🔤 Strings in C Programming
Character Arrays, String Functions & Practical Examples
Learn How C Programs Store and Manipulate Text 🚀
🚀 Introduction
In the previous lesson, we learned about arrays. An array can store multiple values of the same data type.
But what if we want to store text such as:
- Your name
- Your city
- A sentence
- A password
- A message
In C programming, text is generally stored using a character array, which we commonly call a string.
💡 Simple Definition
A string in C is a sequence of characters terminated by a special null character '\0'.
🔤 String as a Character Array
Consider the word Hello.
char name[] = "Hello";
Internally, C stores the characters followed by the null character:
| Index | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| Character | H | e | l | l | o | \0 |
📝 Declaring a String
A string can be declared using a character array.
char name[20];
This creates space for up to 19 visible characters plus the terminating '\0'.
You can also initialize a string immediately:
char name[] = "Rahul";
🖥️ Printing a String
The %s format specifier is used to print a string.
#include <stdio.h>
int main()
{
char name[] = "Rahul";
printf("Name = %s", name);
return 0;
}
Output:
⌨️ Taking String Input
A simple way to read a single word is using scanf() with %s.
#include <stdio.h>
int main()
{
char name[50];
printf("Enter your name: ");
scanf("%49s", name);
printf("Hello %s", name);
return 0;
}
Notice that we do not use & before the array name in this example.
scanf("%s", ...) normally reads only up
to whitespace. For a full sentence containing spaces, use
fgets().
📖 Reading a Full Line with fgets()
If the user enters a sentence such as "I love computer programming", fgets() is a better choice.
#include <stdio.h>
int main()
{
char message[100];
printf("Enter a message: ");
fgets(message, sizeof(message), stdin);
printf("You entered: %s", message);
return 0;
}
🛠️ Important String Functions
C provides several useful functions for working with strings through the <string.h> library.
| Function | Purpose | Example |
|---|---|---|
| strlen() | Finds string length | strlen(name) |
| strcpy() | Copies a string | strcpy(a,b) |
| strcmp() | Compares strings | strcmp(a,b) |
| strcat() | Joins strings | strcat(a,b) |
📏 strlen() – Find String Length
The strlen() function returns the number of characters in a string, excluding the terminating '\0'.
#include <stdio.h>
#include <string.h>
int main()
{
char name[] = "Computer";
printf("Length = %zu", strlen(name));
return 0;
}
Output:
📋 strcpy() – Copy a String
#include <stdio.h>
#include <string.h>
int main()
{
char source[] = "Programming";
char destination[30];
strcpy(destination, source);
printf("%s", destination);
return 0;
}
Here, the contents of source are copied into destination.
⚖️ strcmp() – Compare Two Strings
The strcmp() function compares two strings.
#include <stdio.h>
#include <string.h>
int main()
{
char a[] = "Hello";
char b[] = "Hello";
if(strcmp(a, b) == 0)
{
printf("Strings are equal");
}
else
{
printf("Strings are different");
}
return 0;
}
==. Use strcmp().
🔗 strcat() – Join Two Strings
#include <stdio.h>
#include <string.h>
int main()
{
char first[50] = "Best";
char second[] = "Programming";
strcat(first, second);
printf("%s", first);
return 0;
}
Output:
💻 Complete Practical Example
Let's create a small program that asks for a user's name and displays its length.
#include <stdio.h>
#include <string.h>
int main()
{
char name[50];
printf("Enter your name: ");
fgets(name, sizeof(name), stdin);
printf("\nYour name is: %s", name);
printf("Number of characters: %zu", strlen(name));
return 0;
}
⚠️ Common Beginner Mistakes
- Forgetting to include
<string.h>when needed. - Confusing a character with a string.
- Forgetting the terminating null character when manually creating strings.
- Using an array that is too small for the intended text.
- Trying to compare strings using
==.
🔤 Character vs String
| Character | String |
|---|---|
'A' |
"Apple" |
| Uses single quotes | Uses double quotes |
| One character | Multiple characters |
char grade = 'A'; |
char name[] = "Apple"; |
🌍 Where Are Strings Used?
- 👤 User names
- 🔐 Passwords and authentication data
- 📧 Email addresses
- 💬 Messages and comments
- 📄 Text processing
- 🌐 Website and application data
🚀 Practice Programs
- Take the user's name and display it.
- Find the length of a string.
- Count the number of vowels in a string.
- Reverse a string.
- Compare two strings.
- Copy one string into another.
- Join two strings together.
- Check whether a word is a palindrome.
🧠 Quick Revision
- String: Sequence of characters ending with
'\0'. - %s: Used to print a string.
- fgets(): Useful for reading a complete line.
- strlen(): Finds string length.
- strcpy(): Copies a string.
- strcmp(): Compares two strings.
- strcat(): Joins strings.
🎯 Conclusion
Strings are essential whenever a program needs to work with text. Understanding character arrays and standard string functions will make it much easier to build useful C programs.
You now know how to declare, input, display, compare, copy and join strings in C.
