KwickClips C

C: 35 short revision clips

One idea per clip, with the answer written out underneath. Each clip links back to the full C lesson it came from.

Table: OS Linux, devices washer chip, compilers Python, all using C.

Why is C still used?42 sec $C code: #include <stdio.h>, int main() with printf("Hi\n") and return 0, output Hi.$ Where does a C program start running?41 sec

Table of steps and files: edit hello.c, compile hello.o, link hello.exe, run output.

Which file does compiling make?44 sec

Terminal: gcc hello.c -o hello, then ./hello prints Hello.

What does gcc do?43 sec

Table: marks2 yes, 2marks no (digit), roll no no (space), int no (keyword).

Is roll no a valid name?43 sec

Table of C types and sizes: char 1, int 4 (old: 2), float 4, double 8.

Why do some books say int is 2 bytes?44 sec

C code with #define PASS 33, int r = 45 and printf of r - PASS giving 12.

What must come before using a variable in C?41 sec

C code const int SEATS = 72; then SEATS = 80; with a read-only error comment.

What happens if you assign to a const?40 sec $C printf("%d %c %.1f\n", 12, 'B', 87.5) printing 12 B 87.5.$ What does %.1f print for 87.5?46 sec

What is & called?39 sec

C code char ch; ch = getchar(); putchar(ch);

Does getchar need a format specifier?41 sec $Wrong vs right table: scanf with x vs &x, %d vs %f for 2.5, "Hi" vs "Hi\n".$ What does printf("%d", 2.5) print?43 sec

Table: arithmetic 17 % 5 is 2, relational 10 > 7 is 1, logical a && b, assignment x += 5.

What does % give?43 sec

C code int a = 5; b = a++; c = ++a; printing 5 7.

Are a++ and ++a the same?43 sec

C code printing n > 5 ? 1:0 and n & 3 with output 1 2.

What does 6 & 3 give?42 sec

C code printing 2 + 3 * 4 and 20 - 5 - 3 with output 14 12.

Why is 20 - 5 - 3 equal to 12?43 sec

C code int m = 20; if (m >= 33) printf Pass else printf Fail, output Fail.

What prints for m = 20?44 sec

C code else if ladder with m = 75 printing A.

What prints for 75?40 sec

C switch(2) with case 2 and case 3 and no break, output Two Three.

What does break do in a switch?43 sec

Slide: goto top; jumps to top:, flow becomes hard to follow, makes spaghetti code.

What does goto do?38 sec

Table: while checks before, runs 0; for checks before, runs 0; do-while checks after, runs 1.

Which loops are entry controlled?41 sec

C nested for loops printing *, **, *** on three lines.

Which loop handles columns?41 sec

C for loop with continue at 3 and break at 5, printing 1 2 4.

What does continue do?39 sec

C code int f = 1; for loop f = f * i to 5, output 120.

What is 5! ?42 sec

C code int add(int a, int b) returning a + b, called from main with 4 and 5, output 9.

What are the four parts of a definition?41 sec

Slide: int add(int, int); goes before main and ends with a semicolon, no body.

Does a prototype have a body?42 sec

Table: swap(x, y) copies gives 5, 9; swap(&x, &y) addresses gives 9, 5.

Which call changes x and y?43 sec

C function big returning a if a > b else b, called with 8 and 3, output 8.

How many values can return send?37 sec

C code global int n = 1, local int n = 2 in main, output 2.

Where does a local variable live?41 sec

Table: local lives block start to end, static and global live program start to end.

What is lifetime?40 sec

Table of auto, register, static and extern with default value and lifetime.

Which storage classes start at zero?44 sec

List: temporary work auto, remember between calls static, share across files extern.

What is the default storage class?41 sec

Slide: base case stops the calls, each call gets a stack frame, no base case means stack overflow.

What should you write first?42 sec

C recursive factorial f(n) with output 120.

What does f(5) return?43 sec

Table comparing recursion and loop on memory, speed and stopping point.

Which is usually faster?41 sec

Full C lessons All KwickClips

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C: 35 short revision clips

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