8086 program to transfer a block of 4 bytes by using string instructions
Problem – Write a program to transfer a block of 4 bytes, starting address is 0500 and transfer the block at address 0600 by using string instructions.
Assumptions – Assume that there are 4 blocks in memory addresses 0500, 0501, 0502, 0503.
- Assign value 500 in SI and 600 in DI
- Assign the value 0000 H to AX
- Move the content of AX in DS
- Move the content of AX in ES
- Assign the value 0004 H to CX
- Clear the directional flag
- Repeat until CX=0, Move string block
- Halt of the program
|0400||MOV SI, 500||SI <- 500|
|0403||MOV DI, 600||DI <- 600|
|0406||MOV AX, 0000||AX <- 0000|
|0409||MOV DS, AX||DS <- AX|
|040B||MOV ES, AX||ES <- AX|
|040D||MOV CX, 0004||CX <- 0004|
|0410||CLD||CLEAR DIRECTIONAL FLAG|
|0411||REP||REPEAT UNTIL CX=0|
|0412||MOVSB||MOVE THE BLOCK|
|0413||HLT||END OF THE PROGRAM|
- MOV SI, 500 assigns 500 to SI
- MOV DI, 600 assigns 600 to DI
- MOV AX, 00 assign 0000 to AX register
- MOV DS, AX moves the content of AX to DS segment
- MOV ES, AX moves the content of AX to ES segment
- MOV CX, 0004 assign 0000 to CX register
- CLD clear the directional flag
- REP repeat until CX=0
- MOVSB move string block
- HLT stops the execution of the program.
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