What is x86 assembly used for?
x86 assembly language is the name for the family of assembly languages which provide some level of backward compatibility with CPUs back to the Intel 8008 microprocessor, which was launched in April 1972. It is used to produce object code for the x86 class of processors.
What is Movzbl Assembly?
● so movzbl means: move a byte with zero extension into 32-bit (“l”) register; last byte of. register is that byte, all others are zero. ● (zero extension means to put zeroes into the remaining unused bytes of the register)
What is Cmpl Assembly?
Purpose. Compares the contents of two general-purpose registers logically. Syntax. Bits.
What is the AL register?
The least significant byte of AX can be used as a single 8-bit register called AL, while the most significant byte of AX can be used as a single 8-bit register called AH. These names refer to the same physical register. When a two-byte quantity is placed into DX, the update affects the value of DH, DL, and EDX.
WHAT IS EBX register?
EBX,BX,BH,BL : Called the Base register It is used as a base pointer for memory access Gets some interrupt return values ECX,CX,CH,CL : Called the Counter register It is used as a loop counter and for shifts Gets some interrupt values EDX,DX,DH,DL : Called the Data register It is used for I/O port access, arithmetic.
What is Lea assembly?
The lea instruction places the address specified by its first operand into the register specified by its second operand. Note, the contents of the memory location are not loaded, only the effective address is computed and placed into the register.
What is Lea Assembly?
lea — Load effective address. The lea instruction places the address specified by its first operand into the register specified by its second operand. Note, the contents of the memory location are not loaded, only the effective address is computed and placed into the register.
What does Movslq mean in assembly?
MOVSLQ is move and sign-extend a value from a 32-bit source to a 64-bit destination. MOVSLQ is move and sign-extend a value from a 32-bit source to a 64-bit destination.
What does 0x8 (% RSP mean?
0x8(%rsp) means “get the location on the stack that is 8 bytes away from the stack pointer %rsp, and then take the value at that address.” It moves 0x131 into %eax, and then compares it to the data at that location.
What is RDX register used for?
Registers
| Register | Purpose | Saved across calls |
|---|---|---|
| %rdx | used to pass 3rd argument to functions | No |
| %rsp | stack pointer | Yes |
| %rbp | callee-saved; base pointer | Yes |
| %rsi | used to pass 2nd argument to functions | No |
What is the difference between EAX and AX?
eax is the 32-bit, “int” size register. It was added in 1985 during the transition to 32-bit processors with the 80386 CPU. I’m in the habit of using this register size, since they also work in 32 bit mode, although I’m trying to use the longer rax registers for everything. ax is the 16-bit, “short” size register.
What is a register x86?
General Purpose Registers (GPRs) The x86 architecture contains eight 32-bit General Purpose Registers (GPRs). These registers are mainly used to perform address calculations, arithmetic and logical calculations. Four of the GPRs can be treated as a 32-bit quantity, a 16-bit quantity or as two 8-bit quantities.
What is assembler?
Assembler is a program for converting instructions written in low-level assembly code into relocatable machine code and generating along information for the loader. Attention reader! Don’t stop learning now.
Should I read this chapter before using flat assembler?
If you are experienced assembly language programmer, you should read at least this chapter before using this compiler. Flat assembler is a fast assembly language compiler for the x86 architecture processors, which does multiple passes to optimize the size of generated machine code.
Does the assembler enforce the idea of a constant?
The assembler enforces very little, and certainly not the idea of a constant. Nevertheless, the idea of using a DISdirective might be too strange for some students. More On DC (Define Constant)
What is the difference between FSTSW and fnstsw?
fstsw and fnstsw store the current value of the FPU status word in the destination location. The destination operand can be either a 16-bit memory or the AX register. fstsw checks for pending unmasked FPU exceptions before storing the status word, fnstsw does not.