; This patch causes the CCP of a cp/m 2.x system to look on drive A ; when you are logged into a drive other than A and call for a .COM ; file that does not exist on that drive. Giving an explicit drive ; reference overrides this feature, so that you can always force ; the file to be loaded from a specific drive. ; msize equ 60 ; set this to your nominal system size ; cpmb equ (msize-20)*1024+3400h ; start of CCP in given sys size ; org cpmb+6dbh jz patch ; replaces "jz cpmb+76bh" ; org cpmb+7f2h ; replaces an unused area of NOP's patch: lxi h,cpmb+7f0h ; get drive from current command ora m ; accum was 0 on entry, so this fetches drive jnz cpmb+76bh ; command has explicit drive...give error inr m ; force explicit reference to drive A lxi d,cpmb+7d6h ; we need de set up when we jmp cpmb+6cdh ; re-enter ccp ; end