Bitwise Operators and Enumeration Types

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Bitwise Operators and Enumeration Types
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Outline

• Bitwise Operators and Expressions
• Masks
• Software Tools Printing an int Bitwise
• Packing and unpacking
• Enumeration Types
• Example

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Bitwise Operators and Expressions

• Bitwise Operators act on integral expressions
  represented as strings of binary digits
• These operators are system dependent. Here we
  restrict our discussion to machines having 8-bit
  bytes, 4-byte words

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Bitwise Operators and Expressions

• Bitwise Operators

logical operators (unary) bitwise
complement (binary) bitwise and
(binary) bitwise exclusive or (binary)
bitwise include or shift operators (binary)
left shift ltlt (binary) right shift gtgt
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Bitwise Operators and Expressions

• Bitwise 's rule of precedence

() (postfix) -- (postfix) left to
right (prefix) --(prefix) !
sizeof(type) (unary) - (unary) (address)
(derefence) right to left /
left to right - left to right ltlt
gtgt left to right lt lt gt gt left to
right
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Bitwise Operators and Expressions

• Bitwise 's rule of precedence

! left to right left to
right left to right left to
right left to right left to
right ? right to left - /
gtgt ltlt right to
left , left to right
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Bitwise Operators and Expressions

• Operator one's complement operator, or bitwise
  complement operator

int a70707 The binary representation of a
is 00000000 00000001 00010100 00110011 The
expression a is the bitwise complement of a. it
has binary representation 11111111 11111110
11101011 11001100
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Bitwise Operators and Expressions

• Two-complement

• int n binary representation bitwise
  complement two-complement
• 00000000 00000111 11111111 11111000 11111111
  11111001
• 00000000 00001000 11111111 11110111 11111111
  11111000
• 00000000 00001001 11111111 11110110 11111111
  11110111
• -7 11111111 11111001 00000000 00000110 00000000
  00000111

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Bitwise Operators and Expressions

• Bitwise Binary Logical Operators

• a b ab ab ab
• 0 0 0 0 0
• 0 0 1 1
• 0 1 0 1 1
• 1 1 1 0 1

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Bitwise Operators and Expressions

• Example

int a33333, b77777 expr presentation value
a 00000000 00000000 100000010
00110101 33333 b 11111111 11111110 110100000
00101111 -77777 ab 00000000 00000000 100000000
00100101 32805 ab 11111111 11111110 01010010
00011010 -110054 ab 11111111 11111110
11010010 00111111 -77249 (ab) 00000000
00000001 00101101 11000000 77248 (ab) 0000000
0 00000001 00101101 11000000 77248
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Bitwise Operators and Expressions

• Left and right shift operators

expr1ltltexpr2 char c'Z' expression
representation action c 00000000 00000000
00000000 01011010 un-shifted cltlt1 00000000
00000000 00000000 10110100 left-shifted
1 cltlt4 00000000 00000000 00000101 10100000
left-shifted 4 cltlt31 00000000 00000000 00000000
00000000 left-shifted 31
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Bitwise Operators and Expressions

• Left and right shift operators

expr1gtgtexpr2 int a1ltlt31 unsigned
b1ltlt31 expression representation action
a 10000000 00000000 00000000
01000010 un-shifted agtgt31 11110000 00000000
00000000 00000000 right-shifted 3 b 00000000
00000000 00000000 00000000 un-shifted bgtgt3 00
010000 00000000 00000000 00000000
right-shifted 3
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Bitwise Operators and Expressions

• Mixed Left and right shift operators

unsigned a1 n2 expression equivalent
representation value altltbgtgt1 (altltb)gtgt1 000000000
00000010 2 altlt12ltlt3 (altlt(12))ltlt3 00000000
011111111 64 abltlt12agtgtb ((ab)ltlt(12a))gtgtb
00001100 00000000 3072
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Masks

• A mask is a constant or variable that is used to
  extract desired bits from another variable or
  expressions.

int i, mask1 for (i0ilt10 i) printf("d",
imask)
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Example How to print an int bitwise
/ Bit print an int expression. / include
ltlimits.hgt void bit_print(int a) int i
int n sizeof(int) CHAR_BIT / in
limits.h / int mask 1 ltlt (n - 1)
/ mask 100...0 /
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Example How to print an int bitwise
for (i 1 i lt n i) putchar(((a
mask) 0) ? '0' '1') a ltlt 1 if
(i CHAR_BIT 0 i lt n) putchar('
')
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Example How to print an int bitwise
Input an integer 2 2 00000000 00000000
00000000 00000010 Input an integer 3 3
00000000 00000000 00000000 00000011 Input an
integer 5 5 00000000 00000000 00000000
00000101 Input an integer 43 43 00000000
00000000 00000000 00101011
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include ltstdio.hgt void bit_print(int a) int
main(void) int k for ( )
printf("Input an integer ") if
(scanf("d", k) ! 1) break
printf("\n7d ", k) bit_print(k)
printf("\n\n") printf("\nBye!\n\n")
return 0
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Packing and Unpacking

• Use bitwise expressions allow for data
  compression across bye boundaries.
• This is very useful for saving space, but can not
  even more useful in saving time.

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/ Pack 4 characters into an int. / include
ltlimits.hgt int pack(char a, char b, char c, char
d) int p a / p will be
packed with a, b, c, d / p (p ltlt CHAR_BIT)
b p (p ltlt CHAR_BIT) c p (p ltlt
CHAR_BIT) d return p
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/ Unpack a byte from an int. / include
ltlimits.hgt char unpack(int p, int k)
/ k 0, 1, 2, or 3 / int n
k CHAR_BIT / n 0, 8, 16, or 24
/ unsigned mask 255 /
low-order byte / mask ltlt n return ((p
mask) gtgt n)
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Enumeration Type

• naming a finite set

enum day sun, mon, tue, wed, thu, fri, sat
0 1 2 3 4 5 6
declaration enum day d1, d2
That means one of the days can be assign to the
enum variable d1 or d2
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Enumeration Type

• enum's declaration and initialization

enum suit club1, diamonds, hearts, spades
a, b,c 1 2 3
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enum fruit apple7, pear, orange3, lemon
frt 7 8 3 4
enum vegbeet17, carrot17, corn17 veg1, veg2
enum fir, pine tree
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includeltstdio.hgt enum day sun, mon, tue, wed,
thu, fri, sat typedef enum day day day
find_next_day(day d) day next_day switch(d) c
ase sun next_daymon break case mon
next_daytue break
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case tue next_daywed break case wed
next_daythu break case thu next_dayfri
break case fri next_daysat
break return next_day
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/ The game of paper, rock, scissors.
/ include ltctype.hgt / for isspace()
/ include ltstdio.hgt / for printf(), etc
/ include ltstdlib.hgt / for rand() and
srand() / include lttime.hgt / for
time() / enum p_r_s paper, rock, scissors,
game, help, instructions, quit enum
outcome win, lose, tie, error typedef enum
p_r_s p_r_s typedef enum outcome
outcome
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outcome compare(p_r_s player_choice,
p_r_s machine_choice) void
wrt_final_status(int win_cnt, int lose_cnt) void
wrt_game_status(int win_cnt, int lose_cnt,
int tie_cnt) void wrt_help(void) void
wrt_instructions(void) void
report_and_tabulate(outcome result,
int win_cnt_ptr, int lose_cnt_ptr, int
tie_cnt_ptr) p_r_s selection_by_machine(void
) p_r_s selection_by_player(void)
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include "p_r_s.h" outcome compare(p_r_s
player_choice, p_r_s machine_choice) outcome
result if (player_choice
machine_choice) return tie switch
(player_choice) case paper result
(machine_choice rock) ? win lose
break case rock result
(machine_choice scissors) ? win lose
break
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case scissors result (machine_choice
paper) ? win lose break default
printf("\nPROGRAMMER ERROR Unexpected
choice!\n\n") exit(1) return
result
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include "p_r_s.h" void report_and_tabulate(outco
me result, int win_cnt_ptr, int
lose_cnt_ptr, int tie_cnt_ptr) switch
(result) case win win_cnt_ptr
printf("27sYou win.\n", "") break
case lose lose_cnt_ptr
printf("27sYou lose.\n", "") break
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case tie tie_cnt_ptr
printf("27sA tie.\n", "") break
default printf("\nPROGRAMMER ERROR
Unexpected result!\n\n") exit(1)
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include "p_r_s.h" p_r_s selection_by_machine(voi
d) return ((p_r_s) (rand() 3)) p_r_s
selection_by_player(void) char c
p_r_s player_choice printf("Input p, r, or
s ") while (isspace(c getchar())) /
skip white space / switch (c)
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case 'p' player_choice paper
break case 'r' player_choice rock
break case 's' player_choice
scissors break case 'g'
player_choice game break case 'i'
player_choice instructions break
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case 'q' player_choice quit
break default player_choice help
break return player_choice
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include "p_r_s.h" void wrt_final_status(int
win_cnt, int lose_cnt) if (win_cnt gt
lose_cnt) printf("CONGRATULATIONS - You
won!\n\n") else if (win_cnt lose_cnt)
printf("A DRAW - You tied!\n\n") else
printf("SORRY - You lost!\n\n")
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void wrt_game_status(int win_cnt, int lose_cnt,
int tie_cnt) printf("\ns\ns4d\ns4d\ns4
d\ns4d\n\n", "GAME STATUS", "
Win ", win_cnt, " Lose ", lose_cnt,
" Tie ", tie_cnt, " Total ",
win_cnt lose_cnt tie_cnt) void
wrt_help(void) printf("\ns\n", "The
following characters can be used for input\n"
" p for paper\n" " r for
rock\n"
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" s for scissors\n" " g print
the game status\n" " h help, print
this list\n" " i reprint the
instructions\n" " q quit this
game\n") void wrt_instructions(void)
printf("\ns\n", "PAPER, ROCK,
SCISSORS\n" " In this game p is for
\"paper,\" r is for \"rock,\" and" " s is
for \"scissors.\"\n" " Both the player
and the machine\n" " will choose one of
p, r, or s." " If the two choices are the
same,\n"
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" then the game is a tie. Otherwise\n"
" \"paper covers the rock\" (a win for
paper),\n" " \"rock breaks the
scissors\" (a win for rock),\n" "
\"scissors cut the paper\" (a win for
scissors).\n" "\n" " There are
other allowable inputs\n" " g for
game status (the number of wins so far),\n"
" h for help,\n" " i for
instructions (reprint these instructions),\n"
" q for quit (to quit the
game).\n" "\n" " This game is
played repeatedly until q is entered.\n"
"\n" " Good luck!\n")
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Example Game of Paper, Rock, Scissors
PAPER, ROCK, SCISSORS In this game p is for
"paper," r is for "rock," and s is for
"scissors." Both the player and the machine
will choose one of p, r, or s. If the two
choices are the same, then the game is a tie.
Otherwise "paper covers the rock" (a
win for paper), "rock breaks the scissors"
(a win for rock), "scissors cut the paper"
(a win for scissors).
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There are other allowable inputs g for
game status (the number of wins so far),
h for help, i for instructions
(reprint these instructions), q for quit
(to quit the game). This game is
played repeatedly until q is entered. Good
luck!
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Input p, r, or s p A
tie. Input p, r, or s s
You win. Input p, r, or s s
You win. Input p, r, or s s
You lose. Input p, r, or s s
A tie. Input p, r, or s
s You lose.