Streamline the commands and give the major parts of the code headings

src/os.asm

@@ -1,3 +1,5 @@
+;Main
+
 mov ax, 0x1000
 mov ds, ax
 
@@ -10,32 +12,28 @@ call print
 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
 
+execute:
 .hello:
-mov si, hello
+mov si, input
+mov di, command.hello
+call compare
+jnc .echo
+call hello
+jmp loop
+.echo:
+mov si, input
+mov di, command.echo
+call compare
+jnc .unknown
+call echo
+jmp loop
+.unknown:
+mov si, command.unknown
 call print
 jmp loop
 
-.echo:
+;Calls
-call read
-cmp byte [input], 0
-je loop
-mov si, input
-call print
-mov si, newline
-call print
-jmp loop
 
 print:
 lodsb
@@ -132,12 +130,39 @@ ret
 stc
 ret
 
+hello:
+mov si, .msg
+call print
+ret
+.msg:
+db "Hello world!", 0xd, 0xa, 0
+
+echo:
+call read
+cmp byte [input], 0
+je loop
+mov si, input
+call print
+mov si, newline
+call print
+ret
+
+;Data
+
 welcome:
 db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0xd, 0xa, 0
 
 prompt:
 db "> ", 0
 
+command:
+.hello:
+db "hello", 0
+.echo:
+db "echo", 0
+.unknown:
+db "Unknown command", 0xd, 0xa, 0
+
 newline:
 db 0xd, 0xa, 0
 
@@ -145,14 +170,3 @@ input:
 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