# Computer Science 101 - PowerPoint PPT Presentation

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## Computer Science 101

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### Computer Science 101 Computer Systems Organization BINARY STORAGE Pappaw, our puter broke. What s a man to do? Perfectly clear, huh? Von Neumann Architecture Basic ... – PowerPoint PPT presentation

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Title: Computer Science 101

1
Computer Science 101
• Computer Systems
• Organization
• BINARY STORAGE

2
Pappaw, our puter broke.
3
Whats a man to do?
Perfectly clear, huh?
4
Von Neumann Architecture
• Basic Architecture of most computers
• Four Major Subunits
• Memory
• Input-output
• Arithmetic-logic unit (ALU)
• Control Unit
• Stored Programs

5
Von Neumann Architecture
• Execution Cycle
• Fetch Instruction
• Decode
• Execute

Processor speed 2.8GHz
giga- G 109 ? 10243 230
1,073,741,824 Hz- cycle per second 2.8 billion
cycles per second
6
Major Components
7
Memory (and other storage devices)
• Stores Numbers, text, programs, addresses,
graphics, sound, video, etc. that are currently
in use. Everything coded in some binary format.
• Divided into fixed size cells (fixed number of
bits).
• This size is commonly 8 bits, and this 8-bit unit
is called a byte.

Memory 3GB DDR3 SDRAM Hard drive 500GB5
8
A bit is what the dentist uses to fix your byte?
9
• Each cell has an address, an unsigned integer.
• All accesses to memory are via a specific address

0
1
2
3
10
Capacity of a Byte
• A byte contains 8 bits. How many different values
can we store in a byte? 00000000
0 00000001 1 00000010
2 . . . 11111111
255 so there are 256 different values.
• In general, there are 2n ways to arrange bits.

11
Capacity of a Byte
• In working with popular software packages, you
may have encountered situations where you were to
choose values for a property, and the range of
values was 0 to 255. Now you can see that the
reason was that the value was being stored in a
byte and that dictates the range.

12
Powerpoint
13
Basic Memory Operations
• Memory Fetch
• Given a specific memory address.
• Retrieve the content stored at that address.
• Memory Store
• Given a specific memory address and
• a specific value,
• store the given value in the cell with the

14
Memory Fetch
2002
2003
2004
2005
15
Memory Fetch
2002
2003
2004
2005
16
Memory Fetch
2002
2003
2004
2005
17
Memory Fetch
2002
2003
2004
2005
18
Memory Fetch
2002
2003
2004
2005
19
Memory Store
20
Memory Store
2002
2003
2004
2005
Given Address 2004 Given Value 10101010
21
Memory Store
2002
2003
2004
2005
Given Address 2004 Given Value 10101010
22
Memory Store
2002
2003
2004
2005
Given Address 2004 Given Value 10101010
23
Memory Store
2002
2003
2004
2005
Given Address 2004 Given Value 10101010
24
Memory Facts and Terminology
• A cell is the minimum unit of access.
• Access time is same for all cells - Random Access
Memory or RAM (nanoseconds - billionths of
second)
• ROM - Read only Memory (fetch but not store)
• Some data items require more than one cell. For
example, an instruction might need four cells.
Note ints require 4 cells (bytes)

25
Terminology
• Storage capacity
• K ? 210 1024 ? Kilo as in Kb
• M ? 220 1,048,576 ? Mega as in Mb
• G ? 230 1,073,741,824 ? Giga as in Gb
• Speed
• 1 ? 1 microsecond 1 millionth of second
• 1 ms 1 millisecond 1 thousandth of second
• 1 ns 1 nanosecond 1 billionth of second
• Cycle rate Hertz is cycle per second

26
We have brown ones, black ones, white ones,
spotted, .