Question

Write an inline assembly program that initialized a 100 byte area of memory using the STOS instruction.

Answer 1

ASSEMBLY PROGRAM:---

MOV AL,0 ------>moves the value zero to AL register

LEA DI,BUFFER ------> loads effective address

MOV CX,100 ----->moves value 100 to CX register

CLD ----->clears direction flag

REP STOS BUFFER ------>repeats the above steps until count is zero

AL: Low byte of AX register

MOV: Command used to move data between registers and memory.

LEA: Load effective address.

DI : it is the destination index ,it is a pointer used to compare current character in string .

BUFFER : sequence of bytes.

CX : it is a 16 bit register.

CLD : It clears the direction flag. Direction flag is used to decide in which direction instructions work when used with REP command.

REP: This is similar to loops in java,but in this it is used to repeat all the instructions until count is 0.

STOS: it is used to store data(in bytes,word etc)  from registers(AX,BX,CX) into specific memory locations(operands).The address is read from either  ES:EDI or the ES:DI registers (depending on the address-size attribute of the instruction, 32 or 16, respectively).