Bitwise operators

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Programming C/C++ on Eclipe
Trình bày : Ths HungNM
LOW-LEVEL PROGRAMMING
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Bitwise operators.
Bitwise-Field structure
Other Low-Level Techniques
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Bitwise operators
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Bitwise shift operators
Bitwise component And, Or
Using bitwise operators to access bits
Using bitwise operators to access Bit-Fields
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Bitwise operators
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Bitwise shift operators
Using << (left shift) >> (right shift).
Example :
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Bitwise component
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List the remaining bitwise components.
Symbol
Meaning
~
Bitwise component
&
Bitwise and
^
Bitwise exclusive or
|
Bitwise inclusive or
Example.
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Using bitwise operator to access bits
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Setting a bit
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Example : Setting bit 4 for i;
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Clearing a bit
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Testing a bit
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Using bitwise operator to access Bit-Fields
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Modifying a bit-field.
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Using bitwise and, bitwise or for modifying a bit field.
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Example :
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Retrieving a bit-field
The bit-field at the right end of number (in the least
significant bits),fetching its value easy.
 Example :
 Other you can first shift the bit-field to the end before
extracting the field using & operator.
 Example :

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Bit-Fields in structures
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Using bit-fields we can define a C structure with
identical layout.
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Example :
The number after each member indicate it length
of bit.
The type of bit-field must be either int, unsigned
int, signed int.
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Other Low-Level Techniques
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Defining Machine-Dependent Types
The char type –by definition – occupies one byte, We
sometime treats character as bytes.
 Using theme to store data that’s not necessarily in
character form.
• typedef unsigned char BYTE;
 Depend on the machine x86 architecture make
extensive use of 16 bit words. That you can defines:
• typedef unsigned short WORD;
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Other Low-Level Techniques
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Using pointer as address.
Create a pointer that represents is specific address
easy.
 We just cast an integer into a pointer.
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Example :
BYTE *p;
 p = (BYTE *)0x1000 // p content address 0x1000
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Example : View memory information
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Example : View memory information
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Example : View memory information
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Using gcc test it on an x86 with linux.
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End
• Thank You
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