String instructions in 8086 microprocessors are used to operate on groups of sequential bytes or words in memory. They include REP/REPE/REPZ to repeatedly perform an instruction until CX reaches 0 or the zero flag is set, MOVS/MOVSB/MOVSW to move a string between memory locations, INS/INSB/INSW to input a string from an I/O port to memory, and OUTS/OUTSB/OUTSW to output a string from memory to an I/O port. Other string instructions are COMS/COMPSB/COMPSW to compare strings, SCAS/SCASB/SCASW to scan and compare a string, and LODS/LODSB/