Branching templates, memory access patterns, syscall I/O, and lab-grade loop strategies 分支模板、内存访问模式、系统调用 I/O 与实验级循环策略
Log ≥5 branch templates (if/else, cascading `else if`, early exit, min/max, guard) and ≥3 loop skeletons (counted, sentinel, bidirectional). Align each with at least one past exam ID. 记录 ≥5 个分支模板（if/else、级联分支、提前返回、取 min/max、守卫）与 ≥3 个循环骨架（计数型、哨兵型、双向遍历），并与至少一个往年试题编号对齐。
Combine `slt`/`slti` with conditional branches to emulate `<`, `<=`, `>=`, while preserving fall-through blocks. Use guard labels `done`/`fail` to avoid spaghetti jumps. 通过 `slt`/`slti` 与条件跳转组合实现 `<`、`<=`、`>=`，保持落空块顺序，并用 `done`/`fail` 等守卫标签避免“面条式”跳转。
Template: compute flag → branch → handle true-case → jump to epilogue. Reuse for `max`, `min`, range checks. 模板：计算布尔标志 → 分支跳转 → 处理真分支 → 跳转到尾声。可复用于 `max`、`min`、区间判断等场景。
Anchor struct or array base in `$t0/$s0`, scale index via shifts (`sll index, index, 2`) for words, or use successive `addi` for byte walks. Remember halfword loads sign-extend. 将结构体或数组基址保存在 `$t0/$s0`，通过移位（如 `sll index, index, 2`）扩展索引实现字访存，或使用连续 `addi` 逐字节遍历。注意半字加载会符号扩展。
When swapping or comparing, stage temporaries in `$t` registers; update memory only after ensuring both loads succeeded. 交换或比较时，先在 `$t` 寄存器保存临时值，确认读取正确后再回写内存。
Counted loop: init counter → `loop:` body → `addi` → compare (`blt`, `bge`, via `slt`) → `bne` to loop. Sentinel loop: load element → check sentinel → break. 计数循环：初始化计数器 → `loop:` 循环体 → `addi` 更新 → 比较（借 `slt` 实现 `blt`、`bge`）→ `bne` 返回。哨兵循环：加载元素 → 检查哨兵值 → 满足即退出。
Two-pointer pattern (Lab03 `unordered.s`): maintain `lo`/`hi`, move indices inward until cross-over, tracking swap count. 双指针模式（Lab03 `unordered.s`）：维护 `lo`/`hi`，向内推进直至交叉，同时记录交换次数。
Store string labels in `.data`, use `la $a0, msg` + `li $v0, 4` to print, or `li $v0, 5` to read ints. Immediately move input to saved register to avoid overwriting by later syscalls. 在 `.data` 存储字符串，使用 `la $a0, msg` + `li $v0, 4` 打印，或 `li $v0, 5` 读入整数。读入后立刻将结果保存到 `$s` 寄存器，避免之后系统调用覆盖。
Wrap sequences in reusable macros (pseudo-code comments) so exam responses cite the same steps consistently. 将调用顺序封装为可复用注释模板，确保考试答题时步骤统一。
Goal: read two signed ints, print the larger. Key steps: syscall read → store → compare via `slt` → branch to label `A_is_bigger` or fall-through to `B`. Use outer label `done` for exit. 目标：读入两个有符号整数并输出较大者。关键步骤：系统调用读入 → 保存寄存器 → 通过 `slt` 比较 → 跳转到 `A_is_bigger` 或执行 `B` 分支，最后通过 `done` 标签退出。
Focus on outer count vs. inner pointer. Outer loop decrements `n-1`, inner loop compares adjacent words via offset addressing, swapping with 3 temp registers. Branch ordering: compare → no swap path first. 关注外层次数与内层指针。外循环从 `n-1` 递减，内循环通过偏移访问相邻字并使用 3 个临时寄存器交换。分支顺序：先处理无需交换的路径。
During exams, annotate invariants (“prefix [0..i) sorted”). This matches 20T3 Q7 marking notes. 考试中建议写出不变式（如“前缀 [0..i) 已排序”），与 20T3 Q7 评分说明一致。
Tutorial03 Q9 asks for reversing four bytes. Strategy: load base pointer, compute offsets 0 and 3, load bytes with `lb`, store swapped via `sb`. Extend to structure fields by adjusting stride. 教程 03 第 9 题需要反转四个字节。策略：载入基址，计算 0 与 3 的偏移，用 `lb` 读出，用 `sb` 交换回写。通过调整跨度可扩展到结构体字段。
Implement `grade_stats.s`: read `n` (≤50) scores, track max/min/average, output summary sentence in English and Chinese via two syscalls. Reuse max/min template, sentinel loop for accumulation, and maintain total in `$s1`. Include guard against `n <= 0` with early exit label. 实现 `grade_stats.s`：读入 `n` (≤50) 个分数，统计最大值/最小值/平均值，并使用两次系统调用输出中英文总结。复用取最大/最小模板，使用哨兵循环累加，总分存放 `$s1`，并在 `n <= 0` 时提前退出。
OptionalOptional: extend to median by adapting bubble-sort inner loop (counts for portfolio credit but ≤10% of study time). 可选Optional：借助冒泡排序内循环求中位数（计入学习档案但投入时间不超过 10%）。
28 basic (branches, syscalls), 8 intermediate (array loops, pointer math), 4 advanced (bubblesort trace, nested guards). Unlock with membership to start. 基础 28 题（分支、系统调用），中级 8 题（数组循环、指针运算），高级 4 题（冒泡排序、嵌套守卫）。会员解锁后即可开始。
Go to Week 3 Quiz 进入第 3 周测验Week 4 deep-dives into `.data` directives, procedure calls, and recursion-ready stack frames. Review Tutorial 04 Q11 directive list and Lab04 `lookup.s` before class. 第 4 周将深入 `.data` 伪指令、过程调用与支持递归的栈帧。课前先复习教程 04 第 11 题的伪指令清单以及 Lab04 `lookup.s`。