Bytecode question: Added clarification of arithemtic behaviour: modulo on 10^9 + 7

Author: TianLangHin

competition/bytecode/prob.md

@@ -54,17 +54,21 @@ Next, here is a list of all types of bytecode instructions it supports.
   associated with the same `<name>`.
   Such a `LABEL` line is guaranteed to exist such that any `JUMP` is valid,
   and that exactly *one* line will match, making this instruction always unambiguous.
-* `ADD <value> <value>`: Add the two `<value>`s and push the result on the top of the **stack**.
-* `SUB <value> <value>`: Subtract the second `<value>` from the first `<value>`
+* `ADD <value> <value>`: Add the two `<value>`s, take its modulo of `10^9 + 7`,
   and push the result on the top of the **stack**.
-* `MUL <value> <value>`: Multiply the two `<value>`s together
+* `SUB <value> <value>`: Subtract the second `<value>` from the first `<value>`,
+  take its modulo of `10^9 + 7`,
+  and push the result on the top of the **stack**.
+* `MUL <value> <value>`: Multiply the two `<value>`s together,
+  take its modulo of `10^9 + 7`,
   and push the result on the top of the **stack**.
 * `DIVMOD <value> <value>`: Conduct a division of the first `<value>` by the second `<value>`.
   First push the quotient of the division onto the **stack**,
   then push the remainder (modulo) of the division onto the **stack**.
   If, however, the second `<value>` is zero, then instead of the quotient and remainder,
   push the original `<value>`s onto the **stack** instead.
   (i.e., push the first `<value>` first, then the second `<value>` next.)
+  In both cases, both values being pushed onto the **stack** are modulo'd by `10^9 + 7`.
 * `CMP <value> <value>`: Compares the first `<value>` against the second `<value>`.
   If the two are equal, push `0` onto the **stack**.
   If the first is greater than the second, push `1` onto the **stack**.
@@ -113,7 +117,7 @@ The following instructions will be executed:
 5. `LOAD 2`: Loads the value `2` onto the stack.
 6. `STORE !`: Pops `2` from the stack, stores it in the output register.
 7. `ADD a !`: Adds the values of the variable `a` and the output register,
-  which is `6 + 2 = 8`. Hence, `8` is loaded onto the stack.
+  which is `6 + 2 = 8`. Hence, `8 % (10^9 + 7) = 8` is loaded onto the stack.
 8. `STORE b`: Pops `8` from the stack, stores it in the variable `b`.
 9. `BRANCHCMP b 8 EQ pqr`: Compares the variable `b` with the value `8`.
   Since they are equal in value, jump to the line that reads `LABEL pqr` (second from top).