diff --git a/README.md b/README.md
index 07fb5a3..b394707 100644
--- a/README.md
+++ b/README.md
@@ -17,36 +17,27 @@ On a 8080, there are no segments, the addresses are as displayed.
 On on the 8086, a single segment with a value of 0x0100 is assumed.
 This implies that the first 4k of memory are not used.
 
-The BIOS and FDOS may be recompiled for starting at a lower address, in this case,
+The BIOS and BDOS may be recompiled for starting at a lower address, in this case,
 the minimum memory requirement may be less than 64k.
 
-|Start|Size|Function|
-|--|--|--|
-|0xF800|2k|BIOS / hw drivers|
-|0xF000|2k|BDOS|
-|...|...|BDOS data area, disk deblocking buffers|
-|SP|var|Stack, growing down|
-|...|...|Free memory|
-|...|var|Heap, growing up|
-|0x0100|var|Transient Program Area|
+|Start |Size     |Function|
+|------|---------|--------|
+|0xF800|2k       |BIOS / hw drivers|
+|0xF000|2k       |BDOS|
+|...   |...      |BDOS data area, disk deblocking buffers|
+|SP    |var      |Stack, growing down|
+|...   |...      |Free memory|
+|...   |var      |Heap, growing up|
+|0x0100|var      |Transient Program Area|
 |0x0080|128 bytes|Command line and disk buffer|
 |0x0008|120 bytes|BIOS data area|
-|0x0000|8 bytes|BDOS data area|
+|0x0005|3 bytes  |Jump code for BDOS|
+|0x0004|1 bytes  |default drive for BDOS|
+|0x0003|1 bytes  |may be used as iobyte by BIOS|
+|0x0000|3 bytes  |Jump to BIOS warm boot entry point / program exit|
 
 ## Application program interface
 
 It is using the `call 5` convention with CP/M compatible syscall numbers.
 
 File I/O is done via FCB blocks.
-
-## Zero page
-
-|Offset|Size|Usage|
-|--|--|--|
-|0x00|3 bytes|warm reboot/program exit jump instruction|
-|0x03|byte|unused (would be iobyte)|
-|0x04|byte|default drive|
-|0x05|3 bytes|syscall jump instruction|
-|0x08|120 bytes|interrupts and work area for BIOS|
-|0x80|byte|length of command line|
-|0x81|127 bytes|command line with $length bytes plus a trailing 0x0D|