What is ah in assembly language?

What is ah in assembly language?

al and ah are the 8-bit, “char” size registers. al is the low 8 bits, ah is the high 8 bits. They’re pretty similar to the old 8-bit registers of the 8008 back in 1972.

What is AH 4ch assembly language?

mov ah,4ch is the first line of assembler code. The value 4C in hexadecimal is stored in the register AH. int 21h is the second line of assembler code. The software interrupt 21h is called. This interrupt, when given the value of 4ch in AH (as is the case here), causes the program to exit immediately.

What does .stack 100h mean?

stack 100h reserves 100h bytes for stack. org 100h sets the current address to 100h, that is the address the assembler is assuming. Note that stack 100h applies to exe files, it’s going to be written in a header so the loader provides that much stack for you.

What is cmp al 0Dh in assembly language?

0Dh is the hexadecimal constant for the Carriage Return character in ASCII, often abbreviated CR. 0Ah is the hexadecimal constant for the Line Feed character in ASCII, often abbreviated LF. 24h is the hexadecimal constant for the ‘$’ character in ASCII.

What is EAX and EBX?

The EAX, EBX, ECX, EDX, EBP, EDI, and ESI registers are all 32-bit general-purpose registers, used for temporary data storage and memory access. https://web.archive.org/web/20191114093028/https://gerardnico.com/computer/cpu/register/general. Some of CPU instructions modify specific registers.

What is Lea command?

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 is DL in assembly language?

So you can access the whole 32 bit register as EDX (when in protected mode) and the lower 16 bit register as DX. Now this 16 bit part (DX) is further divided into two parts: the upper 8 bit are accessed as DH, the lower 8 bit as DL.

What is the use of ORG 100h?

It sets the current address during assembly to be 100h. That’s all it is. A simple assignment.