Overview
Welcome to Week 6 of C programming! This week, we’ll explore arrays, randomness, and special control flow keywords. By the end of this tutorial, you will:
- Understand how to declare and use 1D and 2D arrays
- Generate and use random numbers using
rand() - Use
break, continue, and goto for controlling loops - Understand how to use variable-length arrays (VLAs)
- Print and understand memory addresses using
%p
Time Breakdown
- Control Flow (
break, continue, goto) - 1D Arrays and Address Printing
- Random Number Generation with
rand() - 2D Arrays and Variable-Length Arrays
- Exercises & Q/A
1.Control Flow Keywords: break, continue, goto
Control flow keywords help change the normal execution of loops.
Example 1: Skip 0s and stop at 999
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| #include <stdio.h>
int main(void) {
int num;
while (1) {
scanf("%d", &num);
if (num == 0) continue;
if (num == 999) break;
printf("You entered: %d\n", num);
}
return 0;
}
|
Example Output:
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| 1
You entered: 1
2
You entered: 2
3
You entered: 3
0
2
You entered: 2
3
You entered: 3
4
You entered: 4
999
|
2. 1D Arrays & Address Printing
Arrays store a collection of variables. Using %p allows you to see memory addresses.
Example 2: Print array values and addresses
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| #include <stdio.h>
int main(void) {
int arr[3] = {1, 2, 3};
for (int i = 0; i < 3; i++) {
printf("arr[%d] = %d, address = %p\n", i, arr[i], &arr[i]);
}
return 0;
}
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Example Output:
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| arr[0] = 1, address = 0x16b3e0564
arr[1] = 2, address = 0x16b3e0568
arr[2] = 3, address = 0x16b3e056c
|
3. Random Number Generation
rand() generates pseudorandom integers. Use srand(time(0)) to ensure different results on each run.
Example 3: Generate 10 random numbers
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| #include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(void) {
srand(time(0));
for (int i = 0; i < 10; i++) {
printf("%d \n", rand() % 10); // random number from 0 to 9
}
return 0;
}
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Example Output:
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| 0
9
1
0
3
8
1
2
4
|
4. 2D Arrays and Variable-Length Arrays
You can create 2D arrays with fixed or variable dimensions using int M[r][c].
Example 4: Generate 10 random numbers
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| #include <stdio.h>
int main(void) {
int r = 2, c = 3;
int M[r][c];
printf("Enter 6 integers:\n");
for (int i = 0; i < r; i++)
for (int j = 0; j < c; j++)
scanf("%d", &M[i][j]);
printf("Matrix:\n");
for (int i = 0; i < r; i++) {
for (int j = 0; j < c; j++)
printf("%d ", M[i][j]);
printf("\n");
}
return 0;
}
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Example Output:
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| 1 2 3 4 5 6
Matrix:
1 2 3
4 5 6
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Exercise 1: Count how many even numbers are in an array.
- Ask the user to enter 10 integers into a 1D array.
- Print how many of them are even.
Example Output:
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| Number of even values: 4
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Exercise 2: Calculate the sum of a 2D array.
- Ask the user to input a 3x3 matrix
- Print the total sum of all elements.
Example Output:
Exercise 3: CFill an array with random numbers and find the maximum.
- Use
rand() to generate 10 random numbers - Print the largest number
Example Output:
Exercise 4: Work with Variable-Length Arrays.
- Ask the user how many elements they want to enter
- Create a VLA and store those values
- Print them in entered order
Example Output:
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| 5
1 2 3 4 5
1 2 3 4 5
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Bonus Challenge: Matrix Diagonal Sum
Ask the user to input a 3x3 matrix and print the sum of the diagonal elements.
Summary & Wrap-Up
This week, we covered:
- Using
break, continue, and goto to control loops - How arrays and pointers relate
- Using
rand() and variable-length arrays
Next Week: Midterm!
Happy coding! 🚀