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Quiz based on Digital Principles and Computer Organization

1) Base of hexadecimal number system? Answer : 16 2) Universal gate in digital logic? Answer : NAND 3) Memory type that is non-volatile? Answer : ROM 4) Basic building block of digital circuits? Answer : Gate 5) Device used for data storage in sequential circuits? Answer : Flip-flop 6) Architecture with shared memory for instructions and data? Answer : von Neumann 7) The smallest unit of data in computing? Answer : Bit 8) Unit that performs arithmetic operations in a CPU? Answer : ALU 9) Memory faster than main memory but smaller in size? Answer : Cache 10) System cycle that includes fetch, decode, and execute? Answer : Instruction 11) Type of circuit where output depends on present input only? Answer : Combinational 12) The binary equivalent of decimal 10? Answer : 1010 13) Memory used for high-speed temporary storage in a CPU? Answer : Register 14) Method of representing negative numbers in binary? Answer : Two's complement 15) Gate that inverts its input signal? Answer : NOT 16)...

Transforming I/O Request to Hardware

Transforming I/O Requests to Hardware Operations
* Users appeal data using file names, which must ultimately be mapped to specific blocks of data from a specific device managed by a specific device driver.
*  DOS uses the colon separator to specify a particular device ( e.g. C:, LPT:, etc. )
* UNIX uses a mount table to map filename append ( e.g. /usr ) to specific mounted devices. Where many entries in the mount table match different appends of the filename the one that matches the longest append is chosen. ( e.g. /usr/home instead of /usr where both subsits in the mount table and both match the required file. )
* UNIX uses special device files, usually located in /dev, to represent and process physical devices directly.
• Each device file has a major and minor number related with it, stored and 
displayed where the file size could normally go.
• The high number is an index into a table of device drivers, and implies which 
device driver handles this device. ( E.g. the disk drive handler. )
• The minor number is a parameter moved to the device driver, and implies which 
particular device is to be processed, out of the many which may be handled by a 
particular device driver. ( e.g. a specific disk drive or partition. )
* A series of lookup tables and mappings makes the access of different devices adaptable, and somewhat transparent to users.
* Figure explains the steps taken to process a ( blocking ) read request:


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