Thank you very much for the replies all. I tested them all out and am still confused about certain things, so I will definitely be doing some major reading/testing this week. I've posted this here just for completeness.

What I did find out is that I can unset all bits at a certain location by doing a negate AND using the total value of the bits I want to unset. For example, if I want to unset bits 4-3:

my $x = 0xFF;

# 0x18 == 24, the max value of both bits
# 4-3 set

printf("%b\n", &= ~0x18);

__END__

11100111

[download]

Then, I can re-set those bits by ORing the bit string with any value within the value range of those two bytes:

$x |= 0x14; # 20;

__END__

11110111

[download]

Here's my first working sample of real-world code that I've put together. I'm certain it isn't the most concise, efficient or elegant code, but it'll get better as I learn about how all the bitwise operators work. In my case, I'm dealing with a 16-bit wide configuration register that are stored as two bytes, but when working on them, I merge them together so the code more closely represents what the hardware's datasheet specifies as bit locations:

sub queue {
    my ($self, $q) = @_;

    if (defined $q){
        if (! exists $queue{$q}){
            die "queue param requires a binary string.\n";
        }
        $self->{queue} = $queue{$q};
    }

    $self->{queue} = DEFAULT_QUEUE if ! defined $self->{queue};

    my $bits = $self->bits;

    # unset
    $bits &= ~MAX_QUEUE;

    # set
    $bits |= $self->{queue};

    my $lsb = $bits & 0xFF;
    my $msb = $bits >> 8;

    $self->register($msb, $lsb);

    return $self->{queue};
}

[download]

In reply to Re: Modifying multiple bits in a byte - bitwise operators by stevieb
in thread Modifying multiple bits in a byte - bitwise operators by stevieb

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