diff --git a/src/constants.asm b/src/constants.asm
index d5f70ee..e40e4d8 100644
--- a/src/constants.asm
+++ b/src/constants.asm
@@ -8,6 +8,7 @@ section .rodata
 	NR_fstat		equ	5
 	NR_lstat		equ	6
 	NR_exit			equ	60
+	NR_creat		equ	85
 	NR_umask		equ	95
 
 	; file descriptors
diff --git a/src/file.asm b/src/file.asm
index 53d0941..6242ff5 100644
--- a/src/file.asm
+++ b/src/file.asm
@@ -54,7 +54,7 @@ section .text
 
 ;----- fopen(*file[], char mode) -----;
 ; Opens a file
-; Return value: Pointer to opened file pointer, 0 (EOS) otherwise.
+; Return value: Pointer to opened file pointer, -errno otherwise
 ; Possible modes:
 ;	'r'	Read-only, file must exist
 ;	'w'	Write-only. Creates empty file or truncates an existing file
@@ -68,6 +68,82 @@ section .text
 ;	rdi	(arg) Pointer to string holding (path+)file name
 ;	rsi	Mode to open the file with (see description above)
 fopen:
+	%macro createFile 1
+	push	rdi
+	push	rsi
+	call	fexist
+	pop	rsi
+	pop	rdi
+	mov	rax, 1
+	jz	%%createFile
+	jmp	%1
+	%%createFile:
+	push	rsi
+	push	rdi
+	call	umask_get
+	pop	rdi
+	push	rdi
+	not	rax
+	mov	rsi, 00666q
+	and	rsi, rax
+	mov	rax, NR_creat
+	syscall
+	pop	rdi
+	pop	rsi
+	%endmacro
+	;;;
+	;;; ENTRY
+	;;;
+	sub	rsp, SIZE_QWORD
+
+	cmp	sil, 'r'
+	je	.setMode_r
+	cmp	sil, 'w'
+	je	.setMode_w
+	cmp	sil, 'a'
+	je	.setMode_a
+	cmp	sil, 'R'
+	je	.setMode_R
+	cmp	sil, 'W'
+	je	.setMode_W
+	cmp	sil, 'A'
+	je	.setMode_A
+	mov	rax, -EINVAL
+	jmp	.quit
+
+	.setMode_r:
+	mov	rsi, O_RDONLY
+	jmp	.open
+	.setMode_w:
+		createFile .open_w
+	.open_w:
+	mov	rsi, O_WRONLY | O_TRUNC
+	jmp	.open
+	.setMode_a:
+		createFile .open_a
+	.open_a:
+	mov	rsi, O_WRONLY | O_APPEND
+	jmp	.open
+	.setMode_R:
+	mov	rsi, O_RDWR
+	jmp	.open
+	.setMode_W:
+		createFile .open_W
+	.open_W:
+	mov	rsi, O_RDWR | O_TRUNC
+	jmp	.open
+	.setMode_A:
+		createFile .open_A
+	.open_A:
+	mov	rsi, O_RDWR | O_APPEND
+	jmp	.open
+
+	.open:
+	mov	rax, NR_open
+	syscall
+
+	.quit:
+	add	rsp, SIZE_QWORD
 	ret
 
 ;----- fclose(file) -----;
@@ -96,4 +172,15 @@ fclose:
 ;	rax*	(ret)
 ;	rdi	(arg) Pointer to string holding (path+)file name
 fexist:
+	mov	rsi, 'r'
+	call	fopen
+	test	rax, rax
+	js	.not_exist
+	mov	rdi, rax
+	call	fclose
+	mov	rax, 1
+	jmp	.quit
+	.not_exist:
+	xor	rax, rax
+	.quit:
 	ret
diff --git a/src/tests.asm b/src/tests.asm
index 98e3ca8..513cf02 100644
--- a/src/tests.asm
+++ b/src/tests.asm
@@ -123,6 +123,8 @@ section .rodata
 	TEST_atoi		equ	1
 	TEST_itoa		equ	1
 	TEST_utoa		equ	1
+	;file.asm
+	TEST_fopen		equ	1 ;Includes fclose
 
 	;;;
 	;;; Global test messages
@@ -315,13 +317,18 @@ section .rodata
 	;utoa()
 	addTestHeader(_utoa, "utoa")
 	addTest(utoa1, "// See printf outputs")
-	;fopen()
-	;fclose()
-	;fexist()
+	;fopen() / fclose() / fexist()
+	addTestHeader(_fopen, "fopen")
+	addTest(fexist1, "fexist(''testfile_1.txt'')")
+	addTest(fopen1, "fp1 = fopen(''testfile_1.txt'', 'w')")
+	addTest(fclose1, "fclose(fp1)")
+	addTest(fexist2, "fexist(''testfile_2.txt'')")
+	file1		db	"testfile_1.txt",EOS
 
 section .bss
 	strBuff1	resb	64
 	strBuff2	resb	64
+	fp1		resq	1
 
 section .text
 	global _start
@@ -1118,6 +1125,34 @@ _start:
 	printTest(utoa1)
 %endif
 
+;--- fopen() / fclose() / fexist()
+%if TEST_fopen
+	printTestHeader(_fopen)
+
+	; TEST 1
+	printTest(fexist1)
+	lea	rdi, [rel file1]
+	call	fexist
+	assert_eq(0) ;another bad test since it could exist
+
+	printTest(fopen1)
+	lea	rdi, [rel file1]
+	mov	rsi, 'w'
+	call	fopen
+	mov	[fp1], rax
+	assert_more(0)
+
+	printTest(fclose1)
+	mov	rdi, [fp1]
+	call	fclose
+	assert_eq(0)
+
+	printTest(fexist2)
+	lea	rdi, [rel file1]
+	call	fexist
+	assert_eq(1)
+%endif
+
 ;;;
 ;;; TEST RESULTS
 ;;;