diff --git a/headers/kprintf.h b/headers/kprintf.h
index c90ec5f..83fc8f0 100644
--- a/headers/kprintf.h
+++ b/headers/kprintf.h
@@ -13,7 +13,7 @@ enum print_level {
     KERN_DEBUG,
     KERN_DEFAULT,
     KERN_CONT
-}
+};
 
-int kprintf(enum print_level level, const char *restrict format, ...);
-int vprintf(enum print_level level, const char *restrict format, va_list ap);
\ No newline at end of file
+int kprintf(int level, const char *restrict format, ...);
+int kvprintf(int level, const char *restrict format, va_list ap);
\ No newline at end of file
diff --git a/headers/terminal.h b/headers/terminal.h
index 49c8c70..9154f16 100644
--- a/headers/terminal.h
+++ b/headers/terminal.h
@@ -1,5 +1,9 @@
 #pragma once
 
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
 enum vga_color {
 	VGA_COLOR_BLACK = 0,
 	VGA_COLOR_BLUE = 1,
@@ -22,6 +26,7 @@ enum vga_color {
 void terminal_initialize(void);
 void terminal_setcolor(uint8_t color);
 void terminal_putentryat(char c, uint8_t color, size_t x, size_t y);
-void terminal_putchar(char c);
-void terminal_write(const char* data, size_t size);
-void terminal_writestring(const char* data);
\ No newline at end of file
+int terminal_putchar(char c);
+int terminal_write(const char* data, size_t size);
+int terminal_writestring(const char* data);
+int terminal_writelong(long number);
\ No newline at end of file
diff --git a/src/kprint/kprintf.c b/src/kprint/kprintf.c
index 20a80c3..2eafaa0 100644
--- a/src/kprint/kprintf.c
+++ b/src/kprint/kprintf.c
@@ -1,4 +1,4 @@
-#include "kprint.h"
+#include "kprintf.h"
 #include "string.h"
 #include "terminal.h"
 #include "ctype.h"
@@ -11,7 +11,7 @@ int kprintf(int level, const char *restrict format, ...)
 	int		i;
 
 	va_start(va, format);
-	i = ft_vdprintf(level, format, va);
+	i = kvprintf(level, format, va);
 	va_end(va);
 
 	return (i);
diff --git a/src/kprint/kvprintf.c b/src/kprint/kvprintf.c
index 1730928..abb32fb 100644
--- a/src/kprint/kvprintf.c
+++ b/src/kprint/kvprintf.c
@@ -1,7 +1,8 @@
-#include "../../headers/kprint.h"
-#include "../../headers/string.h"
-#include "../../headers/terminal.h"
-#include "../../headers/ctype.h"
+#include "kprintf.h"
+#include "string.h"
+#include "terminal.h"
+#include "ctype.h"
+#include "stdlib.h"
 
 #include <stdarg.h>
 
@@ -30,9 +31,9 @@ int kvprintf(int level, const char *restrict format, va_list ap)
 		flag = strchr(start, '%');
 		if (flag != NULL) {
 			padding = atoll(start + 1);
-			for (; isdigit(*padding); padding++);
-			ret += print_flag(*padding, ap);
-			start = padding + 1;
+			for (; isdigit(*flag); flag++);
+			ret += print_flag(*flag, ap);
+			start = flag + 1;
 		}
 		else {
 			terminal_writestring(start);
diff --git a/src/string/strchr.c b/src/string/strchr.c
index e06e9f1..4de6e27 100644
--- a/src/string/strchr.c
+++ b/src/string/strchr.c
@@ -1,8 +1,8 @@
-
+#include <stddef.h>
 
 char *strchr(const char *str, int c)
 {
-	const char *start = str;
+	char *start = (char *) str;
 
 	while (*start)
 	{
diff --git a/src/string/strstr.c b/src/string/strstr.c
index b035d18..7353632 100644
--- a/src/string/strstr.c
+++ b/src/string/strstr.c
@@ -1,6 +1,10 @@
+#include "string.h"
+
+#include <stddef.h>
+
 char *strstr(const char *haystack, const char *needle)
 {
-	const char *start = haystack;
+	char *start = (char *) haystack;
 	size_t len;
 
 	len = strlen(needle);
diff --git a/src/terminal/terminal.c b/src/terminal/terminal.c
index bed1a42..bcfd583 100644
--- a/src/terminal/terminal.c
+++ b/src/terminal/terminal.c
@@ -1,5 +1,9 @@
 #include "../../headers/terminal.h"
 
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
 static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) 
 {
 	return fg | bg << 4;
@@ -51,7 +55,7 @@ void terminal_putentryat(char c, uint8_t color, size_t x, size_t y)
 	terminal_buffer[index] = vga_entry(c, color);
 }
 
-void terminal_putchar(char c) 
+int terminal_putchar(char c) 
 {
 	terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
 	if (++terminal_column == VGA_WIDTH) {
@@ -59,20 +63,25 @@ void terminal_putchar(char c)
 		if (++terminal_row == VGA_HEIGHT)
 			terminal_row = 0;
 	}
+    return 1;
 }
 
-void terminal_write(const char* data, size_t size) 
+int terminal_write(const char* data, size_t size) 
 {
-	for (size_t i = 0; i < size; i++)
+    size_t i;
+	for (i = 0; i < size; i++)
 		terminal_putchar(data[i]);
+    return (int) i;
 }
 
-void terminal_writestring(const char* data) 
+int terminal_writestring(const char* data) 
 {
-	terminal_write(data, strlen(data));
+    size_t len = strlen(data);
+	terminal_write(data, len);
+    return len;
 }
 
-void terminal_writelong(long number)
+int terminal_writelong(long number)
 {
     unsigned long number2 = number;