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STUDENT NOTES · C & C++ WEEK 3 OF 8
Arrays & the Missing Seatbelts 📦
C's train of boxes — faster than Python's lists, but with NO safety rails. Time to learn careful driving.
1Arrays — fixed-size trains
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Chip: Declared with a size, indexed from 0 — and that size NEVER changes. No .append() in C; you ask for exactly the wagons you need, up front.
2Looping an array
3⚠️ The famous missing seatbelt
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Bugly: 3 wagons. Ask for wagon 3 (the 4th!). Python throws IndexError. C… hehehe… C just READS WHATEVER MEMORY IS THERE:
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Professor Hoot: Undefined behavior — maybe garbage, maybe a crash, maybe it "works" today and explodes at the demo. C trusts you completely. Be trustworthy.
4Strings — char arrays with a secret ending
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Chip: A C string is a char array ending in an invisible \0 (the null terminator). That's how printf knows where to stop reading. strlen counts everything BEFORE it.
5Quick quiz! 🧠
int a[3] = {10, 20, 30}; — what does a[3] give in C?
💡 C has no bounds checking. It reads whatever bytes sit past the array. The scariest — and most educational — bug in C.
char team[10] can safely hold a name of at most…
💡 One slot always belongs to the invisible \0. Overfill it and you've invented a buffer overflow.
6Your mission 🚀
Mission 1: Make an int array of 5 marks and print the total with a loop.
Mission 2: Store your name in a char array and print it with %s, then its length with strlen.
Mission 3: Read a[5] on a 3-element array ON PURPOSE (in onlinegdb). Observe the garbage. Feel the danger. Never do it again. 😅
Week 3 complete — you drive without seatbelts now. Carefully. 📦
Next: POINTERS. The chapter that makes C famous — and finally makes it click.
Go to Week 4: Pointers →