ED: Gotten l (list) working, need to work more on d (delete) as there's a bug with deleting lines that are not line 1.

Makefile

@@ -15,7 +15,7 @@ $(BUILD_DIR)/crawos.iso: floppy_image
 # Floppy image
 # Fat12
 floppy_image: $(BUILD_DIR)/crawos.img
-$(BUILD_DIR)/crawos.img: bootloader kernel
+$(BUILD_DIR)/crawos.img: bootloader kernel check-fat83
 	mkdir -p disk_images
 	dd if=/dev/zero of=$(BUILD_DIR)/crawos.img bs=512 count=2880 # Use dd to make a disk image
 	mkfs.fat -F 12 -n "CRAWOS" $(BUILD_DIR)/crawos.img # Format the disk image with fat12
@@ -36,6 +36,11 @@ $(BUILD_DIR)/kernel.bin:
 	mkdir -p disk_images
 	$(ASM) $(SRC_DIR)/kernel/kernel.asm -f bin -o $ $(BUILD_DIR)/kernel.bin
 
+check-fat83:
+	@echo "Checking filenames for FAT 8.3 compliance..."
+	@find ./data -type f | awk -F/ '{print $$NF}' | \
+	awk -F. 'length($$1)>8 || length($$2)>3 || NF>2 {print "Invalid FAT 8.3 filename:", $$0; bad=1} END{exit bad}'
+
 # Clean
 clean:
 	rm -f disk_images/*

data/README.md

@@ -1,9 +1,14 @@
-Kernel written in Assmebly
+# What is this?
-I'm using a modified JazzOS Bootloader
+This is a simple implementation of a computer kernel
+written in pure x86 assembly with features including 
+- Read/Write disk operations
+- The ability to boot from the BIOS using the JazzOS Bootloader
+- A modified MikeOS BASIC interpreter
+- A functional POSIX inspired CLI
 
-Commands:
+# Commands
-CAT
+- CAT <filename>: outputs the contents of the file.
-HELP
+- LS: outputs a list of files on the system .
-CLEAR
+- CLEAR: clears the screen.
-REBOOT
+- REBOOT: or esc reboots the system
-PONG
+- BAS <filename>: runs a basic script.

data/hello.bas

@@ -1,2 +1,5 @@
-PORT OUT 80 5
+PRINT "Hello, what is your name?"
+INPUT $1
+PRINT "Hello " ;
+PRINT $1
 END

data/test.asm

@@ -0,0 +1,2 @@
+X = 100
+PRINT X

data/var.cws

@@ -1 +0,0 @@
-x = 5

source/kernel/data.asm

@@ -26,7 +26,7 @@ ebr_system_id:              db 'FAT12   ' ; must be 8 bytes
 fat12_file_name: db '           ' ; 11 free bytes to store a filename in
 boot_message: db 'OK] Kernel successfully loaded!\n"HELP" to see a list of available commands\n', 0
 user_input: times 20 db 0
-prompt_length: db 20
+prompt_length: dw 20
 prompt: db 'sh > ', 0
 help_string: db 'HELP', 0
 clear_string: db 'CLEAR', 0
@@ -34,7 +34,8 @@ reboot_string: db 'REBOOT', 0
 basic_string: db 'BAS', 0
 cat_string: db 'CAT', 0
 ls_string: db 'LS', 0
-help_text: db 'This is for Cowards:\n"LS" to list the directory,\n"CAT" to output the contents of a file,\n"BAS" to run a basic script,\n"HELP" for this helpful text,\n"CLEAR" to clear the screen,\n"REBOOT" or esc to reboot\n', 0
+ed_string: db 'ED', 0
+help_text: db 'This is for Cowards:\n"LS" to list the directory,\n"CAT <filename>" to output the contents of a file,\n"BAS <filename>" to run a basic script,\n"HELP" for this helpful text,\n"CLEAR" to clear the screen,\n"REBOOT" or esc to reboot\n', 0
 basic_text: db 'BASIC PROGRAM BEGUN:\n', 0
 command_result_text: db 'You typed: ', 0
 unknown_command: db 'Error: Unkown Command..\n ', 0
@@ -47,12 +48,6 @@ file_not_found: db 'File not found\n', 0
 too_long_filename: db 'Filename too long for Fat12\n', 0
 file_found: db 'File found\n', 0
 loading_root: db 'Loading root diretory\n', 0
-read_only: db 'Read Only', 0 ; 1
-hidden:    db '  Hidden ', 0 ; 2
-system:    db '  System ', 0 ; 4
-volume:    db '  Volume ', 0 ; 8
-directory: db 'Directory', 0 ; 10
-archive:   db ' Archive ', 0 ; 20
 file_name_length: db 0
 file_cluster: dw 0
 file_length: dd 0

source/kernel/features/basic.asm

@@ -842,14 +842,14 @@ do_break:
 do_call:
 	call get_token
 	cmp ax, NUMBER
-	je .is_number
+	je .check_is_number
 
 	mov ax, 0
 	mov byte al, [token]
 	call get_var
 	jmp .execute_call
 
-.is_number:
+.check_is_number:
 	mov si, token
 	call string_cast_to_int
 
@@ -1325,7 +1325,7 @@ do_for:
 	cmp ax, NUMBER
 	jne .error
 
-.second_is_number:
+.second_check_is_number:
 	mov si, token					; Get target number
 	call string_cast_to_int
 	jmp .continue2
@@ -1625,7 +1625,7 @@ do_if:
 	je .equals_char
 
 	mov byte al, [token]
-	call is_letter
+	call check_is_letter
 	jc .equals_var
 
 	mov si, token				; Otherwise it's, eg 'X = 1' (a number)
@@ -1711,7 +1711,7 @@ do_if:
 .greater:
 	call get_token				; Greater than a variable or number?
 	mov byte al, [token]
-	call is_letter
+	call check_is_letter
 	jc .greater_var
 
 	mov si, token				; Must be a number here...
@@ -1736,7 +1736,7 @@ do_if:
 .less:
 	call get_token
 	mov byte al, [token]
-	call is_letter
+	call check_is_letter
 	jc .less_var
 
 	mov si, token
@@ -1950,8 +1950,9 @@ do_input:
 
 .number_var:
 	mov ax, .tmpstring			; Get input from the user
-	mov bx, 6
+	mov bx, 20
 	call keyboard_display_input
+	jc .end
 
 	mov ax, .tmpstring
 	call string_length
@@ -1973,8 +1974,6 @@ do_input:
 	call os_print_newline
 
 	jmp mainloop
-
-
 .string_var:
 	mov ax, 128
 	mul bx
@@ -1987,8 +1986,9 @@ do_input:
 
 	jmp mainloop
 
-
+	.tmpstring	times 20 db 0
-	.tmpstring	times 6 db 0
+.end
+	ret
 
 
 ; -----------------------------------------------------------
@@ -2636,7 +2636,7 @@ do_peekint:
 	cmp ax, NUMBER
 	jne .error
 	
-.address_is_number:
+.address_check_is_number:
 	mov si, token
 	call string_cast_to_int
 	jmp .load_data
@@ -3770,14 +3770,14 @@ do_string:
 	call get_token			; Now there should be a number
 	
 	cmp ax, NUMBER
-	je .third_is_number
+	je .third_check_is_number
 	
 	cmp ax, VARIABLE
 	je .third_is_variable
 	
 	jmp .error
 	
-.third_is_number:	
+.third_check_is_number:	
 	mov si, token
 	call string_cast_to_int
 	jmp .got_number	
@@ -3984,7 +3984,7 @@ get_token:
 	cmp al, ' '
 	je .newline
 
-	call is_number
+	call check_is_number
 	jc get_number_token
 
 	cmp al, '"'
@@ -4030,7 +4030,7 @@ get_number_token:
 	je .done
 	cmp al, ' '
 	je .done
-	call is_number
+	call check_is_number
 	jc .fine
 
 	mov si, err_char_in_num
@@ -4153,7 +4153,7 @@ get_string_token:
 
 .is_not_string:
 	mov byte al, [token]
-	call is_letter
+	call check_is_letter
 	jc .is_var
 
 	mov ax, UNKNOWN
@@ -4164,37 +4164,6 @@ get_string_token:
 	ret
 
 
-; ------------------------------------------------------------------
-; Set carry flag if AL contains ASCII number
-
-is_number:
-	cmp al, 48
-	jl .not_number
-	cmp al, 57
-	jg .not_number
-	stc
-	ret
-.not_number:
-	clc
-	ret
-
-
-; ------------------------------------------------------------------
-; Set carry flag if AL contains ASCII letter
-
-is_letter:
-	cmp al, 65
-	jl .not_letter
-	cmp al, 90
-	jg .not_letter
-	stc
-	ret
-
-.not_letter:
-	clc
-	ret
-
-
 ; ------------------------------------------------------------------
 ; Print error message and quit out
 

source/kernel/features/check.asm

@@ -0,0 +1,29 @@
+check_is_number:
+	cmp al, 48
+	jl .not_number
+	cmp al, 57
+	jg .not_number
+	stc
+	ret
+.not_number:
+	clc
+	ret
+
+check_is_letter:
+	cmp al, 65
+	jl .not_letter
+	cmp al, 122
+	jg .not_letter
+	cmp al, 90
+	jg .maybe_not_letter
+	stc
+	ret
+.maybe_not_letter:
+	cmp al, 97
+	jl .not_letter
+	stc
+	ret
+.not_letter:
+	clc
+	ret
+

source/kernel/features/cli.asm

@@ -1,5 +1,6 @@
 os_start_cli:
 	pusha
+
 	
 	call os_print_newline
 
@@ -11,6 +12,7 @@ os_start_cli:
 	mov ax, user_input
 
 	call keyboard_display_input
+	jc power_reboot
 	jmp os_read_cli
 
 
@@ -30,14 +32,14 @@ os_read_cli:
 	mov di, help_string
 	call os_compare_strings
 	cmp cl, 1
-	je help
+	je .help
 
 	; Clear screen
 	mov si, user_input
 	mov di, clear_string
 	call os_compare_strings
 	cmp cl, 1
-	je clear
+	je .clear
 
 	; Reboot
 	mov si, user_input
@@ -51,22 +53,29 @@ os_read_cli:
 	mov di, basic_string
 	call os_compare_strings
 	cmp cl, 1
-	je basic
+	je .basic
 
 	; Cat
 	mov si, user_input
 	mov di, cat_string
 	call os_compare_strings
 	cmp cl, 1
-	je cat
+	je .cat
 
     ; LS
 	mov si, user_input
 	mov di, ls_string
 	call os_compare_strings
 	cmp cl, 1
-	je ls
+	je .ls
 	
+    ;ED 
+	mov si, user_input
+	mov di, ed_string
+	call os_compare_strings
+	cmp cl, 1
+	je .ed
+
 	jmp .unkown
 
 .unkown:
@@ -77,24 +86,33 @@ os_read_cli:
 	jmp .finish
 
 .finish:
+	; Clear the user input
+	mov al, 0
+	mov cx, 20
+	mov di,user_input 
+	repe stosb
 	popa
 	call os_start_cli
 
-clear:
+.clear:
 	call os_set_text_mode
 	call os_read_cli.finish
 
-help:
+.help:
 	mov si, help_text
 	call os_print_string
 	call os_read_cli.finish
 
-basic:
+.basic:
 	call util_basic
 	call os_read_cli.finish
-cat:
+.cat:
    call util_cat
    call os_read_cli.finish
-ls:
+.ls:
    call util_ls
    call os_read_cli.finish
+.ed:
+   call util_ed
+   call os_read_cli.finish
+

source/kernel/features/disk.asm

@@ -171,6 +171,7 @@ disk_clear_output_buffer:
 ; OUT
 ; data_buffer: file contents
 ; TODO use predefined data for calculations
+; CX = 0 if failed to load
 disk_load_file:
    pusha
    call string_length ; cl = string length
@@ -227,13 +228,18 @@ disk_load_file:
 .file_not_found:
    mov si, file_not_found
    call os_print_string
-   jmp .done
+   jmp .done_fail
 .filename_too_long:
    mov si, too_long_filename
    call os_print_string
-   jmp .done
+   jmp .done_fail
+.done_fail:
+	popa
+	mov bx, 1
+	ret
 .done:
    popa
+	xor bx,bx
    ret
 
 ; Write data to file

source/kernel/features/keyboard.asm

@@ -15,6 +15,7 @@ os_read_input:
 
 ; AX = key pressed
 ; Returns straight away
+; carry flag is set when escape is pressed and data is returned straight away
 keyboard_check_key:
 	xor ax,ax
 	mov ah, 11h			; BIOS call to check for key
@@ -27,12 +28,13 @@ keyboard_check_key:
 ; IN:
 ; AX = output address
 ; BX = max length
-
+; OUT:
+; BX = 1 if escape is pressed
 keyboard_display_input:
 	pusha
 	mov di, ax
-	mov ax, bx
+	xor ax,ax
-	mov bx,20 
+	mov [prompt_length], bx
 
 	.check_key_pressed:
 		call os_read_input
@@ -55,16 +57,19 @@ keyboard_display_input:
 		jmp .check_key_pressed
 
 	.esc_key:
-		call power_reboot
+		popa
+		mov bx, 1
+		ret
 
 	.enter_key:
 		mov al, 0
 		stosb
 		popa
+		xor bx,bx
 		ret ; Return to the parent function (whatever that may be)
 
 	.backspace:
-		cmp bx, 20						; Cannot backspace if the cursor is at the start
+		cmp bx, [prompt_length]						; Cannot backspace if the cursor is at the start
 		jb .move_cursor_back			; then .move_cursor_back
 		jmp .check_key_pressed			; Else check the next key
 
@@ -87,6 +92,7 @@ keyboard_display_input:
 		mov ah, 0Eh
 		int 10h
 		jmp .check_key_pressed
+	.input_length db 0
 
 keyboard_get_cursor_pos:
 	ret

source/kernel/features/strings.asm

@@ -106,35 +106,42 @@ string_join:
 		ret
 
 ; ------------------------------------------------------------------------
-; TODO
+; Converts a string to an integer
-; Converts a null terminated string to an integer
 ; IN: SI = string location (max 5 chars, up to '65536')
-; OUT: AX = number
+; OUT: AX = number, DX = length of int string
 string_cast_to_int:
-	pusha
+	push cx
+	push bx
+	push dx
 	xor cx,cx
 	.loop:
 		xor ax,ax
 		lodsb
-		cmp al, 0
+
-		je .finish
+		; Exit if the character is not a number
-		sub al, 30h
+		cmp al,'0'
+		jl .finish
+		cmp al,'9'
+		jg .finish
+		
+		sub al, '0'
 		mov bx, ax
+
 		mov ax, 10
 		mul cx ; Multiple the current value by 10
 		add ax, bx ; Then add the new digit
 		mov cx, ax
 		jmp .loop
 	.finish:
-		mov [int_tmp], cx
+		mov ax,cx
-		popa
+		pop dx
-		mov ax, [int_tmp]
+		pop bx
+		pop cx
 		ret
 
 ; ------------------------------------------------------------------------
 ; IN:  AX = integer (unsigned)
 ; OUT: AX -> null-terminated string
-
 string_cast_from_int:
 	pusha
 	cld ; Write backwards

source/kernel/features/text.asm

@@ -55,10 +55,16 @@ text_print_raw:
 		je .space
 		cmp al, 0Ah	; When there's an NL or CR, do both, linux encodes files only with NL
 		je .new_line
+		cmp al, 09h ; TAB
+		je .tab
 		cmp al, 0Dh
 		je .repeat
 		int 10h
 		jmp .repeat
+	.tab:
+		mov al, ' '
+		int 10h
+		jmp .repeat
 	.space:
 		mov al, 20h
 		int 10h
@@ -129,6 +135,15 @@ os_set_text_mode:
 	mov dh, 0
 	mov dl, 0
 	int 10h
+
+text_newline:
+	pusha
+	mov ax,0E0Ah
+	int 10h
+	mov al,0Dh
+	int 10h
+	popa
+	ret
 
 	popa
 	ret

source/kernel/features/utils.asm

@@ -1,30 +1,33 @@
 util_cat:
-   pusha
+	pusha
 
-   call disk_clear_file_buffer
+	call disk_clear_file_buffer
-   mov si, user_input
+	mov si, user_input
-   ; TODO make this more consistent to account for double spaces
+	; TODO make this more consistent to account for double spaces
-   add si, 4   ; Move si to after 'CAT'
+	add si, 4   ; Move si to after 'CAT'
 
-   call disk_load_file
+	call disk_load_file
-   mov si, file_buffer
+	cmp bx, 1
-   mov cx, [file_length]
+	je .done
-   call text_print_raw
 
-   popa
+	mov si, file_buffer
-   ret
+	mov cx, [file_length]
+	call text_print_raw
+.done
+	popa
+	ret
 
 util_ls:
-   pusha
+	pusha
 
-   call disk_list_contents
+	call disk_list_contents
 
-   mov si, output_buffer
+	mov si, output_buffer
-   call os_print_string
+	call os_print_string
-   call disk_clear_output_buffer
+	call disk_clear_output_buffer
 
-   popa
+	popa
-   ret
+	ret
 
 util_basic:
 	pusha
@@ -34,6 +37,8 @@ util_basic:
 	; TODO make this more consistent to account for double spaces
 	;add si, 3 ; Move si to after 'BAS'
 	call disk_load_file
+	cmp bx, 1
+	je .done
 
 	mov si, file_buffer
 
@@ -41,5 +46,16 @@ util_basic:
 	mov si, 0
 	call basic_run_basic
 
+.done
+	popa
+	ret
+
+util_ed:
+	pusha
+	call disk_load_root
+	call disk_load_file
+	
+	call ed
+	
 	popa
 	ret

source/kernel/kernel.asm

@@ -33,13 +33,19 @@ halt:
 	%INCLUDE "source/kernel/features/sound.asm"
 	%INCLUDE "source/kernel/features/disk.asm"
 	%INCLUDE "source/kernel/features/math.asm"
+	%INCLUDE "source/kernel/features/check.asm"
 	%INCLUDE "source/kernel/features/time.asm"
 	%INCLUDE "source/kernel/features/utils.asm"
 	%INCLUDE "source/kernel/features/cli.asm"
 	%INCLUDE "source/kernel/features/misc.asm"
 	%INCLUDE "source/kernel/features/basic.asm"
+
+; PROGRAMS
+	%INCLUDE "source/kernel/programs/ed.asm"
 
 ; DATA/VARIABLES
 	%INCLUDE "source/kernel/data.asm"
+
+
 
 

source/kernel/programs/ed.asm

@@ -0,0 +1,279 @@
+; Planned commands:
+; [ ] i insert
+; [ ] a append
+; [-] d delete
+; [x] l prints lines
+; [ ] w save to disk
+; [x] q quit
+ed:
+	pusha
+	call determine_line_count
+	.main_loop:
+		; CLEAR VARIABLES
+		mov [ed_start_int], 0
+		mov [ed_end_int], 0
+		mov [ed_operation_from], 0
+		mov [ed_operation_by], 0
+
+		; Setup prompt
+		mov ax, ed_prompt
+		mov bx, 40
+		call keyboard_display_input ; AX = string location, BX = max prompt length
+		cmp bx, 1 ; I user pressed escape
+		je .quit
+		mov si, ed_prompt
+		mov bx, 0 ; Keeps track of whether comma has passed
+		jmp .get_token
+
+	.error:
+		call ed_error
+		jmp .main_loop
+
+	; Types of tokens:
+	; Number: eg 123
+	; Doller (refers to the last line) $
+	; Comma ,
+	; Command: eg i
+	; eg 123,127i
+	.get_token:
+		lodsb
+
+		; COMMA
+		cmp al, ','
+		je .comma
+
+		; DOLLAR SIGN
+		cmp al, '$'
+		je .dollar
+
+		; NUMBER
+		call check_is_number
+		jc .get_number_token
+
+		; COMMAND
+		call check_is_letter
+		jc .get_letter_token
+		jmp .error
+
+	; Assign a number to either the start or end int (start,end)
+	.dollar:
+		mov ax, [ed_line_count]
+		inc si ; Cancel out the last dec si 
+		jmp .after_int_cast
+	.get_number_token:
+		dec si
+		call string_cast_to_int ; AX = integer, DX = length of int string
+	.after_int_cast:
+		cmp bx, 0
+		je .assign_start_int
+		jg .assign_end_int
+	.assign_start_int:
+		mov [ed_start_int], ax
+		jmp .after_int_assign
+	.assign_end_int:
+		mov [ed_end_int], ax
+
+		; Check it's not after the end of the file
+		cmp ax, [ed_line_count]
+		jg .error
+		; Check it's not less than the start int
+		cmp ax, [ed_start_int]
+		jl .error 
+	.after_int_assign:
+		dec si
+		jmp .get_token
+
+
+	; Determines a command
+	.get_letter_token:
+		; If ed int
+		cmp [ed_end_int], 0
+		je .set_end_int
+	.after_end_int_check:
+		cmp al, 'l'
+		je .list
+		cmp al, 'd'
+		je .delete
+		cmp al, 'q'
+		je .quit
+		call ed_error
+		jmp .main_loop
+	; If no end int is assigned, set it to the start int
+	.set_end_int:
+		cmp bx,0
+		push ax
+		jne .end_int_to_end ; If , has been passed
+	.end_int_to_start_int:
+		mov ax, [ed_start_int]
+		mov [ed_end_int], ax
+		pop ax
+		jmp .after_end_int_check
+	.end_int_to_end:
+		mov ax, [ed_line_count]
+		mov [ed_end_int], ax
+		pop ax
+		jmp .after_end_int_check
+
+
+	; Changes the value from start int to end int
+	.comma:
+		mov bx, 1
+		jmp .get_token
+
+
+	; COMMANDS
+	;                                   DELETE                              ;
+	.delete:
+		; Adjust the ed line count
+		mov ax,[ed_end_int]
+		sub ax,[ed_start_int] ; difference in the lines
+		inc ax
+		sub [ed_line_count], ax
+
+		; set up registers to shift data left
+		; Get the byte of where the left shift will start
+		mov bx, [ed_end_int]
+		inc bx
+		call get_byte_of_line ; CX = byte of start of new line (relative to file buffer)
+		mov [ed_operation_from], cx
+
+		; Get the number of bytes to shift left by
+		mov bx, [ed_start_int]
+		call get_byte_of_line
+		mov ax, [ed_operation_from]
+		sub ax, cx
+		mov [ed_operation_by], ax
+
+		; Perform the shift
+		call shift_data_left
+
+		; Adjust the file metadata byte count
+		mov ax, [file_length]
+		sub ax, [ed_operation_by]
+		mov [file_length], ax
+
+		; Exit
+		call text_newline
+		jmp .main_loop
+
+
+	;                                   LIST                              ;
+	.list:
+		; set up registers to print the data
+		; Get the byte of where the printing will start
+		mov bx, [ed_start_int]
+		call get_byte_of_line ; CX = byte of start of new line (relative to file buffer)
+		mov si, cx
+
+		; Get the number of bytes to print
+		mov bx,[ed_end_int]
+		inc bx
+		call get_byte_of_line
+		sub cx,si
+
+		call text_newline
+		add si, file_buffer
+		call text_print_raw
+		jmp .main_loop
+
+	.quit:
+		popa
+		jmp os_start_cli
+
+; This could probably go in disk_?
+shift_data_left:
+	; Calculate source pointer
+	mov si, [ed_operation_by]
+	add si, file_buffer
+
+	; Calculate destination pointer
+	mov di, si
+	sub di, [ed_operation_by]
+
+	; Loop count
+	mov cx, file_length ; STORES THE LENGTH OF THE FILE IN BYTES
+	sub cx, ed_operation_by
+
+	; Perform the actual left shift
+	rep movsb
+
+	; Override the rest with zeroes
+	mov cx, [ed_operation_by]
+	mov al, 0
+	rep stosb
+
+	ret
+
+ed_error:
+	pusha
+
+	call text_newline
+	mov ah, 0Eh
+	mov al, '?'
+	int 10h
+	call text_newline
+
+	popa
+	ret
+
+; IN: BX = target line
+; OUT: CX = relative byte
+; TODO fix
+get_byte_of_line:
+	push dx
+	push si
+	push ax
+
+	mov si, file_buffer
+
+	xor dx,dx
+	xor cx,cx
+
+	jmp .increment_line_count
+	.line_loop:
+		xor ax,ax
+		lodsb
+		inc cx
+
+		cmp al, 0Ah
+		je .increment_line_count
+
+		jmp .line_loop
+	.increment_line_count:
+		inc dx
+		cmp dx, bx
+		jl .line_loop
+		jmp .exit
+	.exit:
+		pop ax
+		pop si
+		pop dx
+		ret
+
+determine_line_count:
+	mov si, file_buffer
+	mov dx, file_length ; STORES THE LENGTH OF THE FILE IN BYTES
+	xor cx,cx
+	.line_count_loop:
+		lodsb
+		cmp al, 0Ah
+		je .increment_line_count
+		dec dx
+		cmp dx, 0
+		jg .line_count_loop
+	mov [ed_line_count], cx
+	ret
+	.increment_line_count:
+		inc cx
+		jmp .line_count_loop
+
+ed_data_start: db "ED IS COOL"
+ed_prompt:	times 40 db 0
+ed_start_int: dw 1
+ed_end_int: dw 0
+
+ed_line_count: dw 0
+
+ed_operation_from: dw 0
+ed_operation_by: dw 0
+ed_tmp: dd 0