Add Explicit Return Types and Discussion on Return Value

Problem/Motivation

The current codebase lacks explicit return types in functions, leading to potential ambiguity and maintenance issues. Additionally, there is a need for discussion regarding whether the getBalance() function should return NULL or 0 when there is no balance.

Fix

Implement return types for all functions across the codebase.

Steps to reproduce

Review functions throughout the codebase for missing return types.

Proposed resolution

Audit the codebase to identify functions without return types.
Add explicit return types to all identified functions.
Discuss whether getBalance() should return NULL or 0.
MR Link