diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 0d108fe..357ce1b 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -2,7 +2,7 @@ name: Build OpenDOS
 
 on:
   push:
-    branches: [main]
+    branches: ['**']
   pull_request:
     branches: [main]
 
diff --git a/build.sh b/build.sh
index e507071..aa1aad2 100755
--- a/build.sh
+++ b/build.sh
@@ -9,7 +9,7 @@ MOUNT_POINT="img"
 GRUB_CFG="grub.cfg"
 
 ASM_FILES=("kernel.asm")  
-C_FILES=("kernel.c" "string.c" "io.c" "ata.c" "keyboard.c" "fat12.c" "fs.c" "speaker.c")    
+C_FILES=("kernel.c" "string.c" "io.c" "ata.c" "keyboard.c" "fat12.c" "fs.c" "speaker.c" "syscall.c")    
 
 RED='\033[31m'
 GREEN='\033[32m'
diff --git a/src/include/syscalls.h b/src/include/syscalls.h
new file mode 100644
index 0000000..06462a6
--- /dev/null
+++ b/src/include/syscalls.h
@@ -0,0 +1,21 @@
+#define SYS_INPUT  0
+#define SYS_PRINT  1
+#define SYS_PRINTERR  2
+#define SYS_EXIT   5
+
+/*
+// future use:
+static inline uint32_t syscall(uint32_t number, uint32_t arg1, uint32_t arg2) {
+    uint32_t ret;
+    asm volatile (
+        "int $0x80" 
+        : "=a"(ret)
+        : "a"(number), "b"(arg1), "c"(arg2)
+    );
+    return ret;
+}
+
+void hello() {
+    syscall(SYS_PRINT, (uint32_t)"Hello from user space!\n", 0);
+}
+*/
diff --git a/src/syscall.c b/src/syscall.c
new file mode 100644
index 0000000..f327846
--- /dev/null
+++ b/src/syscall.c
@@ -0,0 +1,26 @@
+#include "os.h"
+#include "syscalls.h"
+
+uint32_t handle_syscall(uint32_t number, uint32_t arg1) {
+    switch (number) {
+        case SYS_INPUT:
+            // TODO: return text from input
+            break;
+
+        case SYS_PRINT:
+            k_printf("%s", (char*)arg1);
+            break;
+
+        case SYS_PRINTERR:
+            k_printf("\x1b[31m%s\x1b[0m\n", (char*)arg1);
+            break;
+
+        case SYS_EXIT:
+            // TODO: exit from program
+            break;
+
+        default:
+            return -1; // unknown syscall
+    }
+    return 0;
+}