1. Princess Sumaya Univ. Computer Engineering Dept. Chapter 9:

2. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 1 / 10 String Operands String Operands Defaults Byte, Word or Double Element Size DS:SI Points to Source String ES:DI Points to Destination String Register Use is Limited to AL & AX Auto Increment or Decrement of the Index (Pointer)

3. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 2 / 10 String Operations String Transfer Operations MOVS (Byte or Word) Memory DS 0000 0001 SI 0002 0003 0004 0005Memory ES 0000 0001 0002 0003 DI 0004 0005

4. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 3 / 10 String Operations String Transfer Operations LODS (Byte or Word) Memory DS 0000 0001 SI 0002 0003 0004 0005Memory ES 0000 0001 0002 0003 DI 0004 0005 AL

5. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 4 / 10 String Operations String Transfer Operations STOS (Byte or Word) Memory DS 0000 0001 SI 0002 0003 0004 0005Memory ES 0000 0001 0002 0003 DI 0004 0005 AL

6. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 5 / 10 Repeated String Operations Repeated String Transfers REP, REPZ, REPNZ (REPE, REPNE) Example: Memory DS 0000 0001 SI 0002 0003 0004 0005Memory ES 0000 0001 0002 DI 0003 0004 0005

7. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 6 / 10 Repeated String Operations Example: Copy String Memory DS 0000 0001 SI 0002 0003 0004 0005 ES 0000 0001 DI 0002 0003 0004 0005

8. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 7 / 10 Repeated String Operations Example: Convert to Lower Case Memory DS 0000 0001 SI 0002 0003 0004 0005 ES 0000 0001 DI 0002 0003 0004 0005

9. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 8 / 10 Repeated String Operations Example: B[i] = – A[i] Memory DS 0000 0001 SI 0002 0003 0004 0005 ES 0000 0001 DI 0002 0003 0004 0005

10. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 9 / 10 String Comparison Compare Two Strings CMPS (Byte or Word) Example:Find the First Mismatch Memory DS 0000 0001 SI 0002 0003 0004 0005 ES 0000 0001 DI 0002 0003 0004 0005

11. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. 10 / 10 String Search Scan Destination String SCAS (Byte or Word) Example:Search for the Letter a Memory DS 0000 0001 SI 0002 0003 0004 0005 ES 0000 0001 DI 0002 0003 0004 0005

12. Princess Sumaya University 22342 – Computer Org. & Assembly Lang. Computer Engineering Dept. Chapter 9