⊿ Point. {R} Glossary. ◢ Keyword: B. ◥ University. {q} PhD. {tr} Training. ⚫ UK. ↂ EndNote. ✊ Harvey (2009) Binary system. Two astronomical bodies which orbit each other A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common kinds of binary system are binary stars and binary asteroids, but brown dwarfs, planets, neutron stars, black holes and galaxies can also form binaries.
A multiple system is similar but consists of three or more objects, for example trinary stars and trinary asteroids. Classification[edit] Binary stars are also classified based on orbit. Eclipsing binaries are where the objects' orbits are at an angle that when one passes in front of the other it causes an eclipse, as seen from Earth. Astrometric binaries are objects that seem to move around nothing as their companion object cannot be identified, it can only be inferred. Binary companion (minor planets)[edit] See also[edit] Astronomy portal References[edit] Binary-coded decimal. System of digitally encoding numbers In byte-oriented systems (i.e. most modern computers), the term unpacked BCD[1] usually implies a full byte for each digit (often including a sign), whereas packed BCD typically encodes two digits within a single byte by taking advantage of the fact that four bits are enough to represent the range 0 to 9.
The precise four-bit encoding, however, may vary for technical reasons (e.g. Excess-3). BCD's main virtue, in comparison to binary positional systems, is its more accurate representation and rounding of decimal quantities, as well as its ease of conversion into conventional human-readable representations. Its principal drawbacks are a slight increase in the complexity of the circuits needed to implement basic arithmetic as well as slightly less dense storage.
BCD per se is not as widely used as in the past, and is unavailable or limited in newer instruction sets (e.g., ARM; x86 in long mode). Decimal: 9 1 Binary : 0000 1001 0000 0001 [edit] Bit numbering. Convention to identify bit positions In computing, bit numbering is the convention used to identify the bit positions in a binary number. Bit significance and indexing [edit] Bit indexing correlates to the positional notation of the value in base 2. For this reason, bit index is not affected by how the value is stored on the device, such as the value's byte order. Least significant bit in digital steganography In digital steganography, sensitive messages may be concealed by manipulating and storing information in the least significant bits of an image or a sound file.
A diagram showing how manipulating the least significant bits of a color can have a very subtle and generally unnoticeable effect on the color. Unsigned integer example This table illustrates an example of decimal value of 149 and the location of LSb. Signed integer example This table illustrates an example of an 8 bit signed decimal value using the two's complement method. Most- vs least-significant bit first LSb 0 bit numbering. Endianness. Order of bytes in a computer word Computers store information in various-sized groups of binary bits. Each group is assigned a number, called its address, that the computer uses to access that data. On most modern computers, the smallest data group with an address is eight bits long and is called a byte.
Larger groups comprise two or more bytes, for example, a 32-bit word contains four bytes. A big-endian system stores the most significant byte of a word at the smallest memory address and the least significant byte at the largest. Big-endianness is the dominant ordering in networking protocols, such as in the Internet protocol suite, where it is referred to as network order, transmitting the most significant byte first. Computer memory consists of a sequence of storage cells (smallest addressable units); in machines that support byte addressing, those units are called bytes. Another important attribute of a byte being part of a "field" is its "significance". [edit] Variable-length data. Serial presence detect. Standardized way to automatically access information about a memory module In computing, serial presence detect (SPD) is a standardized way to automatically access information about a memory module.
Earlier 72-pin SIMMs included five pins that provided five bits of parallel presence detect (PPD) data, but the 168-pin DIMM standard changed to a serial presence detect to encode more information.[1] When an ordinary modern computer is turned on, it starts by doing a power-on self-test (POST). Since about the mid-1990s, this process includes automatically configuring the hardware currently present. Some computers adapt to hardware changes completely automatically. For a memory module to support SPD, the JEDEC standards require that certain parameters be in the lower 128 bytes of an EEPROM located on the memory module.
The SPD EEPROM firmware is accessed using SMBus, a variant of the I2C protocol. Before SPD, memory chips were spotted with parallel presence detect (PPD). [edit]