add README for exmaples

examples/README.md

@@ -0,0 +1,7 @@
+## Assemble
+
+    ../assembler/fvm-as fibo.asm fibo.bin
+
+## Run
+
+    ./fvm fibo.bin

examples/fibo.asm

@@ -1,13 +1,20 @@
-    imm 40
+    ;; fibo(30)
+    imm 30
     fibo rel call
+    ;; pop arguments and push return value to stack
     pop rv
+    ;; call print_number (syscall number is 1)
     imm 1 syscall
     exit
 fibo:
+    ;; setup stack pointer and base pointer
     bp sp sbp
+    ;; get first argument
     imm 2 bpick
+    ;; if (x > 2) then
     imm 2 gt
     .else rel jz
+    ;; return fibo(x - 2) + fibo(x - 1)
     imm 2 bpick
     imm 1 sub
     fibo rel call
@@ -19,6 +26,7 @@ fibo:
     srv
     .end rel jmp
 .else:
+    ;; else return 1
     imm 1 srv
     .end rel jmp
 .end: