=== Structure of a utility ROM ===
Each ROM is 16KB and has the following structure:
{|
|-
| ''Offset (Hex)''
| ''Count''
| ''Description''
|-
| &100
| 256
| Directory (note 1)
|-
| &200
| &3e00
| Data area for files.
|}
Each directory entry has the following structure:
{|
|-
| ''Offset (Hex)''
| ''Count''
| ''Description''
|-
| 0
| 8
| Filename (note 2)
|-
| 8
| 1
| ? (unknown &20)
|-
| 9
| 2
| address in ROM for start of data for file (note 3)
|-
| 11
| 2
| length in bytes of file
|-
| 14
| 2
| (unknown) &feff
|}
Notes:
1. Up to 16 files can be defined. Each file takes 1 entry. Unused entries are filled with &FF.
2. Filename is in upper case, 8 characters long, padded with spaces. '.COM' extension is assumed when accessed.
3. ROM starts at &c000. Therefore &c200 is the start of the first file.
[[Category:Operating System]][[Category:CP/M]]