Question

1. True/ False 1.1. AL refers to the left most Byte in register EAX 1.2. The easiest way to convert from a number in base 4 to a number in hexadecimal is through direct conversion. 1.3. Unsigned means by default positive 1.4. ASCII code uses 7 bits for each character. 1.5. The MSb (most significant bit) in the hexadecimal codes of the characters in the ASCII code is always 1. 1.6. The sections (segments) of a program in an assembly language (NASM, MASM etc) have to be placed in a strict order. 1.7. "resb" directive in NASM reserves 1 byte for the given variable 1.8. "int Ox80" refers to the integer with the value 80 in hexadecimal 1.9. In NASM integer constants can be represented in binary, by adding a "b" at the end of the number 1.10. A value of 4 loaded in register eax means that a system write is to be performed.

Answer 1

1.1 True.  EAX is 32 bit value where AX is the lower 16 bits (0-15). In AX, lower 8 bits (0 to 7) are AL and higher 8 bits (8-15) are AH.

1.2 True. Direct conversion is easy as for each pair of numbers x₂x₁ we can calculate decimal number as 4*x₂ + x₁ and then mapped to hexadecimal number.  

(232132)₄ = (B9E)₁₆

• 23 = 2*4 + 3 = 11 = B₁₆
• 21 = 2*4 + 1 = 9₁₆
• 32 = 3*4 + 2 = 14 = E₁₆

1.3 True. Unsigned numbers are always positive.

1.4 True. ASCII code uses 7 bit for each character. There are total 128 characters in ASCII.

1.5 False. Most significant bit in hexadecimal of ascii characters can be from 0 to 7.

1.6 False. Segments can be in any order as they are identified by their levels.

1.7 True. resb reserves 1 byte. resw reserves 2 bytes. resd reserves 4 bytes. resq reserves 8 bytes.

1.8 False. int is for interrupt here. 0x80 is the interrupt number.

1.9 True. Number can be represented as binary by putting b at the end.

1.10 True. EAX = 4 is considered as system write and 3 as read.