meaning of bit bang

1. bit bang Transmission of data on a serial line accomplished by rapidly changing a single output bit, in software, at the appropriate times. The technique is a simple loop with eight OUT and SHIFT instruction pairs for each byte. Input is more interesting. And full-duplex doing input and output at the same time is one way to separate the real hackers from the wannabees. Bit bang was used on certain early models of Prime computers, presumably when UARTs were too expensive, and on archaic Zilog Z80 micros with a Zilog PIO but no SIO. In an interesting instance of the cycle of reincarnation, this technique is now 1991 coming back into use on some RISC architectures because it consumes such an infinitesimal part of the processor that it actually makes sense not to have a UART. [Jargon File] bit bashing Also "bit diddling" or bit twiddling. Any of several kinds of low-level programming characterised by manipulation of bit, flag, nibble, and other smaller-than-character-sized pieces of data. These include low-level device control, encryption algorithms, checksum and error-correcting codes, hash functions, some flavours of graphics programming see bitblt, and assembler/compiler code generation. May connote either tedium or a real technical challenge more usually the former. "The command decoding for the new tape driver looks pretty solid but the bit-bashing for the control registers still has bugs. " See also bit bang, mode bit. bitblt /bitblit/ [BLT] 1. Any of a family of closely related algorithms for moving and copying rectangles of bits between main and display memory on a bit-mapped device, or between two areas of either main or display memory the requirement to do the Right Thing in the case of overlapping source and destination rectangles is what makes BitBlt tricky. 2. blit, BLT. [Jargon File] bit bucket 1. Or "write-only memory", "WOM" The universal data sink originally, the mythical receptacle used to catch bits when they fall off the end of a register during a shift instruction. Discarded, lost, or destroyed data is said to have "gone to the bit bucket". On Unix, often used for /dev/null. Sometimes amplified as "the Great Bit Bucket in the Sky". 2. The place where all lost mail and news messages eventually go. The selection is performed according to Finagles Law; important mail is much more likely to end up in the bit bucket than junk mail, which has an almost 100% probability of getting delivered. Routing to the bit bucket is automatically performed by mail-transfer agents, news systems, and the lower layers of the network. 3. The ideal location for all unwanted mail responses: "Flames about this article to the bit bucket. " Such a request is guaranteed to overflow ones mailbox with flames. 4. Excuse for all mail that has not been sent. "I mailed you those figures last week; they must have landed in the bit bucket. " Compare black hole. This term is used purely in jest. It is based on the fanciful notion that bits are objects that are not destroyed but only misplaced. This appears to have been a mutation of an earlier term "bit box", about which the same legend was current; old-time hackers also report that trainees used to be told that when the CPU stored bits into memory it was actually pulling them "out of the bit box". Another variant of this legend has it that, as a consequence of the "parity preservation law", the number of 1 bits that go to the bit bucket must equal the number of 0 bits. Any imbalance results in bits filling up the bit bucket. A qualified computer technician can empty a full bit bucket as part of scheduled maintenance. In contrast, a "chad box" is a real container used to catch chad. This may be related to the origin of the term "bit bucket" [Comments ?].

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