Learning C++ from Scratch: Practical Cases of if-else Conditional Statements

This article introduces the if-else conditional statement in C++, which is used to execute different operations based on conditions. The core idea is that if the condition is true, the corresponding code block is executed; otherwise, another block is executed, endowing the program with decision-making capabilities. There are three syntax forms: 1. Single condition: Use `if(condition)` to execute the corresponding code block. 2. Binary choice: Use `if-else`, where the if block runs if the condition is true, and the else block runs otherwise. 3. Multi-condition: Use `else if`, with conditions judged from top to bottom in descending order of scope (e.g., for grading, first check ≥90, then 80-89, etc.) to avoid logical errors. Practical cases include: - Determining odd/even numbers (using `%2 == 0`). - Grading scores (outputting A/B/C/D/F for 0-100, with handling for invalid scores). Key notes: - The condition expression must be a boolean value (e.g., use `==` instead of assignment `=`). - `else if` order must be from large to small ranges. - Braces are recommended for code blocks. - Avoid incorrect condition ranges. Summary: if-else is a fundamental control statement. Mastering its syntax and logical order allows handling more branches through nesting or switching, cultivating program decision-making thinking.