Array initialization in C - Mini Project: Build & Apply

Array initialization

📖 Scenario: You are helping a small store keep track of the prices of five popular fruits. You want to store these prices in a simple list so you can use them later for calculations.

🎯 Goal: Create an array to hold the prices of five fruits, then print all the prices one by one.

📋 What You'll Learn

Create an array called prices with exactly five float values: 1.20, 0.50, 0.75, 2.00, and 1.50

Create an integer variable called i for looping

Use a for loop with i from 0 to 4 to print each price on its own line using printf

💡 Why This Matters

🌍 Real World

Arrays are used to store lists of related data like prices, scores, or measurements in many programs.

💼 Career

Understanding arrays and loops is essential for programming tasks in software development, data processing, and embedded systems.

1

Create the array of prices

Create a float array called prices with these exact values: 1.20, 0.50, 0.75, 2.00, and 1.50

C

#include 

int main() {
    // Create the float array prices with 5 values

    return 0;
}

Hint

Use the syntax: float prices[5] = {value1, value2, value3, value4, value5};

2

Add a loop counter variable

Add an integer variable called i to use as a counter for looping

C

#include 

int main() {
    float prices[5] = {1.20, 0.50, 0.75, 2.00, 1.50};
    // Declare int variable i for loop

    return 0;
}

Hint

Write int i; inside main() before the loop.

3

Use a for loop to print each price

Use a for loop with i from 0 to 4 to print each price from the prices array on its own line using printf

C

#include 

int main() {
    float prices[5] = {1.20, 0.50, 0.75, 2.00, 1.50};
    int i;
    // Add a for loop to print each price

    return 0;
}

Hint

Use for (i = 0; i < 5; i++) and inside the loop printf("%.2f\n", prices[i]);

4

Print the prices to see the output

Run the program to print all the prices stored in the prices array, each on its own line

C

#include 

int main() {
    float prices[5] = {1.20, 0.50, 0.75, 2.00, 1.50};
    int i;
    for (i = 0; i < 5; i++) {
        // Print each price
    }
    return 0;
}

Hint

Make sure your printf prints each price on its own line with two decimals.

Practice

1. Which of the following correctly declares and initializes an integer array of size 3 with values 1, 2, and 3 in C?

easy

A. int arr = {1, 2, 3};

B. int arr[3] = {1, 2, 3};

C. int arr[3] = (1, 2, 3);

D. int arr[] = 1, 2, 3;

Solution

1. Step 1: Understand array declaration syntax

   In C, arrays are declared with a type, name, and size in square brackets, e.g., int arr[3].

2. Step 2: Check initialization format

   Initialization uses curly braces with comma-separated values, e.g., {1, 2, 3}.

3. Final Answer:

   int arr[3] = {1, 2, 3}; -> Option B

4. Quick Check:

   Correct array declaration and initialization [OK]

Hint: Use curly braces {} with size in brackets [] for arrays [OK]

Common Mistakes:

• Missing square brackets for size
• Using parentheses instead of braces
• Assigning array without braces

2. Which of the following is a syntax error when initializing an array in C?

easy

A. int nums[4] = {10, 20, 30, 40};

B. int nums[5] = {0};

C. int nums[] = {5, 6, 7};

D. int nums[3] = {1, 2, 3, 4};

Solution

1. Step 1: Check array size and initializer count

   Array size is 3 but initializer has 4 values, which is invalid in C.

2. Step 2: Verify other options

   int nums[4] = {10, 20, 30, 40}; matches size and values, C infers size from initializer, B zero-initializes first element and rest are zero.

3. Final Answer:

   int nums[3] = {1, 2, 3, 4}; -> Option D

4. Quick Check:

   Initializer count > array size causes syntax error [OK]

Hint: Initializer list cannot exceed declared array size [OK]

Common Mistakes:

• Providing more initial values than array size
• Omitting size but giving initializer with extra values
• Using wrong braces

3. What is the output of the following C code?

int arr[5] = {1, 2};
printf("%d %d %d %d %d", arr[0], arr[1], arr[2], arr[3], arr[4]);

medium

A. 1 2 0 0 0

B. 1 2 garbage garbage garbage

C. 1 2 3 4 5

D. Compilation error

Solution

1. Step 1: Understand partial initialization

   When fewer values are given, remaining elements are set to zero automatically.

2. Step 2: Check printed values

   arr[0] = 1, arr[1] = 2, arr[2], arr[3], arr[4] = 0 each.

3. Final Answer:

   1 2 0 0 0 -> Option A

4. Quick Check:

   Partial init fills rest with zero [OK]

Hint: Uninitialized array elements default to zero if partially initialized [OK]

Common Mistakes:

• Assuming uninitialized elements have garbage values
• Expecting compilation error for partial init
• Confusing array size with initializer count

4. Identify the error in the following C code snippet:

int data[3];
data = {1, 2, 3};

medium

A. Missing semicolon after array declaration.

B. Array size must be omitted when initializing.

C. Arrays cannot be assigned values after declaration like this.

D. Braces should be parentheses for assignment.

Solution

1. Step 1: Understand array assignment rules

   In C, arrays cannot be assigned values after declaration using = and braces.

2. Step 2: Check other options

   Semicolon is present, size can be specified, braces are correct for initialization but not assignment.

3. Final Answer:

   Arrays cannot be assigned values after declaration like this. -> Option C

4. Quick Check:

   Array assignment after declaration is invalid [OK]

Hint: Arrays must be initialized at declaration, not assigned later [OK]

Common Mistakes:

• Trying to assign array with braces after declaration
• Confusing array assignment with pointer assignment
• Using parentheses instead of braces

5. You want to create an integer array of size 6 where the first two elements are 10 and 20, and the rest are zeros. Which of the following is the best way to initialize it in C?

hard

A. int arr[6] = {0}; arr[0] = 10; arr[1] = 20;

B. int arr[6] = {10, 20, 0, 0, 0, 0};

C. int arr[6] = {10, 20};

D. int arr[6]; arr[0] = 10; arr[1] = 20;

Solution

1. Step 1: Analyze partial initialization

   int arr[6] = {10, 20}; partially initializes first two elements; rest are zero by default, so it works.

2. Step 2: Compare with explicit zero initialization and assignment

   int arr[6] = {0}; arr[0] = 10; arr[1] = 20; explicitly zeroes all elements then assigns first two, ensuring clarity and no garbage.

3. Step 3: Evaluate best practice

   int arr[6] = {0}; arr[0] = 10; arr[1] = 20; is best for clarity and safety; int arr[6] = {10, 20}; works but less explicit; int arr[6] = {10, 20, 0, 0, 0, 0}; is verbose; int arr[6]; arr[0] = 10; arr[1] = 20; leaves uninitialized elements.

4. Final Answer:

   int arr[6] = {0}; arr[0] = 10; arr[1] = 20; -> Option A

5. Quick Check:

   Explicit zero init then assign first elements [OK]

Hint: Zero initialize first, then assign specific elements for clarity [OK]

Common Mistakes:

• Assuming partial init always safe without explicit zero
• Not initializing array before assignment
• Overwriting zeros with uninitialized values