Strings

Question 1

Strings may have an actual value _______ than the total numbers of cells declared.

Answer 1

less

Question 2

Strings operands use ___ and ___ registers.

Answer 2

RSI and RDI

Question 3

As part of execution, string instructions automatically __________________________ the index registers used by them.

Answer 3

update (increment or decrement)

Question 4

The direction of string processing (forward or backward) is controlled by the ____________.

Answer 4

Direction flag

Question 5

If the direction flag is clear (DF = 0). string operations proceed in ________ direction.

Answer 5

forward (from head to tail)

Question 6

Two instructions to explicitly manipulate the direction flag:

Answer 6

std: set direction flag (DF = 1)
cld: clear direction flag (DF = 0)

Question 7

String instructions can accept a ________ ________ to repeatedly execute the operation.

Answer 7

repetition prefix

Question 8

Unconditional repeat prefix which causes the instruction to repeat according to the value in the RCX register.

Answer 8

rep

Question 9

Operations similar to that of rep except that repetition is also conditional on the zero flag. Stops the repetition when ZF is 0.

Answer 9

repe / repz

Question 10

Operations similar to that of rep except that repetition is also conditional on the zero flag. Stops the repetition when ZF is 1.

Answer 10

repne / repnz

Question 11

Copies the value from the source string to the A register

Answer 11

Load a String (LODS)

Question 12

Copies the value from the A register to the destination string (RDI)

Answer 12

Store a string (STOS)

Question 13

Compares the two bytes, words, doublewords, or quadwords at RSI and RDI and sets the flags.

Answer 13

Compare strings (CMPS)

Question 14

CMPS performs: ___ - ___ and sets the flags according to the result.

Answer 14

RSI - RDI

Question 15

Useful in searching for a particular value or character in a string.

Answer 15

Scanning a String (SCAS)