diff --git a/src/constants.asm b/src/constants.asm
index b0a1a47..fd30701 100644
--- a/src/constants.asm
+++ b/src/constants.asm
@@ -1 +1,23 @@
 section .rodata
+	; syscall
+	NR_read			equ	0
+	NR_write		equ	1
+	NR_exit			equ	60
+
+	; file descriptors
+	FD_stdin		equ	0
+	FD_stdout		equ	1
+	FD_stderr		equ	2
+
+	; ASCII
+	EOS			equ	0
+	TAB			equ	9
+	NL			equ	10
+	DQUO			equ	34
+
+	; Sizes
+	RBP_OFFSET_CALLER	equ	16
+	SIZE_QWORD		equ	8
+	SIZE_DWORD		equ	4
+	SIZE_WORD		equ	2
+	SIZE_BYTE		equ	1
diff --git a/src/core.asm b/src/core.asm
index 2e069bf..a19062f 100644
--- a/src/core.asm
+++ b/src/core.asm
@@ -1 +1,9 @@
 %include "src/constants.asm"
+
+section .text
+	global	exit
+
+;----- exit(exit_code) -----;
+exit:
+	mov	rax, NR_exit
+	syscall
diff --git a/src/tests.asm b/src/tests.asm
index 2e069bf..b9715c4 100644
--- a/src/tests.asm
+++ b/src/tests.asm
@@ -1 +1,18 @@
 %include "src/constants.asm"
+
+; core.asm
+extern	exit
+; console.asm
+; string.asm
+; convert.asm
+
+section .text
+	global _start
+_start:
+	push	rbp
+	mov	rbp, rsp
+	sub	rsp, SIZE_QWORD
+
+	leave
+	mov	rdi, 0
+	call	exit