INT 21 - European MSDOS 4.0 - "FREEZE" - STOP A PROCESS
AH = 81h
BX = flag (00h freeze command subtree, 01h only specified process)
CX = Process ID of head of command subtree
Return: CF clear if successful
CF set on error
AX = error code (no such process)
Desc:   temporarily suspend a process or a process and all of its children
Note:   if BX=0001h, this call will not return until the process is actually
frozen, which may not be until after it unblocks from an I/O
SeeAlso: AH=89h,AX=8E00h,INT 15/AX=101Dh

See also: 2182

2181 - European MSDOS 4.0 - "FREEZE" - STOP A PROCESS