What is the purpose of ECX register?

What is the purpose of ECX register?

CX is known as the count register, as the ECX, CX registers store the loop count in iterative operations. DX is known as the data register. It is also used in input/output operations. It is also used with AX register along with DX for multiply and divide operations involving large values.

What is the EAX register used for?

EAX,AX,AH,AL : Called the Accumulator register. It is used for I/O port access, arithmetic, interrupt calls, etc…

What is the purpose of the EBP register?

A frame pointer (the ebp register on intel x86 architectures, rbp on 64-bit architectures) contains the base address of the function’s frame. The code to access local variables within a function is generated in terms of offsets to the frame pointer.

What does EAX mean?

general purpose register
It stands for a general purpose register. The 16 bit AX register can be addressed as AH (high byte) and AL (low byte). The EAX register is the 32 bit version of the AX register.

What is ESP vs EBP?

2 Answers. ESP is the current stack pointer. EBP is the base pointer for the current stack frame. When you call a function, typically space is reserved on the stack for local variables.

Is EBP a general purpose register?

Compilers still sometimes use EBP, and functions that use EBP to maintain a frame pointer are called “frame based.” Functions that are not frame based can use EBP as another general purpose register and use it for calculations just like any other register.

What does R stand for in Rax?

At the same time Intel was introducing additional, general purpose registers. Using a common industry naming convention for general purpose register, the letter R, followed by a number was an easy decision.

Why is the ECX register used during an increment?

The original value of the i variable (before incrementing) can possibly be used again in the same expression so it is saved to the ecx register and the result of the postfix increment operation is stored to the variable on the stack immediately ( mov [ebp+var_4], eax ). It does not matter that the value in ecx is not used later.

What kind of registers are used in multiplication?

For example, in multiplication operation, one operand is stored in EAX or AX or AL register according to the size of the operand. BX is known as the base register, as it could be used in indexed addressing. CX is known as the count register, as the ECX, CX registers store the loop count in iterative operations. DX is known as the data register.

Which is register stores the starting address of the code segment?

A 16-bit Code Segment register or CS register stores the starting address of the code segment. Data Segment − It contains data, constants and work areas. A 16-bit Data Segment register or DS register stores the starting address of the data segment. Stack Segment − It contains data and return addresses of procedures or subroutines.

Why do you need Inc and DEC for loop control?

You need INC / DEC for various purposes, the most common being loop control. Many loops involved doing “multi-precision arithmetic” (e.g, 16 bits or more!)