Which term maintains the source index for string operations?

Which term maintains the source index for string operations?

• A. Extended Instruction Pointer (EIP)
• B. Extended Source Index (ESI)
• C. Extended Stack Pointer (ESP)
• D. Extended Base Pointer (EBP)

Answer: (B)

In string operations, one register holds the address of the data being read (the source), while another holds the address where data will be written (the destination). The register that acts as the source pointer in 32-bit x86 is the Extended Source Index, abbreviated ESI. It originates from SI and is used by instructions like MOVS and CMPS to fetch data from the source memory location. The destination pointer is the Extended Destination Index (EDI). Other registers mentioned serve different roles: EIP is the instruction pointer, ESP is the stack pointer, and EBP is the base (frame) pointer. So Extended Source Index (ESI) is the term that maintains the source index for string operations.

In string operations, one register holds the address of the data being read (the source), while another holds the address where data will be written (the destination). The register that acts as the source pointer in 32-bit x86 is the Extended Source Index, abbreviated ESI. It originates from SI and is used by instructions like MOVS and CMPS to fetch data from the source memory location. The destination pointer is the Extended Destination Index (EDI). Other registers mentioned serve different roles: EIP is the instruction pointer, ESP is the stack pointer, and EBP is the base (frame) pointer. So Extended Source Index (ESI) is the term that maintains the source index for string operations.