# Calling Convention — Output Explanation

This document explains the output of the calling convention algorithm
implemented in `calling-convention.ipynb`, tested across 3 scenarios.

---

## TEST 1: A single 1-byte argument

**Function signature:** `result = func(x)` where `x` is 8 bits (1 byte)

**Output:**
```
===== TEST 1: a 1 byte argument =====
=== State after do_function_call ===
Registers used: ['RA']
Stack: [{'type': 'caller_saved', 'reg': 'R0', 'value': 0}, {'type': 'caller_saved', 'reg': 'R1', 'value': 0}, {'type': 'caller_saved', 'reg': 'R2', 'value': 0}, {'type': 'caller_saved', 'reg': 'R3', 'value': 0}]
RS points to: 4
=== State after undo_function_call ===
Clean stack: []
RS: 0
Collected result: {'result': {'type': 'result', 'value': 42}}
```

**Explanation:**

Since there is only one argument and it fits in a single register, it is
placed directly in `RA` (the first available argument register).
Before the call, the 4 caller-saved registers (R0-R3) are pushed onto the
stack to preserve their values. `RS` points to position 4, reflecting those
4 entries. After `undo_function_call`, the stack is empty, `RS` returns to 0,
and the result value `42` is successfully collected from `RA`.