Using C, complete the implementation of the set_bit, flip_bits, clear_bit, and t

ID: 3718602 • Letter: U

Question

Using C, complete the implementation of the set_bit, flip_bits, clear_bit, and toggle_bit functions. To complete the program, follow the instructions detailed in the in-line comments in the skeleton code below.

SAMPLE RESULTS:

$ ./sample_test_driver
set_bit(01100001, 7) = 11100001
flip_bits(01100001 ) = 10011110
clear_bit(01100001, 7) = 01100001
toggle_bit(01100001, 7) = 11100001

set_bit(00111101, 2) = 00111101
flip_bits(00111101 ) = 11000010
clear_bit(00111101, 2) = 00111001
toggle_bit(00111101, 2) = 00111001

set_bit(00100101, 3) = 00101101
flip_bits(00100101 ) = 11011010
clear_bit(00100101, 3) = 00100101
toggle_bit(00100101, 3) = 00101101

set_bit(10000101, 4) = 10010101
flip_bits(10000101 ) = 01111010
clear_bit(10000101, 4) = 10000101
toggle_bit(10000101, 4) = 10010101

set_bit(00010001, 1) = 00010011
flip_bits(00010001 ) = 11101110
clear_bit(00010001, 1) = 00010001
toggle_bit(00010001, 1) = 00010011

Code:

#include <stdio.h>
#include <stdlib.h>

// Copy macros.h into your work directory if you want to use these macros.
#include "macros.h"

typedef unsigned char byte;

byte set_bit(byte register_value, int pin) {
// (a) Modify the register value by setting the designated pin
// to 1 without altering the other pins, and return the result.
// Hint: left shift; binary OR.
}

byte flip_bits(byte register_value) {
// (b) Flip all bits in the register value so that each bit that
// is originally 1 becomes 0, and each bit that is originally 0
// becomes 1.
// Hint: binary NOT.
}

byte clear_bit(byte register_value, int pin) {
// (c) Modify the register value by clearing the designated pin
// (that is, setting it to 0) without altering any other pins, and
// return the result.
// Hint: left shift; binary NOT; binary AND.
}

byte toggle_bit(byte register_value, int pin) {
// (d) Modify the supplied register value by flipping the designated
// pin, leaving all other pins unchanged.
// Hint: left shift; binary XOR.
}

//-----------------------------------------------------------
#define REPEATS (5)
#define BYTE_COUNT (256)
#define PIN_COUNT (8)
#define SEED ((unsigned) 314159)
//-----------------------------------------------------------

/*
** Convert a byte to an integer with digits that look like the binary
** representation of the byte.
**
** For example:
** binstr(0x0c) == 1100, and
** binstr(0xcc) == 11001100.
*/
int binstr(byte b) {
int result = 0;

for ( int i = 7; i >= 0; i-- ) {
result = result * 10 + ((b >> i) & 1);
}

return result;
}
//-----------------------------------------------------------
int main(void) {
srand(SEED);

for ( int i = 0; i < REPEATS; i++ ) {
byte register_value = rand() % BYTE_COUNT;
int pin = rand() % PIN_COUNT;

if ( i > 0 ) printf(" ");

printf(" set_bit(%08d, %d) = %08d ", binstr(register_value), pin, binstr( set_bit(register_value, pin)));
printf(" flip_bits(%08d ) = %08d " , binstr(register_value), binstr( flip_bits(register_value )));
printf(" clear_bit(%08d, %d) = %08d ", binstr(register_value), pin, binstr( clear_bit(register_value, pin)));
printf("toggle_bit(%08d, %d) = %08d ", binstr(register_value), pin, binstr(toggle_bit(register_value, pin)));
}
return 0;
}

Explanation / Answer

#include <stdio.h>
#include <stdlib.h>

typedef unsigned char byte;

byte set_bit(byte register_value, int pin) {
    // (a) Modify the register value by setting the designated pin
    // to 1 without altering the other pins, and return the result.
    // Hint: left shift; binary OR.
   register_value |= (1<<pin);
   return register_value;
}

byte flip_bits(byte register_value) {
    // (b) Flip all bits in the register value so that each bit that
    // is originally 1 becomes 0, and each bit that is originally 0
    // becomes 1.
    // Hint: binary NOT.
   register_value = ~register_value;
   return register_value;
}

byte clear_bit(byte register_value, int pin) {
    // (c) Modify the register value by clearing the designated pin
    // (that is, setting it to 0) without altering any other pins, and
    // return the result.
    // Hint: left shift; binary NOT; binary AND.
   register_value &= ~(1 << pin);
   return register_value;
}

byte toggle_bit(byte register_value, int pin) {
    // (d) Modify the supplied register value by flipping the designated
    // pin, leaving all other pins unchanged.
    // Hint: left shift; binary XOR.
   register_value ^= 1<<pin;
   return register_value;

}

int binstr(byte b) {
int result = 0;

    for ( int i = 7; i >= 0; i-- ) {
        result = result * 10 + ((b >> i) & 1);
    }

return result;
}
//-----------------------------------------------------------
int main(void) {
srand(SEED);

    for ( int i = 0; i < REPEATS; i++ ) {
        byte register_value = rand() % BYTE_COUNT;
        int pin = rand() % PIN_COUNT;

if ( i > 0 ) printf(" ");

        printf("   set_bit(%08d, %d) = %08d ", binstr(register_value), pin, binstr(   set_bit(register_value, pin)));
        printf(" flip_bits(%08d   ) = %08d " , binstr(register_value),      binstr( flip_bits(register_value     )));
        printf(" clear_bit(%08d, %d) = %08d ", binstr(register_value), pin, binstr( clear_bit(register_value, pin)));
        printf("toggle_bit(%08d, %d) = %08d ", binstr(register_value), pin, binstr(toggle_bit(register_value, pin)));
    }
    return 0;
}

void process_game_controller( void ) {
    // (f) Test the relevant pin in the Port D input register to determine
    // if the Up switch is closed. If it is, turn on both LEDs without
    // disrupting any other pins.
   if ((PIND >> 1) & 0b1) {
       PORTB = PORTB | 0b00001100;
       } else {
    // (g) OTHERWISE, test the relevant pin of the Port B input register
    // to determine if the Down switch is closed. If it is, turn off both LEDs
    // without affecting any other pins.
   if ((PINB >> 7) & 0b1) {
       PORTB = PORTB & 0b11110011;
       } else {
    // (h) OTHERWISE, test the relevant pin of the Port B input register
    // to determine if the Left switch is closed. If it is, turn on the left LED
    // and turn off the right LED without affecting any other pins.
   if ((PINB >> 1) & 0b1) {
       PORTB = PORTB | 0b00000100;
       PORTB = PORTB & 0b00001000;
       } else {
   // (i) OTHERWISE, test the relevant pin of the Port D input register
    // to determine if the Right switch is closed. If it is, turn on the right LED
    // and turn off the left LED without affecting any other pins.
   if ((PIND >> 0) & 0b1) {
       PORTB = PORTB | 0b00001000;
       PORTB = PORTB & 0b00000100;
       } else {
    if ((PINB >> 0) & 0b1) {
       PORTB = PORTB | 0b00001100;
   }
       }
       }
       }
       }
}

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