVDs
Paper
Slide 17
Computer Applications Stage 1
Memory v Storage
• Memory or Main Memory is the term
used for temporary storage ie RAM
and is outside the CPU
• Registers are a type of Main
Memory found in the CPU
• Secondary storage covers a lot of
devices used for files such as disks,
CDs etc
The Central Processing Unit
Slide 18
Computer Applications Stage 1
Programs
• Programs are sets of instructions
for the computer to follow
• The program must be in Memory
(RAM) before processing can take
place
The Central Processing Unit
Slide 19
Computer Applications Stage 1
Executing/Running a
Program
The program must be placed in
Main Memory
The data must be placed in Main
Memory
The Central Processing Unit
Slide 20
Computer Applications Stage 1
Running a Program
Once the program and data are in
place the following sequence is
followed:
1.
2.
3.
4.
Fetching
Decoding
Executing
Storing
The Central Processing Unit
Slide 21
CPU
Memory
Computer Applications Stage 1
Fetching Instructions
CONTROL
UNIT
ALU
Registers
The control unit
fetches (gets)
the instruction
from memory.
Memory
The Central Processing Unit
Slide 22
Computer Applications Stage 1
Decoding Instructions
• The control unit
decodes the
instruction
• It then moves the
necessary data
from Memory to
the ALU for
processing
The Central Processing Unit
Slide 23
CONTROL
UNIT
ALU
Registers
Memory
Computer Applications Stage 1
Executing
Arithmetic/Logic Operations
The ALU performs the
arithmetic or logical
operation on the data
All processing takes place in
the ALU
The Central Processing Unit
Slide 24
Computer Applications Stage 1
Storing Results
The ALU stores
the result of its
operation on the
data in Memory or
in a Register until
they are output to
a storage device
The Central Processing Unit
Slide 25
Control
Unit
ALU
Registers
MEMORY
Computer Applications Stage 1
The Machine Cycle
• This is the time taken by the CPU to
process a single program instruction
• The time is divided into 2 phases
– I-time and
– E-time
The Central Processing Unit
Slide 26
Computer Applications Stage 1
(I-time) Instruction
Time
The time it takes the Control Unit to
fetch an instruction from Memory and
decode it is called instruction time
Control
Unit
+
ALU
Memory
Memory
The Central Processing Unit
Control
Unit
Slide 27
Computer Applications Stage 1
(E-time) Execution Time
The time it takes to carry out an ALU
operation and then store the result
is called execution time
ALU
ALU
+
The Central Processing Unit
Slide 28
Registers
Memory
Computer Applications Stage 1
Computer Speed
• Computers carry out millions of
instructions per second (MIPS)
• Processors are described in
MegaHertz (MHz) and GigaHertz
(GHz)
• These figures indicate how quickly
the computer can process
instructions
The Central Processing Unit
Slide 29
Computer Applications Stage 1
Conclusion and Key
Words
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CPU
ALU
Registers
Control Unit
Main Memory
RAM
Data
The Central Processing Unit
• Information
• Program
• Secondary
storage
• Machine Cycle
• I-time
• E-time
Slide 30
Computer Applications Stage 1
References
Computing Essentials 2005
By Timothy and Linda O’Leary
Computers - Tools for an Information
Age
By H L Capron - Ch 3
Computing in the Information Age
By Stern and Stern - Ch 4
The Central Processing Unit
Slide 31
Computer Applications Stage 1