Module 1: C Programming Fundamentals: Mistake Clinic

This clinic turns wrong moves into reusable judgment. Use it after each practice page and again before the quiz or checkpoint.

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Module-Specific Mistake Radar

Start with these traps. Replace or extend them with real mistakes from your own work.

Mistake to look for	Where it shows up	Symptom	Repair evidence
Finishing C Compilation and Mental Model Lab with only a final answer	C Compilation and Mental Model Lab	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Types, Control Flow, and Functions Workshop with only a final answer	Types, Control Flow, and Functions Workshop	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Arrays, Strings, and I/O Clinic with only a final answer	Arrays, Strings, and I/O Clinic	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Code Katas with only a final answer	Code Katas	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Treating C Is a Portable Assembler as vocabulary instead of a tool	C Is a Portable Assembler	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.
Treating The Translation Pipeline as vocabulary instead of a tool	The Translation Pipeline	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.

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Practice Mistake Checks

Pull any miss from these checks into your mistake log.

C Compilation and Mental Model Lab

Source: practice/01-c-compilation-and-mental-model-lab.md

For each statement, identify the error:

1. "The preprocessor imports headers like Python imports modules."
2. "If the program runs fine in debug mode, there is no undefined behavior."
3. "The compiler reports every undefined reference it detects."
4. "gcc -std=c89 means the compiler targets only 32-bit processors."
5. "A translation unit is the same thing as an executable."

Types, Control Flow, and Functions Workshop

Source: practice/02-types-control-flow-and-functions-workshop.md

For each, identify the error:

1. if (x = 5) { ... }
2. #define SQUARE(x) x*x
3. printf("%d\n", sizeof(int));
4. int arr[10]; void f(int arr[10]) { size_t n = sizeof arr / sizeof arr[0]; ... }
5. register int *p = &x;
6. for (unsigned i = n; i >= 0; i--) { ... }
7. int *arr = (int*)malloc(sizeof(int)); for (i = 0; i < 10; i++) arr[i] = i;
8. #define MAX 100; used as for (int i = 0; i < MAX; i++)

Arrays, Strings, and I/O Clinic

Source: practice/03-arrays-strings-and-io-clinic.md

For each, identify the error:

1. char name[8]; strcpy(name, "Kernighan");
2. char *s = "hi"; s[0] = 'H';
3. char buf[100]; sprintf(buf, "%s %s", a, b); where a and b are user input
4. char buf[100]; fgets(buf, 100, stdin); buf[strlen(buf)-1] = '\0';
5. int n; scanf("%d", n);
6. printf(user_input);
7. char dst[5]; strncpy(dst, "hello world", 5); then puts(dst);
8. void f(int a[10]) { size_t n = sizeof a / sizeof a[0]; /* loop over n */ }

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Repair Protocol

For each real mistake:

1. Reproduce the failure on the smallest example, trace, proof, query, command, or design sketch.
2. Name the hidden assumption.
3. Repair the artifact.
4. Save evidence that changed: failing then passing test, corrected proof step, revised diagram, safer command, benchmark, or review note.
5. Add one retrieval card beginning with Check... before... or Do not use... when....

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Mistake Log

Date	Mistake	Symptom	Root cause	Repair evidence	Retrieval card
Starter	Pick one radar row above	Explain how it would fail in this module	Name the assumption	Add a counterexample or corrected artifact	Write the card before closing the page

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Completion Standard

• At least five real mistakes are logged.
• At least two mistakes include a counterexample or failing test.
• At least one mistake connects to an older semester skill.
• At least one correction changes code, a proof, a diagram, a command transcript, a query, or a design decision.