Add byte2hex call and help and keycode commands

src/os.asm

@@ -14,6 +14,13 @@ cmp byte [input], 0
 je loop
 
 execute:
+.help:
+mov si, input
+mov di, command.help
+call compare
+jnc .hello
+call help
+jmp loop
 .hello:
 mov si, input
 mov di, command.hello
@@ -25,9 +32,16 @@ jmp loop
 mov si, input
 mov di, command.echo
 call compare
-jnc .unknown
+jnc .keycode
 call echo
 jmp loop
+.keycode:
+mov si, input
+mov di, command.keycode
+call compare
+jnc .unknown
+call keycode
+jmp loop
 .unknown:
 mov si, command.unknown
 call print
@@ -45,11 +59,15 @@ jmp print
 .done:
 ret
 
-read:
+clear:
 mov di, input
 mov cx, 0x80
 mov al, 0
 rep stosb
+ret
+
+read:
+call clear
 mov di, input
 mov cl, 0
 .loop:
@@ -130,6 +148,36 @@ ret
 stc
 ret
 
+byte2hex:
+call clear
+mov di, input
+mov si, .hex
+mov cx, 0x2
+.loop:
+rol ax, 0x4
+mov bx, ax
+and bx, 0xf
+mov bl, [si + bx]
+mov [di], bl
+inc di
+dec cx
+jnz .loop
+; mov si, input
+ret
+.hex:
+db "0123456789abcdef"
+
+help:
+mov si, .input
+call print
+mov si, .commands
+call print
+ret
+.input:
+db "Input:", 0xd, 0xa, "* Typing a character overwrites the cursor location.", 0xd, 0xa, "* The tab key erases the cursor location.", 0xd, 0xa, "* The space and backspace keys move the cursor.", 0xd, 0xa, 0
+.commands:
+db "Commands:", 0xd, 0xa, "* help: you are reading it.", 0xd, 0xa, "* hello: a hello world program.", 0xd, 0xa, "* echo: echoes its input.", 0xd, 0xa, "* keycode: echoes the BIOS scancode of a key.", 0xd, 0xa, 0
+
 hello:
 mov si, .msg
 call print
@@ -140,12 +188,38 @@ db "Hello world!", 0xd, 0xa, 0
 echo:
 call read
 cmp byte [input], 0
-je loop
+je .done
+mov si, input
+call print
+mov si, newline
+call print
+.done:
+ret
+
+keycode:
+mov ah, 0
+int 0x16
+mov byte [.scan], ah
+mov byte [.ascii], al
+mov si, .prefix
+call print
+mov ah, [.scan]
+call byte2hex
+mov si, input
+call print
+mov ah, [.ascii]
+call byte2hex
 mov si, input
 call print
 mov si, newline
 call print
 ret
+.prefix:
+db "0x", 0
+.scan:
+db 0
+.ascii:
+db 0
 
 ;Data
 
@@ -156,10 +230,14 @@ prompt:
 db "> ", 0
 
 command:
+.help:
+db "help", 0
 .hello:
 db "hello", 0
 .echo:
 db "echo", 0
+.keycode:
+db "keycode", 0
 .unknown:
 db "Unknown command", 0xd, 0xa, 0