Asuka Kenji's Blog

2009-01-29

Master Boot Record

/**
 * From Solaris x86, /usr/include/dktp/fdisk.h
 */

struct fdisk_partition {
    unsigned char bootid;           /* bootable?  0=no, 128=yes  */
    unsigned char beghead;          /* beginning head number */
    unsigned char begsect;          /* beginning sector number */
    unsigned char begcyl;           /* 10 bit nmbr, with high 2 bits put in begsect */
    unsigned char systid;           /* Operating System type indicator code */
    unsigned char endhead;          /* ending head number */
    unsigned char endsect;          /* ending sector number */
    unsigned char endcyl;           /* also a 10 bit nmbr, with same high 2 bit trick */
    int relsect;                    /* first sector relative to start of disk */
    int numsect;                    /* number of sectors in partition */
};

struct master_boot_record {
    char    bootinst[446];          /* space to hold actual boot code */
    char    parts[4 * sizeof (struct fdisk_partition_table)];
    ushort  signature;              /* set to 0xAA55 to indicate PC MBR format */
};





/**
 * From util-linux-2.12r/fdisk/fdisk.h
 */

#define sector(s) ((s) & 0x3f)
#define cylinder(s, c) ((c) | (((s) & 0xc0) << 2))

struct partition {
    unsigned char boot_ind;         /* 0x80 - active */
    unsigned char head;             /* starting head */
    unsigned char sector;           /* starting sector */
    unsigned char cyl;              /* starting cylinder */
    unsigned char sys_ind;          /* What partition type */
    unsigned char end_head;         /* end head */
    unsigned char end_sector;       /* end sector */
    unsigned char end_cyl;          /* end cylinder */
    unsigned char start4[4];        /* starting sector counting from 0 */
    unsigned char size4[4];         /* nr of sectors in partition */
} PACKED;

2008-07-01

convention

LAST UPDATED: 2008-07-03

Shortcuts: C C++ Java PHP Python Ruby

Ruby:

# The name of a class name is a noun.
# Camel case is used.
# (Every word starts with an upper case letter.)
class RectangularShape
    
    # The name of a class constant if a noun.
    # The name must start with an upper case letter
    #   as required by the language.
    MAXIMUM_WIDTH = 1024
    MAXIMUM_HEIGHT = 768
    
    # The name of a class variable is a noun.
    # The name must start with "@@"
    #   as required by the language.
    # Lower case letters are used.
    # Every word is separated by an underscore.
    @@instance_count = 0
    
    # The name of a class accessor method
    #   has the same name as the class variable.
    def self.instance_count
        @@instance_count
    end
    
    # Constructors must be named "initialize"
    #   as required by the language.
    def initialize(x, y, w, h)
        @instance_id = @@instance_count++
        @x_coordinate = x
        @y_coordinate = y
        @width = w
        @height = h
    end
    
    # The name of an instance accessor method
    #   has the same name as the instance variable.
    def instance_id
        # The name of an instance variable is a noun.
        # The name must start with "@"
        #   as required by the language.
        # Lower case letters are used.
        # Every word is separated by an underscore.
        @instance_id
    end
    
    def x_coordinate
        @x_coordinate
    end
    
    def y_coordinate
        @y_coordinate
    end
    
    def width
        @width
    end
    
    def height
        @height
    end
    
    # The name of a method starts with a verb.
    # Lower case letters are used.
    # Every word is separated by an underscore.
    def move_to(x, y)
        @x_coordinate = x
        @y_coordinate = y
    end
    
    def contains?(x1, y1)
        # The name of a local variables starts
        #   with a lower case letter or an underscore.
        # Short forms or single letter names are used.
        # Every word is optionally delimited by an underscore.
        retval = (x1 >= @x_coordinate) &&
                 (x1 < @x_coordinate + @width) &&
                 (y1 >= @y_coordinate) &&
                 (y1 < @y_coordinate + @height)
    end
end

# The name of a global variable is a noun.
# Lower case letters are used.
# Every word is separated by an underscore.
$debug_mode = 0

variable

Ruby:

# All Ruby variables hold objects.
# Therefore, integers are objects.
a = 1

# Parallel assignment
b, c, d = 2, 3, 4

constant

Ruby:

# Ruby constants begin with a capital letter.

# This is a constant.
# This style is recommended.
# Upper case delimited by underscore distinguishes
#   a constants from a class.
MY_CONSTANT = 1

# This is also a constant.
# Camel case is used in this example.
MyConstant = 2

2008-06-25

if-elseif-else

LAST UPDATED: 2008-07-03

Shortcuts: C C++ Java PHP Python Ruby

C:

if (1 + 1 != 2) {
    printf("1 + 1 is not 2.\n");
} else if (1 + 1 == 2) {
    printf("1 + 1 is 2.\n");
} else {
    printf("This will NOT be printed.\n");
}

C++:

if (1 + 1 != 2) {
    cout << "1 + 1 is not 2." << endl;
} else if (1 + 1 == 2) {
    cout << "1 + 1 is 2." << endl;
} else {
    cout << "This will NOT be printed." << endl;
}

Java:

if (1 + 1 != 2) {
    System.out.println("1 + 1 is not 2.");
} else if (1 + 1 == 2) {
    System.out.println("1 + 1 is 2.");
} else {
    System.out.println("This will NOT be printed.");
}

PHP:

# if-elseif-else (normal syntax)
if (1 + 1 != 2) {
    echo '1 + 1 is not 2.', "\n";
} elseif (1 + 1 == 2) {
    echo '1 + 1 is 2.', "\n";
} else {
    echo 'This will NOT be printed.', "\n";
}

# if-elseif-else (alternate syntax)
if (1 + 1 != 2):
    echo '1 + 1 is not 2.', "\n";
elseif (1 + 1 == 2):
    echo '1 + 1 is 2.', "\n";
else:
    echo 'This will NOT be printed.', "\n";
endif;

Python:

if 1 + 1 != 2:
    print '1 + 1 is not 2.'
elif 1 + 1 == 2:
    print '1 + 1 is 2.'
else
    print 'This will NOT be printed.'

Ruby:

# if-elseif-else (normal syntax)
if 1 + 1 != 2 then
    puts '1 + 1 is not 2.'
elsif 1 + 1 == 2:
    puts '1 + 1 is 2.'
else
    puts 'This will NOT be printed.'
end

# if-elseif-else (without "then")
if 1 + 1 != 2
    puts '1 + 1 is not 2.'
elsif 1 + 1 == 2:
    puts '1 + 1 is 2.'
else
    puts 'This will NOT be printed.'
end

# if-elseif-else (prefixed syntax)
if 1 + 1 != 2: puts '1 + 1 is not 2.'
elsif 1 + 1 == 2: puts '1 + 1 is 2.'
else: puts 'This will NOT be printed.'
end

# if (prefixed syntax)
if 1 + 1 == 2: puts '1 + 1 is 2.' end

# if (suffixed syntax)
puts '1 + 1 is 2.' if 1 + 1 == 2

for-loop

LAST UPDATED: 2008-07-03

Shortcuts: C C++ Java PHP Python Ruby

C:

/* Prints 0, 1, 2, ... 9 */
int i;
for (i = 0; i < 10; ++i) {
    printf("%d\n", i);
}

C++:

// Prints 0, 1, 2, ... 9
for (int i = 0; i < 10; ++i) {
    cout << i << endl;
}

Java:

// for-loop
// Prints 0, 1, 2, ... 9
for (int i = 0; i < 10; ++i) {
    System.out.println(i);
}

// foreach-loop (since Java 5.0)
// This works for arrays and classes that implement Iterable.
String[] a = {"Alpha", "Beta", "Gamma", "Delta"};
for (String elem : a) {
    System.out.println(elem);
}

PHP:

# for-loop (normal syntax)
for ($i = 0; $i < 10; ++$i) {
    echo $i, "\n";
}

# for-loop (alternate syntax)
for ($i = 0; $i < 10; ++$i):
    echo $i, "\n";
endfor;

# foreach-loop (since PHP 4)
# In PHP 4, this only works for arrays.
# In PHP 5, this also works for iterating objects.

# foreach-loop (normal syntax)
$a = array('Alpha', 'Beta', 'Gamma', 'Delta');
foreach ($a as $elem) {
    echo $elem, "\n";
}

# foreach-loop (alternate syntax)
$a = array('Alpha', 'Beta', 'Gamma', 'Delta');
foreach ($a as $elem):
    echo $elem, "\n";
endforeach;

# foreach-loop (normal syntax)
$a = array(
    'A' => 'Alpha',
    'B' => 'Beta',
    'C' => 'Gamma',
    'D' => 'Delta'
);
foreach ($a as $key => $value) {
    echo $key, "\t", $value, "\n";
}

# foreach-loop (alternate syntax)
$a = array(
    'A' => 'Alpha',
    'B' => 'Beta',
    'C' => 'Gamma',
    'D' => 'Delta'
);
foreach ($a as $key => $value):
    echo $key, "\t", $value, "\n";
endforeach;

Python:

# for-loop (with range(), ascending)
# Prints 0, 1, 2, ... 9
for i in range(10):
    print i

# for-loop (with range(), ascending)
# Prints 0, 1, 2, ... 9
for i in range(0, 10):
    print i

# for-loop (with range(), descending)
# Prints 10, 9, 8, ... 1
for i in range(10, 0, -1):
    print i

# foreach-loop
a = ['Alpha', 'Beta', 'Gamma', 'Delta']
for elem in a:
    print elem

Ruby:

# for-loop (inclusive range)
# Prints 0, 1, 2, ... 9
for i in 0..9 do
    puts i
end

# for-loop (exclusive range)
# Prints 0, 1, 2, ... 9
for i in 0...10 do
    puts i
end

# for-loop (with upto())
# Prints 0, 1, 2, ... 9
0.upto(9) do |i|
    puts i
end

# for-loop (with downto())
# Prints 10, 9, 8, ... 1
10.upto(1) do |i|
    puts i
end

# for-loop (brace style)
# Prints 10, 9, 8, ... 1
# "{}" style to write "do ... end"
10.upto(1) { |i|
    puts i
}

Comments

LAST UPDATED: 2008-06-25

Shortcuts: C C++ Java PHP Python Ruby

C:

/*
C style
multiple line
comment
*/

C++:

// C++ style single line comment

/*
C style
multiple line
comment
*/

Java:

// C++ style single line comment

/*
C style
multiple line
comment
*/

/**
 * Javadoc comment
 */

PHP:

// C++ style single line comment

# Perl style single line comment

/*
C style
multiple line
comment
*/

Python:

# Perl style single line comment

# Below is an encoding comment:
# -*- coding: iso-8859-15 -*-

Ruby:

# Perl style single line comment

=begin
Ruby style
multiple line
comment
=end

Asuka Kenji's Blog

2009-01-29

Master Boot Record

2008-07-01

convention

variable

constant

2008-06-25

if-elseif-else

for-loop

Comments

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