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.
Example –
Assumptions – Assume that there are 4 blocks in memory addresses 0500, 0501, 0502, 0503.
Algorithm –
- 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
Program –
| MEMORY ADDRESS |
MNEMONICS |
COMMENTS |
| 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 |
Explanation –
- 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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Last Updated :
22 May, 2018
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