Assembly Language for the x86 Processor Quiz

Answer: july_2012

The name of an identifier in assembly language can only contain letters, numbers, underscores, and these following symbols: $, @, and ?. However, it cannot start with a number, contain any additional symbols, or be a reserved​ word. It also cannot exceed 247 characters.

Answer: ECX

When using the LOOP instruction, the ECX register keeps track of how many times a loop iterates. The loop stops when ECX=0. CX is used in 16 bit mode, and CL is used in 8 bit mode.

Answer: 9.54

REAL4 is a 32 bit data type that represents fractional numbers in IEEE format. It has a maximum value of about 1.7*10^38.

Answer: When an assembly language instruction yields an even number of 1 bits

Adding 1 to the binary number 10010010b will set the parity flag to 1 since its sum 10010011b will yield four 1 bits.

Answer: anArray+6

The identifier anArray by itself points to the first element in the array (in this case, anArray points to 19). Subsequent elements in an array are accessed by incrementing the offset of the array by the number of bytes in it. Since anArray is assumed to be 16 bits or 2 bytes, the offset is incremented by 2. 4C0h is the element written in base 16 and it is the last element in the array, so the expression that accesses it is (((anArray+2)+2)+2)=anArray+6.

Answer: ja

The code snippet in this question​ compares the value in the al register to a particular value. It then makes jumps based on whether the value in the al register is greater than, less than or equal to the value being tested. If the value in the al is greater than the number tested, ja (jump if above) will execute whereas if the value in the al register is less than the value tested, jb (jump if below) will execute.

However, if the value in the al register is the same as the value tested, je (jump if equal) will execute.

It also test to see if al=0 in which the jz (jump if 0) will executed​. Since 232 is greater than 135, the ja instruction will execute.

Answer: 00, 84, D7, 17

In little endian mode, memory holds data from the least significant byte to the most significant byte. In this case, byte 00h is stored at offset 0000, byte 84h at offset 0001, byte D7h at offset 0002, and byte 17h at offset 0003.

Answer: 10110011b

1 XOR 1 is 0, 1 XOR 0 is 1, 0 XOR 1 is 1, and 0 XOR 0 is 0.

Answer: TYPE

The way the TYPE operator counts the bytes in an identifier is as follows:

BYTE/SBYTE-1 byte
WORD/SWORD-2 bytes
DWORD/SDWORD-4 bytes
FWORD-6 bytes
QWORD-8 bytes
TBYTE-10 bytes
REAL4-4 bytes
REAL8-8 bytes
REAL10-10 bytes

Answer: '?', -99, 'j', 0, 59, 'M'

The last item pushed into the stack will be the first item that is popped. Then the second to last item pushed into the stack will be the second item that is popped and so on.