diff --git a/src/calls.inc b/src/calls.inc
new file mode 100644
index 0000000..14d4c9e
--- /dev/null
+++ b/src/calls.inc
@@ -0,0 +1,193 @@
+printstr:
+lodsb
+cmp al, 0
+je .done
+mov ah, 0xe
+int 0x10
+jmp printstr
+.done:
+ret
+
+readstr:
+mov di, readstr.out
+mov cx, 0x80
+mov al, 0
+rep stosb
+mov bl, 0
+mov ah, 0x3
+int 0x10
+mov byte [.lastln], dh
+mov di, readstr.out
+.loop:
+mov ah, 0
+int 0x16
+cmp al, 0
+je .loop
+cmp al, 0xd
+je .return
+cmp al, 0x8
+je .backspace
+cmp bl, 0x80
+je .loop
+cmp al, 0x9
+je .erase
+cmp al, 0x20
+je .space
+.char:
+mov byte [di], 0
+mov ah, 0xe
+int 0x10
+stosb
+inc bl
+jmp .checkln
+.erase:
+mov al, 0x20
+jmp .char
+.space:
+cmp byte [di], 0
+je .char
+mov al, byte [di]
+mov ah, 0xe
+int 0x10
+inc di
+inc bl
+.checkln:
+mov ah, 0x3
+int 0x10
+cmp dh, [.lastln]
+jle .loop
+mov byte [.lastln], dh
+jmp .loop
+.backspace:
+cmp bl, 0
+je .loop
+mov ah, 0x3
+int 0x10
+cmp dl, 1
+je .prevln
+mov ah, 0xe
+int 0x10
+dec di
+dec bl
+jmp .loop
+.prevln:
+mov ah, 0x2
+dec dh
+mov dl, [cpl]
+int 0x10
+dec di
+dec bl
+jmp .loop
+.return:
+mov di, readstr.end
+.findtrailing:
+dec di
+cmp byte [di], 0
+je .findtrailing
+cmp byte [di], 0x20
+je .deltrailing
+jmp .done
+.deltrailing:
+mov al, 0
+stosb
+dec di
+jmp .findtrailing
+.done:
+mov ah, 0x2
+mov dh, [.lastln]
+int 0x10
+mov si, newline
+call printstr
+ret
+.lastln:
+db 0
+.out:
+times 0x80 db 0
+.end:
+db 0
+
+cmpstr:
+mov al, [si]
+mov bl, [di]
+cmp al, bl
+jne .neq
+cmp al, 0
+je .eq
+inc si
+inc di
+jmp cmpstr
+.neq:
+clc
+ret
+.eq:
+stc
+ret
+
+byte2hexstr:
+mov di, .out
+mov si, .key
+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
+ret
+.key:
+db "0123456789abcdef"
+.out:
+times 3 db 0
+
+help:
+mov si, .out
+call printstr
+ret
+.out:
+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, "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 code of a key.", 0xd, 0xa, 0
+
+hello:
+mov si, .out
+call printstr
+ret
+.out:
+db "Hello world!", 0xd, 0xa, 0
+
+echo:
+call readstr
+cmp byte [readstr.out], 0
+je .done
+mov si, readstr.out
+call printstr
+mov si, newline
+call printstr
+.done:
+ret
+
+keycode:
+mov ah, 0
+int 0x16
+mov byte [.scan], ah
+mov byte [.ascii], al
+mov si, .prefix
+call printstr
+mov ah, [.scan]
+call byte2hexstr
+mov si, byte2hexstr.out
+call printstr
+mov ah, [.ascii]
+call byte2hexstr
+mov si, byte2hexstr.out
+call printstr
+mov si, newline
+call printstr
+ret
+.prefix:
+db "0x", 0
+.scan:
+db 0
+.ascii:
+db 0
diff --git a/src/os.asm b/src/os.asm
index 0688e9d..c42cf16 100644
--- a/src/os.asm
+++ b/src/os.asm
@@ -1,4 +1,8 @@
-;Main
+jmp start
+
+%include "calls.inc"
+
+start:
 
 mov ax, 0x1000
 mov ds, ax
@@ -8,250 +12,48 @@ int 0x10
 mov byte [cpl], ah
 
 mov si, welcome
-call print
+call printstr
 
 loop:
 mov si, prompt
-call print
-call read
-cmp byte [input], 0
+call printstr
+call readstr
+cmp byte [readstr.out], 0
 je loop
-
-execute:
+exec:
 .help:
-mov si, input
-mov di, command.help
-call compare
+mov si, readstr.out
+mov di, cmd.help
+call cmpstr
 jnc .hello
 call help
 jmp loop
 .hello:
-mov si, input
-mov di, command.hello
-call compare
+mov si, readstr.out
+mov di, cmd.hello
+call cmpstr
 jnc .echo
 call hello
 jmp loop
 .echo:
-mov si, input
-mov di, command.echo
-call compare
+mov si, readstr.out
+mov di, cmd.echo
+call cmpstr
 jnc .keycode
 call echo
 jmp loop
 .keycode:
-mov si, input
-mov di, command.keycode
-call compare
-jnc .unknown
+mov si, readstr.out
+mov di, cmd.keycode
+call cmpstr
+jnc .error
 call keycode
 jmp loop
-.unknown:
-mov si, command.unknown
-call print
+.error:
+mov si, cmd.error
+call printstr
 jmp loop
 
-;Calls
-
-print:
-lodsb
-cmp al, 0
-je .done
-mov ah, 0xe
-int 0x10
-jmp print
-.done:
-ret
-
-clear:
-mov di, input
-mov cx, 0x80
-mov al, 0
-rep stosb
-ret
-
-read:
-call clear
-mov bl, 0
-mov ah, 0x3
-int 0x10
-mov byte [.lastline], dh
-mov di, input
-.loop:
-mov ah, 0
-int 0x16
-cmp al, 0
-je .loop
-cmp al, 0xd
-je .return
-cmp al, 0x8
-je .backspace
-cmp bl, 0x80
-je .loop
-cmp al, 0x9
-je .erase
-cmp al, 0x20
-je .space
-.character:
-mov byte [di], 0
-mov ah, 0xe
-int 0x10
-stosb
-inc bl
-jmp .linecheck
-.erase:
-mov al, 0x20
-jmp .character
-.space:
-cmp byte [di], 0
-je .character
-mov al, byte [di]
-mov ah, 0xe
-int 0x10
-inc di
-inc bl
-.linecheck:
-mov ah, 0x3
-int 0x10
-cmp dh, [.lastline]
-jle .loop
-mov byte [.lastline], dh
-jmp .loop
-.backspace:
-cmp bl, 0
-je .loop
-mov ah, 0x3
-int 0x10
-cmp dl, 1
-je .prevline
-mov ah, 0xe
-int 0x10
-dec di
-dec bl
-jmp .loop
-.prevline:
-mov ah, 0x2
-dec dh
-mov dl, [cpl]
-int 0x10
-dec di
-dec bl
-jmp .loop
-.return:
-mov di, input.end
-.findtrailingspace:
-dec di
-cmp byte [di], 0
-je .findtrailingspace
-cmp byte [di], 0x20
-je .erasetrailingspace
-jmp .done
-.erasetrailingspace:
-mov al, 0
-stosb
-dec di
-jmp .findtrailingspace
-.done:
-mov ah, 0x2
-mov dh, [.lastline]
-int 0x10
-mov si, newline
-call print
-ret
-.lastline:
-db 0
-
-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
-
-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
-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 code of a key.", 0xd, 0xa, 0
-
-hello:
-mov si, .msg
-call print
-ret
-.msg:
-db "Hello world!", 0xd, 0xa, 0
-
-echo:
-call read
-cmp byte [input], 0
-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
-
 cpl:
 db 0
 
@@ -261,7 +63,7 @@ db 0xd, 0xa, "Welcome to EttinOS!", 0xd, 0xa, 0xd, 0xa, 0
 prompt:
 db "> ", 0
 
-command:
+cmd:
 .help:
 db "help", 0
 .hello:
@@ -270,13 +72,8 @@ db "hello", 0
 db "echo", 0
 .keycode:
 db "keycode", 0
-.unknown:
+.error:
 db "Unknown command", 0xd, 0xa, 0
 
 newline:
 db 0xd, 0xa, 0
-
-input:
-times 0x80 db 0
-.end:
-db 0