Strings

When dealing with strings the source string is normally ESI and the destination is EDI


Direction Flag:
  Set the flag: STD
  Clear the flag: cld
  
  This flag will change what direction the string instruction is going to go through the string. left to right or right to left
  If the flag is set it will go from highest to lowest memeory address AKA Right to Left
  If the flag is not set it will go from lowest to highest memory AKA Left to Right


REP:
  This is used to repeat strings operations
  it will continue to run until CX is set to 0 and check if the ZF flag is set
  This will also DEC -1 to CX each time it runs. Normally the length of a string is in ecx
  
  REPE: 
    This will do exactly the same as REP exept it WILL set the ZF flag if any byte does not match on each compare
    This is usefull for conditonal jumps right after
    
MOVSB:
  This will move the byte from ESI into EDI overwriting what was in EDI
  
CMPSB:
  This will compare byte by byte form ESI to EDI and if a match is found the ZF flag is set, if not nothing else happens