- Bit patterns is a
royal pain to write using
decimal representation
It is a lot easier to write bit patterns using the Binary Number System
- C provides you with
different number systems to
write
bit patterns with more ease !
- Denoting binary numbers in
C (with the
prefix 0b):
- A number that starts with the prefix 0b (ZERO b) is considered to use the Binary Number System as representation
Example:
0bxxxxxxxx = the binary number xxxxxxxx Example: 0b00001111 = 15 decimal
- Example:
int main( int argc, char* argv[] ) { char a = 0; /* 0 = 00000000 */ /* Bit pos: 76543210 */ a = a | 0b00000100; /* Now: a = 00000100 */ printf( "a = %d\n", a ); a = a | 0b00010000; /* Now: a = 00010100 */ printf( "a = %d\n", a ); }
- Example Program:
(Demo above code)
- Prog file: click here
How to run the program:
- Right click on link and
save in a scratch directory
- To compile: gcc bit-op2a.c
- To run: ./a.out
- Disadvantage of
the Binary Number System:
- The number of digits needed will grown very fast !!!
We can use other related number system to express bit patterns in more compact form
- Octal numbers uses
base 8 is the representation
Example:
Representation Value represented --------------------------------------------------- 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 10 8 11 9 12 10 ... ... 23 2*8 + 3 = 19 - The Octal number system (8)
is related
to the Binary number system (2)
because:
8 = 23Because the FONT color="blue">Octal number system (8) is related to the Binary number system (2), converting values between these systems is easy (we have discussed this at the start of this course !!!)
- Denoting Octal numbers in
C (with the
prefix 0):
- A number that starts with the prefix 0 (ZERO) is considered to use the Octal Number System as representation
Example:
0xxxxxxxx = the Octal number xxxxxxxx Example: 011 = 9 decimal (8 + 1)
- Example:
int main( int argc, char* argv[] ) { char a = 011; /* 11 Octal = 8 + 1 = 9 decimal */ printf( "a = %d\n", a ); a = 0101; /* 101 Octal = 64 + 1 = 65 decimal */ printf( "a = %d\n", a ); }
- Example Program:
(Demo above code)
- Prog file: click here
How to run the program:
- Right click on link and
save in a scratch directory
- To compile: gcc octal1.c
- To run: ./a.out
- Hexadecimal numbers uses
base 16 is the representation
Example:
Representation Value represented --------------------------------------------------- 0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 A 10 B 11 C 12 D 13 E 14 F 15 10 16 11 17 12 18 ... ... 23 2*16 + 3 = 35
- Denoting Hexadecimal numbers in
C (with the
prefix 0x):
- A number that starts with the prefix 0x (ZERO x) is considered to use the Hexadecimal Number System as representation
Example:
0xaaaaa = the Hexadecimal number aaaaa Example: 0x1A = 26 decimal (16 + 10)
- Example:
int main( int argc, char* argv[] ) { int a = 0x1A; /* 1A Hexadecimal = 16 + 10 = 26 decimal */ printf( "a = %d\n", a ); a = 0x10A; /* 101 Hexadecimal = 256 + 10 = 266 decimal */ printf( "a = %d\n", a ); }
- Example Program:
(Demo above code)
- Prog file: click here
How to run the program:
- Right click on link and
save in a scratch directory
- To compile: gcc hexadec1.c
- To run: ./a.out