adds example for calling external C func from masm

src/1_4.asm

@@ -10,4 +10,6 @@ main proc           ; the main procedure
     call asm_proc   ; call our proc
     ret
 main endp
-    end
+    end
+
+

src/1_5.asm

@@ -0,0 +1,21 @@
+    option casemap:none
+
+    .data
+
+fmt_str byte 'Hello World!', 10, 0 ; here 10 is the newline feed
+
+    .code
+
+    externdef printf:proc
+
+    public asm_func
+
+asm_func proc
+    sub rsp, 56
+    lea rcx, fmt_str ; load the format string into the RCX register to be used by the printf
+    call printf
+    add rsp, 56
+    ret
+asm_func endp
+    
+    end