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Author | SHA1 | Date |
---|---|---|
CrazyEttin | 5be8fad422 |
48
README.MD
48
README.MD
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@ -1,9 +1,9 @@
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EttinOS
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=======
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EttinOS is a minimalist 16-bit DOS-like hobbyist operating system for
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the IBM Personal Computer and compatible machines. Its git repository
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can be found at https://ahti.space/git/crazyettin/EttinOS and that of
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EttinOS is a minimalist 16-bit hobbyist disk operating system for the
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IBM Personal Computer and compatible machines. Its git repository can be
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found at https://ahti.space/git/crazyettin/EttinOS and that of
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EttinOS-extra, a collection of programs for the system, at
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https://ahti.space/git/crazyettin/EttinOS-extra.
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@ -40,12 +40,13 @@ overwrites the cursor location and the erase (=tab) key erases it. The
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space and backspace keys move the cursor.
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EttinOS assigns the drives letters from A to D and uses the FAT12 file
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system. The hidden and total sectors entries of the BIOS parameter
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block, the entire extended BIOS parameter block, file attributes, and
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the file access date are not supported and are ignored if present: as a
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result disk labels and subdirectories are not supported. Drive letters
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and file names are case-insensitive and the latter follow the 8.3
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format. Text files use CRLF line endings.
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system. The BIOS parameter block sections for hidden and total sectors,
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the entire extended BIOS parameter block, and the directory entry
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sections for file attributes, creation date and time, and access date
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are not supported and are ignored if present: as a result disk labels
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and subdirectories are not supported. Drive letters and file names are
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case-insensitive and the latter follow the 8.3 format. Text files use
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CRLF line endings.
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Drives and files are specified as ([A-D]:) and ([A-D]:)FILENAME.EXT
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respectively. Specifying the current drive, indicated in the prompt, is
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@ -53,11 +54,11 @@ optional.
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A command can be followed by arguments separated from eachother and the
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command with spaces. Extra spaces are ignored. Commands other than
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changing the drive are stored as external programs: the command for a
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program is its file specification without the extension.
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changing the current drive are stored as external programs: the command
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for a program is its file specification without the extension.
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Commands included in EttinOS:
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* [A-D]:: Change the drive.
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* [A-D]:: Change the current drive.
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* ECHO: Print a message. Syntax: ECHO Message to be printed
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* HELLO: Print "Hello world!".
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* LIST: Print a list of the files on a drive. Syntax: LIST DRIVE
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@ -80,7 +81,7 @@ has finished running.
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System calls:
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* Interrupt 0x20: Return to the shell.
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* Interrupt 0x21: Input and output:
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* Interrupt 0x21: String operations:
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* AH = 0x0: Print a string ending in a null from SI.
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* AH = 0x1: Read a string ending in a null of at most AL
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characters to DI until a return.
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@ -88,8 +89,25 @@ System calls:
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CRLF.
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* AH = 0x3: Read a string ending in a null of at most AL
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characters to DI until a return and print a CRLF.
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* AH = 0x4: (Under construction) Convert a decimal string ending
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in a null at SI to a value in AL.
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* AH = 0x5: (Under construction) Convert a value in AL to a
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decimal string ending in a null at DI.
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* AH = 0x6: (Under construction) Convert a hexadecimal string
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ending in a null at SI to a value in AL.
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* AH = 0x7: (Under construction) Convert a value in AL to a
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hexadecimal string ending in a null at DI.
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* Interrupt 0x22: Disk operations:
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* AH = 0x0: Load a file named at SI as a string ending in a null
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* AH = 0x0: (Under construction) Load the directory of a drive
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named at SI as a string ending in a null to the offset
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BX and store the error codes in AL:
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* AL = 0x0: Succesful load
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* AL = 0x1: Drive not found
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* AL = 0x2: Unable to read disk
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* AH = 0x1: (Under construction) Store a directory at the offset
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BX to a drive named at SI as a string ending in a
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null.
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* AH = 0x2: Load a file named at SI as a string ending in a null
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to the offset BX and store the file size in CX and the
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error codes in AL:
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* AL = 0x0: Succesful load
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@ -97,7 +115,7 @@ System calls:
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* AL = 0x2: Unable to read disk
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* AL = 0x4: File or command not found
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* AL = 0x8: Not enough memory
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* AH = 0x1: Save a file (under construction).
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* AH = 0x3: (Under construction) Save a file.
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Known bugs
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----------
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@ -16,8 +16,8 @@ push di
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;Store the current drive and offset
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mov word [.pointer], bx
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mov dl, byte [drive]
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mov byte [.drive], dl
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mov dl, byte [curdrive]
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mov byte [drive], dl
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;Change the drive if needed
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;Check for a drive specification
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@ -53,7 +53,7 @@ mov cx, 0x0
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jmp .done
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;Change the drive
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.contchdrive:
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mov [.drive], dl
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mov [drive], dl
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;Move to the file name
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add si, 0x2
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@ -112,7 +112,7 @@ pop ax
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;Load the disk description table
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;Set the source
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mov dl, [.drive]
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mov dl, [drive]
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mov ch, 0x0
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mov dh, 0x0
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mov cl, 0x1
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@ -136,48 +136,48 @@ jmp .done
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;Store the disk values used for the rest of the call
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.storevalues:
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mov ax, [buffer + 0xb]
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mov [.sectorsize], ax
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mov [sectorsize], ax
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mov al, [buffer + 0xd]
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mov [.clustersize], al
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mov [clustersize], al
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mov ax, [buffer + 0xe]
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mov [.reservedsectors], ax
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mov [reservedsectors], ax
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mov al, [buffer + 0x10]
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mov [.fats], al
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mov [fats], al
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mov ax, [buffer + 0x11]
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mov [.rootentries], ax
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mov [rootentries], ax
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mov ax, [buffer + 0x16]
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mov [.sectorsperfat], ax
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mov [sectorsperfat], ax
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mov ax, [buffer + 0x18]
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mov [.sectorspertrack], ax
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mov [sectorspertrack], ax
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mov ax, [buffer + 0x1a]
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mov [.heads], ax
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mov [heads], ax
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;Calculate and store variables not found in the BPB
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;Start of the root
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mov ah, 0x0
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mov al, [.fats]
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mul word [.sectorsperfat]
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add ax, [.reservedsectors]
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mov [.rootstart], ax
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mov al, [fats]
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mul word [sectorsperfat]
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add ax, [reservedsectors]
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mov [rootstart], ax
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;Size of the root in sectors
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mov ax, [.rootentries]
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mov ax, [rootentries]
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mov dx, 0x20
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mul dx
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mov dx, 0x0
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div word [.sectorsize]
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mov [.rootsectors], ax
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div word [sectorsize]
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mov [rootsectors], ax
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;Start of data
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add ax, [.rootstart]
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mov [.datastart], ax
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add ax, [rootstart]
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mov [datastart], ax
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;Load the root
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;Set the source
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mov ax, [.rootstart]
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mov ax, [rootstart]
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;Set the destination
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mov si, buffer
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mov bx, si
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;Set the size
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mov cx, [.rootsectors]
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mov cx, [rootsectors]
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;Store the source and the loop counter in the stack
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.loadrootsector:
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push ax
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@ -194,7 +194,7 @@ pop cx
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pop ax
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;Set the next sector
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add ax, 0x1
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add bx, word [.sectorsize]
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add bx, word [sectorsize]
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;Load the next sector
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loop .loadrootsector
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@ -202,7 +202,7 @@ loop .loadrootsector
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;Set DI to the root
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mov di, buffer
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;Set the number of root entries
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mov cx, word [.rootentries]
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mov cx, word [rootentries]
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;Set the entry pointer
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mov ax, 0x0
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;Store the loop counter in the stack
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@ -238,8 +238,8 @@ cmp word [di + 0x13], 0x0
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jne .sizerror
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;Get the cluster size in bytes
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mov ah, 0x0
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mov al, [.clustersize]
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mul word [.sectorsize]
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mov al, [clustersize]
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mul word [sectorsize]
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mov bx, ax
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;Store the file size
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mov ax, [di + 0x11]
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@ -267,12 +267,12 @@ jmp .done
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mov ax, [di + 0xf]
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mov [.cluster], ax
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;Set the source
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mov ax, [.reservedsectors]
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mov ax, [reservedsectors]
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call .calcsource
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;Set the destination
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mov bx, buffer
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;Set the size
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mov ax, [.sectorsperfat]
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mov ax, [sectorsperfat]
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;Load the FAT
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mov ah, 0x2
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int 0x13
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@ -282,13 +282,13 @@ int 0x13
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;Set the source
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mov ax, word [.cluster]
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sub ax, 0x2
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mul byte [.clustersize]
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add ax, [.datastart]
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mul byte [clustersize]
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add ax, [datastart]
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;Set the destination
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mov bx, word [.pointer]
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;Set the size
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mov ch, 0x0
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mov cl, byte [.clustersize]
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mov cl, byte [clustersize]
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;Store the loop counter in the stack
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.loadsector:
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push cx
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@ -303,7 +303,7 @@ int 0x13
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pop ax
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;Set the next sector
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add ax, 0x1
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add bx, word [.sectorsize]
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add bx, word [sectorsize]
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;Load the loop counter from the stack
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pop cx
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;Load the next sector
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@ -335,8 +335,8 @@ jge .success
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;Store the address of the next cluster
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mov word [.cluster], ax
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;Set the destination of the next cluster
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mov ax, [.sectorsize]
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mul word [.clustersize]
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mov ax, [sectorsize]
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mul word [clustersize]
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add word [.pointer], ax
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;Load the next cluster
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jmp .loadcluster
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@ -362,18 +362,6 @@ mov ah, 0x0
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iret
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;Data
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.drive db 0x0
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.sectorsize dw 0x0 ;bytes
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.clustersize db 0x0 ;sectors
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.reservedsectors dw 0x0
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.fats db 0x0
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.rootentries dw 0x0
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.sectorsperfat dw 0x0
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.sectorspertrack dw 0x0
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.heads dw 0x0
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.rootstart dw 0x0
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.rootsectors dw 0x0
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.datastart dw 0x0
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.file times 0xb db 0x20
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.size dw 0x0
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.cluster dw 0x0
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@ -454,21 +442,21 @@ push bx
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mov bx, ax
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;Calculate the sector
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mov dx, 0x0
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div word [.sectorspertrack]
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div word [sectorspertrack]
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add dl, 0x1
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mov cl, dl
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;Load the logical sector from BX
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mov ax, bx
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;Calculate the head and cylinder
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mov dx, 0x0
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div word [.sectorspertrack]
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div word [sectorspertrack]
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mov dx, 0x0
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div word [.heads]
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div word [heads]
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mov dh, dl ;Head
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mov ch, al ;Cylinder
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;Load the drive number
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mov dl, byte [.drive]
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mov dl, byte [drive]
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;Load BX and AX from the stack
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pop bx
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|
|
|
@ -40,7 +40,7 @@ stosb
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;Load
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load:
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mov bx, stack + 0x100
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mov ah, 0x0
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mov ah, 0x2
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int 0x22
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;Check for errors
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cmp al, 0x0
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|
|
|
@ -21,7 +21,7 @@ je readln
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iret
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;Disk operations
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int0x22:
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cmp ah, 0x0
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cmp ah, 0x2
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je loadf
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;To do: savef
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iret
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|
@ -50,9 +50,10 @@ mov [0x82], ax
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mov [0x86], ax
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mov [0x8a], ax
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;Store the boot drive number and set the drive letter
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mov [drive], dl
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call setdriveletter
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;Store the boot drive number as the current drive and set the current
|
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;drive letter
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mov [curdrive], dl
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call setcurdriveletter
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|
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;Print a welcome message
|
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mov si, welcomemsg
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|
@ -67,8 +68,8 @@ mov sp, 0x0
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sti
|
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|
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;Prompt for and read a command
|
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;Print the drive letter
|
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mov si, driveletter
|
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;Print the current drive letter
|
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mov si, curdriveletter
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mov ah, 0x0
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int 0x21
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;Print a prompt
|
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|
@ -85,26 +86,24 @@ int 0x21
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cmp byte [input], 0x0
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jz shell
|
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|
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;Check for a drive change command
|
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;Set SI at the command
|
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;Set SI at input
|
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mov si, input
|
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;Ignore leading spaces
|
||||
call ignoreleading
|
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;Check
|
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|
||||
;Check for a current drive change command
|
||||
cmp byte [si + 0x1], ":"
|
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jne extract
|
||||
cmp byte [si + 0x2], 0x0
|
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je changedrive
|
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je changecurdrive
|
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cmp byte [si + 0x2], 0x20
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je changedrive
|
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je changecurdrive
|
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|
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;Extract the specification of the program file
|
||||
extract:
|
||||
;Set SI at input and DI at program
|
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mov si, input
|
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;Set DI at program
|
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mov di, program
|
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;Ignore leading spaces
|
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call ignoreleading
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;Initialise program with spaces
|
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mov cx, 0xe
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mov al, 0x20
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|
@ -142,21 +141,28 @@ rep movsb
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|||
;Load the program
|
||||
mov bx, 0x3000
|
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mov si, program
|
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mov ah, 0x0
|
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mov ah, 0x2
|
||||
int 0x22
|
||||
;Check for errors
|
||||
cmp al, 0x0
|
||||
jne shell
|
||||
;Pass the drive and command tail to the program
|
||||
mov dl, [drive]
|
||||
;Pass the current drive and command tail to the program
|
||||
mov dl, [curdrive]
|
||||
pop si
|
||||
call ignoreleading
|
||||
;Execute the program
|
||||
jmp 0x3000
|
||||
|
||||
;Change the drive
|
||||
;Print a command error message and return to the shell
|
||||
cmderror:
|
||||
mov si, cmderrormsg
|
||||
mov ah, 0x2
|
||||
int 0x21
|
||||
jmp shell
|
||||
|
||||
;Change the current drive
|
||||
;Get the BIOS equipment list
|
||||
changedrive:
|
||||
changecurdrive:
|
||||
int 0x11
|
||||
;Get the number of floppy drives
|
||||
times 0x6 shr ax, 0x1
|
||||
|
@ -184,33 +190,44 @@ int 0x21
|
|||
jmp shell
|
||||
;Change the drive
|
||||
contchdrive:
|
||||
mov [drive], dl
|
||||
call setdriveletter
|
||||
mov [curdrive], dl
|
||||
call setcurdriveletter
|
||||
jmp shell
|
||||
|
||||
;Print a command error message and return to the shell
|
||||
cmderror:
|
||||
mov si, cmderrormsg
|
||||
mov ah, 0x2
|
||||
int 0x21
|
||||
jmp shell
|
||||
;Welcome message
|
||||
welcomemsg db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0x0
|
||||
|
||||
;Data
|
||||
welcomemsg db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0x0
|
||||
drive db 0x0
|
||||
driveletter db "?:", 0x0
|
||||
;Drive stuff
|
||||
curdrive db 0x0
|
||||
driveletters db "AaBbCcDd"
|
||||
prompt db "> ", 0x0
|
||||
input times 0x4c db 0x0
|
||||
program times 0xf db 0x0
|
||||
extension db ".BIN", 0x0
|
||||
cmderrormsg db "File or command not found", 0x0
|
||||
driverrormsg db "Drive not found", 0x0
|
||||
|
||||
;Shell
|
||||
curdriveletter db "?:", 0x0
|
||||
prompt db "> ", 0x0
|
||||
input times 0x4c db 0x0
|
||||
program times 0xf db 0x0
|
||||
extension db ".BIN", 0x0
|
||||
cmderrormsg db "File or command not found", 0x0
|
||||
driverrormsg db "Drive not found", 0x0
|
||||
|
||||
;Disk parameters
|
||||
drive db 0x0
|
||||
sectorsize dw 0x0 ;bytes
|
||||
clustersize db 0x0 ;sectors
|
||||
reservedsectors dw 0x0
|
||||
fats db 0x0
|
||||
rootentries dw 0x0
|
||||
sectorsperfat dw 0x0
|
||||
sectorspertrack dw 0x0
|
||||
heads dw 0x0
|
||||
rootstart dw 0x0
|
||||
rootsectors dw 0x0
|
||||
datastart dw 0x0
|
||||
|
||||
;***
|
||||
|
||||
;Set the drive letter
|
||||
setdriveletter:
|
||||
setcurdriveletter:
|
||||
|
||||
;Set the drive number and letter counters
|
||||
mov dh, 0x0
|
||||
|
@ -227,7 +244,7 @@ jmp .checkdrive
|
|||
;Set the drive letter
|
||||
.set:
|
||||
mov al, [si]
|
||||
mov byte [driveletter], al
|
||||
mov byte [curdriveletter], al
|
||||
|
||||
;Return
|
||||
ret
|
||||
|
|
Loading…
Reference in New Issue