1	CS 211: Introduction to Computer Programming II Instructor: Brian M. Dennis Teaching Assistants: Tom Lechner, Bin Lin http://www.cs.northwestern.edu/~bmd/cs211/
2	Pass by value void swap(int x, int y) { int old_x = x; x = y; y = old_x; } int main() { int x = 10, y = 20; swap(x, y); cout << "x: " << x; cout << " y: " << y; cout << "\n"; return 1; }
3	Pass by reference void swap(int& x, int &y) { int old_x = x; x = y; y = old_x; } int main() { int x = 10, y = 20; swap(x, y); cout << "x: " << x; cout << " y: " << y; cout << "\n"; return 1; }
4	Pass by value reference int* swap(int* x_ptr, int y_ptr) { int z_ptr, z; int old_x = x_ptr; x_ptr = y_ptr; *y_ptr = old_x; return y_ptr; } int main() { int x = 10, y = 20; swap(&x, &y); cout << "x: " << x; cout << " y: " << y; cout << "\n"; return 1; }
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6	Memory Array of bytes Byte == 8 bits Often written in Hex, base 16 Every variable Some storage in memory A type A size ints = 4 bytes floats = 4 bytes doubles = 8 bytes char = 1 byte pointer (of any type) = 4 bytes
7	Increment shorthands int main() { int x = 100; int z = 3; x = x + 1; // The following only work on lvalues x += 1; // Add 1 to x x += z, x += z * z; // Add 3, then add 9 x++; // Increment x, ret oldx ++x; // Increment x, ret newx }
8	for statement int fib_pure_iter(int n) { int a = 1; int b = 0; int old_a = 1; for (int i = 0; i < n; i += 1) { old_a = a; a = a + b; b = old_a; } return b; }
9	for statement int fib_pure_iter(int n) { int a = 1; int b = 0; int old_a = 1; for (int i = 0; i < n; i++) { old_a = a; a = a + b; b = old_a; } return b; }
10	Decrement shorthands int main() { int x = 100; int z = 4; x = x - 1; // The following only work on lvalues x -= 1; // Subtract 1 from x x -= z, x -= z * z; // Sub 4, then sub 16 x--; // Decrement x, ret oldx --x; // Decrement x, ret newx }
11	while statement int fib_pure_iter(int n) { int a = 1; int b = 0; int old_a = 1; while (0 < n--) { old_a = a; a = a + b; b = old_a; } return b; }
12	Arrays // Arrays: homogeneous, sequential, // indexed, contiguous storage, zero based int main() { int int_array[10]; // Array of 10 integers // 40 bytes of storage double double_array[5]; // Array of 5 doubles // 20 bytes of storage char char_array[10]; // Array of 10 chars // 10 bytes of storage }
13	Arrays: access #include <iostream> using namespace std; int fib(int n); int main() { int fib_vals[10]; for(int i = 0; i < 10; i++) { fib_vals[i] = fib(i); } int j = 10; while(j--) { cout << "Fib: " << j << " = " << fib_vals[j] << "\n"; } }
14	Arrays: access #include <iostream> using namespace std; int main() { char hw = "Hello, World"; for (int j = 0; hw[j]; j++) { cout << hw[j]; } cout << "\n"; for (int k = 12; 0 <= k; k--) { cout << hw[k]; } cut << "\n"; }
15	Help us help you Bring the source code Trim to smallest broken example What are you trying to get done? How is your code supposed to be doing it? How did you run your code? What did you expect? What did you get?
16	That’s a Wrap Takeaway Pointer basics Array basics Reading 4.1 – 4.4 5.1 – 5.4