Questions and Answers on Direct Memory Access

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A microporgram is sequencer perform the operation   A.| Read|  B.| write|
 C. | Execute|
 D. | Read and execute|
   Answer  D
_____________________________________________________________________________________| The control unit of computer   A.| Performs ALU operations on the data|  B.| Controls the operation of the output devices|

 C. | Is a device for manually operating the computer|
 D. | Direct the other unit of computers|
   Answer  D
_____________________________________________________________________________________| Which of the following is a set of general purpose internal registers?   A.| Stack|  B.| Scratch pad|
 C. | Address register|
 D. | Status register|
   Answer  B
_____________________________________________________________________________________| P : “Program is a step by step execution of the instructions”. Given P, which of the following is true ?  A.| Program is a subset of an instruction set.|  B.| Program is a sequence of a subset of an instruction set.|  C. | Program is a partially ordered set of an instruction set.|  D. | All of the above|

   Answer  B
_____________________________________________________________________________________| Interrupts which are initiated by an I/O drive are   A.| Internal|  B.| External|
 C. | Software|
 D. | All of above|
   Answer  B
_____________________________________________________________________________________| What is meant by a dedicated computer?   A.| Which is used by one person only|  B.| Which is assigned to one and only one task|

 C. | Which does one kind of software|
 D. | Which is meant for application software only|
   Answer  B
_____________________________________________________________________________________| In which addressing mode the operand is given explicitly in the instruction   A.| Absolute|  B.| Immediate|

 C. | Indirect|
 D. | Direct|
   Answer  B
_____________________________________________________________________________________| The program counter   A.| Is a register|
 B.| During execution of the current instruction its content changes|  C. | Both A and B|
 D. | None of these|
   Answer  C
_____________________________________________________________________________________| Fetch_And_Add(X,i) is an atomic Read-Modify-Write instruction that reads the value of memory location X, increments it by the value i, and returns the old value of X. It is used in the pseudocode shown below to implement a busy-wait lock. L is an unsigned integer shared variable initialized to 0. The value of 0 corresponds to lock being available, while any non-zero value corresponds to the lock being not available. AcquireLock(L){

while (Fetch_And_Add(L,1))
L = 1;
L = 0;
This implementation  A.| fails as L can overflow|
 B.| fails as L can take on a non-zero value when the lock is actually available|  C. | works correctly but may starve some processes|
 D. | works correctly without starvation|
   Answer  B
_____________________________________________________________________________________| A complete microcomputer system consists of  A.| Microprocessor|  B.| Memory|
 C. | Peripheral equipment|
 D. | All of the above|
   Answer  D
_____________________________________________________________________________________| The addressing mode used in the instruction PUSH B is   A.| Direct|  B.| Register|
 C. | Register indirect|
 D. | Immediate|
   Answer  C
_____________________________________________________________________________________| The register used as a working area in CPU is   A.| Program counter|  B.| Instruction register|
 C. | Instruction decoder|
 D. | Accumulator|
   Answer  D
_____________________________________________________________________________________| In which addressing mode the operand is given...
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