This document discusses C strings and string functions. It defines a C string as a sequence of characters terminated with a null character. Strings are stored as character arrays. It provides examples of declaring, initializing, reading, and passing strings. It also describes common string functions like strcpy(), strcat(), strcmp(), strlen() for copying, concatenating, comparing, and getting the length of strings.

1. CSC 2O3: COMPUTER PROGRAMMING 1
Week 6:
C Strings, String Functions and Examples
DR(MRS) O.E.OJO

2. Strings in C
• A String in C programming is a sequence of characters
terminated with a null character ‘0’.
• The C String is stored as an array of characters.
• The difference between a character array and a C string is
the string is terminated with a unique character ‘0’.
• For example: In C programming, a string is a sequence of
characters terminated with a null character 0.

3. When the compiler encounters a sequence of characters enclosed
in the double quotation marks, it appends a null character 0 at the
end by default.
Memory Diagram
char c[ ] = “c string”;

4. How to declare a string
char s[5];
Here, we have declared a string of 5 characters.
Here's how you can declare strings:
String Declaration in C

5. How to initialize strings
.
char c[] = "abcd";
char c[50] = "abcd";
char c[] = {'a', 'b', 'c', 'd', '0'};
char c[5] = {'a', 'b', 'c', 'd', '0'};
String Initialization in C
You can initialize strings in a number of ways

6. Assigning values to strings
char c[100];
c = 100 “C programming”; // Error! array is not assigned
Arrays and strings are second-class citizens in C; they do not support the
assignment operator once it is declared. For example,
Note: Use the strcpy() function to copy the string instead.

7. Read string from user
• You can use the scanf() function to read a string.
• The scanf() function reads the sequence of characters
until it encounters
whitespace (space, newline, tab, etc.).

8. Example 1: scanf() to read a string
#include <stdio.h>
int main()
{
char name[20];
printf("Enter name: ");
scanf("%s", name);
printf("Your name is %s.", name);
return 0;
}

9. Read string from user (cont’d.)
Output
oluwafolakeojo@Oluwafolakes-MacBook-
Air WEEK6 % ./string1
Enter name: Mary Adeniyi
Your name is Mary.%
oluwafolakeojo@Oluwafolakes-MacBook-
Air WEEK6 %

10. Even though Mary Adeniyi was entered in the above program, only ”Mary" was
stored in the name string. It's because there was a space after Adeniyi.
Also notice that we have used the code name instead of &name with scanf().
This is because name is a char array, and we know that array names decay to
pointers in C.
Thus, the name in scanf() already points to the address of the first element in the
string, which is why we don't need to use &.
scanf("%s", name);

11. How to read a line of text?
You can use the fgets() function to read a line of string. And, you can use puts()
to display the string.
Example 2: fgets() and puts()
#include <stdio.h>
int main()
{
char name[30];
printf("Enter name: ");
fgets(name, sizeof(name), stdin); // read string
printf("Name: ");
puts(name); // display string
return 0;
}

12. Here, we have used fgets() function to read a string from the user.
fgets(name, sizeof(name), stdlin); // read string
The sizeof(name) results to 30. Hence, we can take a maximum of 30 characters as input
which is the size of the name string.
To print the string, we have used puts(name);.
Note: The gets() function can also be to take input from the user. However, it is removed
from the C standard.
It's because gets() allows you to input any length of characters. Hence, there might be a
buffer overflow.

13. Output
oluwafolakeojo@Oluwafolakes-MacBook-
Air WEEK6 % ./string2
Enter name: Mary Adeniyi
Name: Mary Adeniyi
oluwafolakeojo@Oluwafolakes-MacBook-
Air WEEK6 %

14. Passing Strings to Functions
Strings can be passed to a function in a similar way as arrays.
Example 3: Passing string to a Function
#include <stdio.h>
void displayString(char str[]);
int main()
{
char str[50];
printf("Enter string: “);

15. fgets(str, sizeof(str), stdin);
displayString(str); // Passing string to a function.
return 0;
}
void displayString(char str[ ])
{
printf("String Output: “);
puts(str);
}

16. Functions Description
strcat() Function to concatenate(merge) strings.
strcmp() Function to compare two strings.
strcpy() Function to copy a string to another string.
stricmp() Function to compare two strings ignoring their
case.
strlen() Function to calculate the length of the string.
strlwr() Converts the given string to lowercase.
strrev() Function to reverse the given string.
strupr() Converts the given string to uppercase.

17. Functions Description
strdup() Duplicates a string.
strnicmp() Compares the first n characters of one string to
another without being case sensitive.
strncat() Adds the first n characters at the end of second
string.
strncpy() Copies the first n characters of a string into another.
strchr() Finds the first occurrence of the character.
strrchr() Finds the last occurrence of the character.
strstr() Finds the first occurrence of string in another string.

18. Functions Description
strset() Sets all the characters of the string to a given
character.
strnset() Sets first n characters of the string to a given
character.

19. In this tutorial, you will learn to use the strcpy() function in C programming
to copy strings (with the help of an example).
C strcpy()
The function prototype of strcpy() is:
char* strcpy(char* destination, const char* source);
 The strcpy() function copies the string pointed by source (including the null
character) to the destination.
 The strcpy() function also returns the copied string.
The strcpy() function is defined in the string.h header file.

20. Example: C strcpy()
#include <stdio.h>
#include <string.h>
int main() {
char str1[20] = "C programming";
char str2[20];
// copying str1 to str2
strcpy(str2, str1);
puts(str2); // C programming
return 0;
}
Run Code
Output
C programming
Note: When you
use strcpy(), the size of
the destination string
should be large enough
to store the copied string.
Otherwise, it may result
in undefined behavior.