Add couple of commands and tweak the input length

src/os.asm

@@ -7,11 +7,27 @@ call print
 loop:
 mov si, prompt
 call print
-mov cx, 0x4d
-mov di, input
-mov al, 0
-rep stosb
-mov di, input
+call read
+cmp byte [input], 0
+je loop
+mov si, input
+mov di, cmdhello
+call compare
+jc .hello
+mov si, input
+mov di, cmdecho
+call compare
+jc .echo
+mov si, unknown
+call print
+jmp loop
+
+.hello:
+mov si, hello
+call print
+jmp loop
+
+.echo:
 call read
 cmp byte [input], 0
 je loop
@@ -32,6 +48,11 @@ jmp print
 ret
 
 read:
+mov di, input
+mov cx, 0x80
+mov al, 0
+rep stosb
+mov di, input
 mov cl, 0
 .loop:
 mov ah, 0
@@ -40,7 +61,7 @@ cmp al, 0xd
 je .return
 cmp al, 0x8
 je .backspace
-cmp cl, 0x4d
+cmp cl, 0x80
 je .loop
 cmp al, 0x20
 je .space
@@ -94,6 +115,23 @@ mov si, newline
 call print
 ret
 
+compare:
+mov al, [si]
+mov bl, [di]
+cmp al, bl
+jne .nequal
+cmp al, 0
+je .equal
+inc si
+inc di
+jmp compare
+.nequal:
+clc
+ret
+.equal:
+stc
+ret
+
 welcome:
 db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0xd, 0xa, 0
 
@@ -104,6 +142,17 @@ newline:
 db 0xd, 0xa, 0
 
 input:
-times 0x4d db 0
+times 0x80 db 0
 .end:
 db 0
+
+unknown:
+db "Unknown command", 0xd, 0xa, 0
+
+cmdhello:
+db "hello", 0
+hello:
+db "Hello world!", 0xd, 0xa, 0
+
+cmdecho:
+db "echo", 0