Character arrays - Mini Project: Build & Apply

Working with Character Arrays in C

📖 Scenario: You are creating a simple program that stores and displays a name using character arrays in C. This is like writing a name on a piece of paper and then reading it out loud.

🎯 Goal: Build a program that stores a name in a character array, counts the number of characters, and then prints the name and its length.

📋 What You'll Learn

Create a character array with a specific name

Create an integer variable to store the length of the name

Use a loop to count the characters in the array

Print the name and the length

💡 Why This Matters

🌍 Real World

Character arrays are used to store text like names, messages, or any words in many programs.

💼 Career

Understanding how to work with strings and arrays is essential for programming in C, especially in systems programming and embedded software.

1

Create a character array with the name

Create a character array called name and initialize it with the string "Alice".

C

# Create a character array called name with the value "Alice"
// Your code here

Hint

Use double quotes to create a string in C, like char name[] = "Alice";.

2

Create an integer variable for length

Create an integer variable called length and set it to 0.

C

#include 

char name[] = "Alice";

// Create an integer variable called length and set it to 0
// Your code here

Hint

Use int length = 0; to create the variable.

3

Count the characters in the array

Use a for loop with an integer variable i starting at 0 to count characters in name until you find the null character '\0'. Increase length by 1 for each character.

C

#include 

char name[] = "Alice";
int length = 0;

// Use a for loop to count characters in name until '\0'
// Your code here

Hint

Use name[i] != '\0' to check for the end of the string.

4

Print the name and its length

Use printf to print the text Name: followed by the name array, then print Length: followed by the length variable on the next line.

C

#include 

char name[] = "Alice";
int length = 0;

for (int i = 0; name[i] != '\0'; i++) {
    length++;
}

// Print the name and length
// Your code here

Hint

Use printf("Name: %s\n", name); and printf("Length: %d\n", length);.

Practice

1. What is a character array in C used for?

easy

A. To store a sequence of characters, like a word or sentence

B. To store only numbers

C. To perform mathematical calculations

D. To create a list of integers

Solution

1. Step 1: Understand character arrays

   A character array in C is a collection of characters stored in contiguous memory locations.

2. Step 2: Identify its use

   It is mainly used to store text like words or sentences, not numbers or calculations.

3. Final Answer:

   To store a sequence of characters, like a word or sentence -> Option A

4. Quick Check:

   Character array = text storage [OK]

Hint: Character arrays hold text, not numbers or math [OK]

Common Mistakes:

• Thinking character arrays store numbers only
• Confusing character arrays with integer arrays
• Assuming character arrays perform calculations

2. Which of the following is the correct way to declare a character array to hold the word "hello" in C?

easy

A. char word[6] = "hello";

B. char word[5] = {'h', 'e', 'l', 'l', 'o'};

C. char word[] = {'h', 'e', 'l', 'l', 'o', '\0'};

D. char word[5] = "hello";

Solution

1. Step 1: Understand string termination in C

   Strings in C end with a special character '\0' to mark the end.

2. Step 2: Check array size and initialization

   char word[6] = "hello"; declares an array of size 6 (5 letters + '\0') and initializes it with "hello" correctly.

3. Final Answer:

   char word[6] = "hello"; -> Option A

4. Quick Check:

   String needs space for '\0' [OK]

Hint: Remember to include space for '\0' in string arrays [OK]

Common Mistakes:

• Not allocating space for the null terminator '\0'
• Using single quotes for strings
• Declaring array size too small

3. What will be the output of the following C code?

char str[] = "cat";
printf("%c", str[3]);

medium

A. t

B. 0 (null character, no visible output)

C. c

D. Compilation error

Solution

1. Step 1: Understand string indexing

   String "cat" has characters at indices 0:'c', 1:'a', 2:'t', and index 3 is the null terminator '\0'.

2. Step 2: Print character at index 3

   Printing str[3] prints the null character which is invisible, so no visible output appears.

3. Final Answer:

   0 (null character, no visible output) -> Option B

4. Quick Check:

   str[3] = '\0' (null) [OK]

Hint: Remember strings end with '\0' at last index [OK]

Common Mistakes:

• Expecting 't' at index 3 instead of '\0'
• Thinking it causes an error
• Confusing index positions

4. Identify the error in this code snippet:

char name[5];
strcpy(name, "hello world");

medium

A. No error, code works fine

B. Incorrect use of strcpy function

C. Missing #include <string.h>

D. Array size is too small for the string

Solution

1. Step 1: Check array size vs string length

   "hello world" has 11 characters plus '\0' = 12 total, but array size is only 5.

2. Step 2: Understand consequences

   Copying this string will overflow the array, causing undefined behavior.

3. Final Answer:

   Array size is too small for the string -> Option D

4. Quick Check:

   Array must fit string + '\0' [OK]

Hint: Array size must be >= string length + 1 [OK]

Common Mistakes:

• Ignoring array size limits
• Assuming strcpy checks size
• Forgetting null terminator space

5. Given the code below, what will be the output?

char arr[10] = "abc";
arr[3] = 'd';
arr[4] = '\0';
printf("%s", arr);

hard

A. abc\0d

B. abc

C. abcd

D. Runtime error

Solution

1. Step 1: Analyze initial array content

   arr is initialized with "abc" which is 'a','b','c','\0' plus extra space.

2. Step 2: Modify characters and null terminator

   arr[3] = 'd' adds 'd' after 'c', then arr[4] = '\0' sets new string end after 'd'.

3. Step 3: Print the string

   printf prints characters until '\0', so output is "abcd".

4. Final Answer:

   abcd -> Option C

5. Quick Check:

   String ends at arr[4] '\0' [OK]

Hint: Null terminator controls string end in arrays [OK]

Common Mistakes:

• Ignoring manual null terminator placement
• Expecting original string without changes
• Confusing character and string printing