c language string assignment

C String – How to Declare Strings in the C Programming Language

Computers store and process all kinds of data.

Strings are just one of the many forms in which information is presented and gets processed by computers.

Strings in the C programming language work differently than in other modern programming languages.

In this article, you'll learn how to declare strings in C.

Before doing so, you'll go through a basic overview of what data types, variables, and arrays are in C. This way, you'll understand how these are all connected to one another when it comes to working with strings in C.

Knowing the basics of those concepts will then help you better understand how to declare and work with strings in C.

Let's get started!

Data types in C

C has a few built-in data types.

They are int , short , long , float , double , long double and char .

As you see, there is no built-in string or str (short for string) data type.

The char data type in C

From those types you just saw, the only way to use and present characters in C is by using the char data type.

Using char , you are able to to represent a single character – out of the 256 that your computer recognises. It is most commonly used to represent the characters from the ASCII chart.

The single characters are surrounded by single quotation marks .

The examples below are all char s – even a number surrounded by single quoation marks and a single space is a char in C:

Every single letter, symbol, number and space surrounded by single quotation marks is a single piece of character data in C.

What if you want to present more than one single character?

The following is not a valid char – despite being surrounded by single quotation marks. This is because it doesn't include only a single character inside the single quotation marks:

'freeCodeCamp is awesome'

When many single characters are strung together in a group, like the sentence you see above, a string is created. In that case, when you are using strings, instead of single quotation marks you should only use double quotation marks.

"freeCodeCamp is awesome"

How to declare variables in C

So far you've seen how text is presented in C.

What happens, though, if you want to store text somewhere? After all, computers are really good at saving information to memory for later retrieval and use.

The way you store data in C, and in most programming languages, is in variables.

Essentially, you can think of variables as boxes that hold a value which can change throughout the life of a program. Variables allocate space in the computer's memory and let C know that you want some space reserved.

C is a statically typed language, meaning that when you create a variable you have to specify what data type that variable will be.

There are many different variable types in C, since there are many different kinds of data.

Every variable has an associated data type.

When you create a variable, you first mention the type of the variable (wether it will hold integer, float, char or any other data values), its name, and then optionally, assign it a value:

Be careful not to mix data types when working with variables in C, as that will cause errors.

For intance, if you try to change the example from above to use double quotation marks (remember that chars only use single quotation marks), you'll get an error when you compile the code:

As mentioned earlier on, C doesn't have a built-in string data type. That also means that C doesn't have string variables!

How to create arrays in C

An array is essentially a variable that stores multiple values. It's a collection of many items of the same type.

As with regular variables, there are many different types of arrays because arrays can hold only items of the same data type. There are arrays that hold only int s, only float s, and so on.

This is how you define an array of ints s for example:

First you specify the data type of the items the array will hold. Then you give it a name and immediately after the name you also include a pair of square brackets with an integer. The integer number speficies the length of the array.

In the example above, the array can hold 3 values.

After defining the array, you can assign values individually, with square bracket notation, using indexing. Indexing in C (and most programming languages) starts at 0 .

You reference and fetch an item from an array by using the name of the array and the item's index in square brackets, like so:

What are character arrays in C?

So, how does everything mentioned so far fit together, and what does it have to do with initializing strings in C and saving them to memory?

Well, strings in C are actually a type of array – specifically, they are a character array . Strings are a collection of char values.

How strings work in C

In C, all strings end in a 0 . That 0 lets C know where a string ends.

That string-terminating zero is called a string terminator . You may also see the term null zero used for this, which has the same meaning.

Don't confuse this final zero with the numeric integer 0 or even the character '0' - they are not the same thing.

The string terminator is added automatically at the end of each string in C. But it is not visible to us – it's just always there.

The string terminator is represented like this: '\0' . What sets it apart from the character '0' is the backslash it has.

When working with strings in C, it's helpful to picture them always ending in null zero and having that extra byte at the end.

Each character takes up one byte in memory.

The string "hello" , in the picture above, takes up 6 bytes .

"Hello" has five letters, each one taking up 1 byte of space, and then the null zero takes up one byte also.

The length of strings in C

The length of a string in C is just the number of characters in a word, without including the string terminator (despite it always being used to terminate strings).

The string terminator is not accounted for when you want to find the length of a string.

For example, the string freeCodeCamp has a length of 12 characters.

But when counting the length of a string, you must always count any blank spaces too.

For example, the string I code has a length of 6 characters. I is 1 character, code has 4 characters, and then there is 1 blank space.

So the length of a string is not the same number as the number of bytes that it has and the amount of memory space it takes up.

How to create character arrays and initialize strings in C

The first step is to use the char data type. This lets C know that you want to create an array that will hold characters.

Then you give the array a name, and immediatelly after that you include a pair of opening and closing square brackets.

Inside the square brackets you'll include an integer. This integer will be the largest number of characters you want your string to be including the string terminator.

You can initialise a string one character at a time like so:

But this is quite time-consuming. Instead, when you first define the character array, you have the option to assign it a value directly using a string literal in double quotes:

If you want, istead of including the number in the square brackets, you can only assign the character array a value.

It works exactly the same as the example above. It will count the number of characters in the value you provide and automatically add the null zero character at the end:

Remember, you always need to reserve enough space for the longest string you want to include plus the string terminator.

If you want more room, need more memory, and plan on changing the value later on, include a larger number in the square brackets:

How to change the contents of a character array

So, you know how to initialize strings in C. What if you want to change that string though?

You cannot simply use the assignment operator ( = ) and assign it a new value. You can only do that when you first define the character array.

As seen earlier on, the way to access an item from an array is by referencing the array's name and the item's index number.

So to change a string, you can change each character individually, one by one:

That method is quite cumbersome, time-consuming, and error-prone, though. It definitely is not the preferred way.

You can instead use the strcpy() function, which stands for string copy .

To use this function, you have to include the #include <string.h> line after the #include <stdio.h> line at the top of your file.

The <string.h> file offers the strcpy() function.

When using strcpy() , you first include the name of the character array and then the new value you want to assign. The strcpy() function automatically add the string terminator on the new string that is created:

And there you have it. Now you know how to declare strings in C.

To summarize:

• C does not have a built-in string function.
• To work with strings, you have to use character arrays.
• When creating character arrays, leave enough space for the longest string you'll want to store plus account for the string terminator that is included at the end of each string in C.
• Define the array and then assign each individual character element one at a time.
• OR define the array and initialize a value at the same time.
• When changing the value of the string, you can use the strcpy() function after you've included the <string.h> header file.

If you want to learn more about C, I've written a guide for beginners taking their first steps in the language.

It is based on the first couple of weeks of CS50's Introduction to Computer Science course and I explain some fundamental concepts and go over how the language works at a high level.

You can also watch the C Programming Tutorial for Beginners on freeCodeCamp's YouTube channel.

Thanks for reading and happy learning :)

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Next: Execution Control Expressions , Previous: Arithmetic , Up: Top   [ Contents ][ Index ]

7 Assignment Expressions

As a general concept in programming, an assignment is a construct that stores a new value into a place where values can be stored—for instance, in a variable. Such places are called lvalues (see Lvalues ) because they are locations that hold a value.

An assignment in C is an expression because it has a value; we call it an assignment expression . A simple assignment looks like

We say it assigns the value of the expression value-to-store to the location lvalue , or that it stores value-to-store there. You can think of the “l” in “lvalue” as standing for “left,” since that’s what you put on the left side of the assignment operator.

However, that’s not the only way to use an lvalue, and not all lvalues can be assigned to. To use the lvalue in the left side of an assignment, it has to be modifiable . In C, that means it was not declared with the type qualifier const (see const ).

The value of the assignment expression is that of lvalue after the new value is stored in it. This means you can use an assignment inside other expressions. Assignment operators are right-associative so that

is equivalent to

This is the only useful way for them to associate; the other way,

would be invalid since an assignment expression such as x = y is not valid as an lvalue.

Warning: Write parentheses around an assignment if you nest it inside another expression, unless that is a conditional expression, or comma-separated series, or another assignment.

C Functions

C structures, c reference.

Strings are used for storing text/characters.

For example, "Hello World" is a string of characters.

Unlike many other programming languages, C does not have a String type to easily create string variables. Instead, you must use the char type and create an array of characters to make a string in C:

Note that you have to use double quotes ( "" ).

To output the string, you can use the printf() function together with the format specifier %s to tell C that we are now working with strings:

Access Strings

Since strings are actually arrays in C, you can access a string by referring to its index number inside square brackets [] .

This example prints the first character (0) in greetings :

Note that we have to use the %c format specifier to print a single character .

Modify Strings

To change the value of a specific character in a string, refer to the index number, and use single quotes :

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Loop Through a String

You can also loop through the characters of a string, using a for loop:

And like we specified in the arrays chapter, you can also use the sizeof formula (instead of manually write the size of the array in the loop condition (i < 5) ) to make the loop more sustainable:

Another Way Of Creating Strings

In the examples above, we used a "string literal" to create a string variable. This is the easiest way to create a string in C.

You should also note that you can create a string with a set of characters. This example will produce the same result as the example in the beginning of this page:

Why do we include the \0 character at the end? This is known as the "null terminating character", and must be included when creating strings using this method. It tells C that this is the end of the string.

Differences

The difference between the two ways of creating strings, is that the first method is easier to write, and you do not have to include the \0 character, as C will do it for you.

You should note that the size of both arrays is the same: They both have 13 characters (space also counts as a character by the way), including the \0 character:

Real-Life Example

Use strings to create a simple welcome message:

C Exercises

Test yourself with exercises.

Fill in the missing part to create a "string" named greetings , and assign it the value "Hello".

Start the Exercise

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Strings in C: How to Declare & Initialize a String Variables in C

What is String in C?

A String in C is nothing but a collection of characters in a linear sequence. ‘C’ always treats a string a single data even though it contains whitespaces. A single character is defined using single quote representation. A string is represented using double quote marks.

‘C’ provides standard library <string.h> that contains many functions which can be used to perform complicated operations easily on Strings in C.

How to Declare a String in C?

A C String is a simple array with char as a data type. ‘C’ language does not directly support string as a data type. Hence, to display a String in C, you need to make use of a character array.

The general syntax for declaring a variable as a String in C is as follows,

The classic Declaration of strings can be done as follow:

The size of an array must be defined while declaring a C String variable because it is used to calculate how many characters are going to be stored inside the string variable in C. Some valid examples of string declaration are as follows,

The above example represents string variables with an array size of 15. This means that the given C string array is capable of holding 15 characters at most. The indexing of array begins from 0 hence it will store characters from a 0-14 position. The C compiler automatically adds a NULL character ‘\0’ to the character array created.

How to Initialize a String in C?

Let’s study the String initialization in C. Following example demonstrates the initialization of Strings in C,

In string3, the NULL character must be added explicitly, and the characters are enclosed in single quotation marks.

‘C’ also allows us to initialize a string variable without defining the size of the character array. It can be done in the following way,

The name of Strings in C acts as a pointer because it is basically an array.

C String Input: C Program to Read String

When writing interactive programs which ask the user for input, C provides the scanf(), gets(), and fgets() functions to find a line of text entered from the user.

When we use scanf() to read, we use the “%s” format specifier without using the “&” to access the variable address because an array name acts as a pointer. For example:

The problem with the scanf function is that it never reads entire Strings in C. It will halt the reading process as soon as whitespace, form feed, vertical tab, newline or a carriage return occurs. Suppose we give input as “Guru99 Tutorials” then the scanf function will never read an entire string as a whitespace character occurs between the two names. The scanf function will only read Guru99 .

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In order to read a string contains spaces, we use the gets() function. Gets ignores the whitespaces. It stops

reading when a newline is reached (the Enter key is pressed).

For example:

Another safer alternative to gets() is fgets() function which reads a specified number of characters. For example:

The fgets() arguments are :

• the string name,
• the number of characters to read,
• stdin means to read from the standard input which is the keyboard.

C String Output: C program to Print a String

The standard printf function is used for printing or displaying Strings in C on an output device. The format specifier used is %s

String output is done with the fputs() and printf() functions.

fputs() function

The fputs() needs the name of the string and a pointer to where you want to display the text. We use stdout which refers to the standard output in order to print to the screen. For example:

puts function

The puts function is used to Print string in C on an output device and moving the cursor back to the first position. A puts function can be used in the following way,

The syntax of this function is comparatively simple than other functions.

The string library

The standard ‘C’ library provides various functions to manipulate the strings within a program. These functions are also called as string handlers. All these handlers are present inside <string.h> header file.

Lets consider the program below which demonstrates string library functions:

Other important library functions are:

• strncmp(str1, str2, n) :it returns 0 if the first n characters of str1 is equal to the first n characters of str2, less than 0 if str1 < str2, and greater than 0 if str1 > str2.
• strncpy(str1, str2, n) This function is used to copy a string from another string. Copies the first n characters of str2 to str1
• strchr(str1, c): it returns a pointer to the first occurrence of char c in str1, or NULL if character not found.
• strrchr(str1, c): it searches str1 in reverse and returns a pointer to the position of char c in str1, or NULL if character not found.
• strstr(str1, str2): it returns a pointer to the first occurrence of str2 in str1, or NULL if str2 not found.
• strncat(str1, str2, n) Appends (concatenates) first n characters of str2 to the end of str1 and returns a pointer to str1.
• strlwr() :to convert string to lower case
• strupr() :to convert string to upper case
• strrev() : to reverse string

Converting a String to a Number

In C programming, we can convert a string of numeric characters to a numeric value to prevent a run-time error. The stdio.h library contains the following functions for converting a string to a number:

• int atoi(str) Stands for ASCII to integer; it converts str to the equivalent int value. 0 is returned if the first character is not a number or no numbers are encountered.
• double atof(str) Stands for ASCII to float, it converts str to the equivalent double value. 0.0 is returned if the first character is not a number or no numbers are encountered.
• long int atol(str) Stands for ASCII to long int, Converts str to the equivalent long integer value. 0 is returned if the first character is not a number or no numbers are encountered.

The following program demonstrates atoi() function:

• A string pointer declaration such as char *string = “language” is a constant and cannot be modified.
• A string is a sequence of characters stored in a character array.
• A string is a text enclosed in double quotation marks.
• A character such as ‘d’ is not a string and it is indicated by single quotation marks.
• ‘C’ provides standard library functions to manipulate strings in a program. String manipulators are stored in <string.h> header file.
• A string must be declared or initialized before using into a program.
• There are different input and output string functions, each one among them has its features.
• Don’t forget to include the string library to work with its functions
• We can convert string to number through the atoi(), atof() and atol() which are very useful for coding and decoding processes.
• We can manipulate different strings by defining a array of strings in C.

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You need to often manipulate strings according to the need of a problem. Most, if not all, of the time string manipulation can be done manually but, this makes programming complex and large.

To solve this, C supports a large number of string handling functions in the standard library "string.h" .

Few commonly used string handling functions are discussed below:

String handling functions are defined under "string.h" header file.

Note: You have to include the code below to run string handling functions.

gets() and puts()

Functions gets() and puts() are two string functions to take string input from the user and display it respectively as mentioned in the  previous chapter .

Note: Though, gets() and puts() function handle strings, both these functions are defined in "stdio.h" header file.

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Strings in C Programming Language (With Examples)

Strings in C programming language: In this tutorial, we will learn about the strings in C, declaring, initializing, printing getting the length of the string, and many more with the help of examples. By Sneha Dujaniya Last updated : December 26, 2023

What are Strings ?

Strings are mostly considered difficult by many beginners but trust me, Strings are no big deal. A string is nothing but a group of characters stored in a character array. Character arrays are used in programming languages to manipulate words and sentences.

A string is a constant in the form of the one-dimensional array of characters terminated by a null character which is \0 . Example,

Points to be noted:

• Memory space occupied by each character is one byte and the last character has to be null \0 .
• \0 should not be confused with the digit 0 since the ASCII value of null is 0 whereas that of ‘0' is 48.
• The members of the array are stored in contiguous memory locations as shown below.

• The null character at the end is very important because that is the only way for the compiler to know where the string ends. But to be noted, the null declaration is not necessary. It is inserted by the compiler automatically as in the following example: char city[] = "TOKYO";
• The format specification used for printing and receiving a string is "%s" .

Declaring String

The string is a character array. Thus, to declare a string, you need to create a character array with the maximum size of the string.

Declare a string to store a name.

Initialize String

There are multiple methods to initialize string.

1. Initialize string during declaration

You can initialize a string during declaration in the following ways:

2. Initialize string by using strcpy() or memcpy()

You cannot directly assign a string by using the assignment ( = ) operator. You can initialize a string anywhere in the program after the declaration by using either strcpy() or memcpy() function .

To use strcpy() or memcpy() function, you need to include <string.h> header file .

Printing String

To print a string in language, you can use printf() and puts() functions. The printf() function requires "%s" format specifier to display the string value whereas the puts() function just takes the string variable as an argument.

Printing String Variable Size

To print the occupied memory size (in bytes) by a string variable, you can use the sizeof() operator .

You can see, that we used "%ld" in the printf() statement. The "%ld" is a format specifier to display the long int value. The sizeof() operator returns a long integer value.

Also Read: Arguments for printf() that formats a long datatype

Getting String Length

There are two ways to get the string length: Using the strlen() method (which is a library function of string.h header), and by counting each character of the string using the loop (for that you can create a function to get the string length ).

C Strings: More Examples

Now let us see some of the examples:

Example 1: Declare string and print character by character

Simple program, where we are treating the string as a character array and we use %c in printf() statement . Also, the length of the word is taken to be 4 because the value of the first element in an array is always assigned 0 , as we all know already. But this solution is not profitable if we have a bigger string.

So, here is another way to do it:

Example 2: Declare string and print character by character till NULL not found

Example 3: declaring string and printing as string (using "%s" format specifier).

This was the simplest way to print a string using the general specification of %s .

Example 4: Reading string using scanf() function

Here, the declaration char city[15] stores 15 bytes of memory under the array city[] . Whereas, the scanf() function fills the characters entered till the enter key is pressed by the user. After that, scanf() automatically adds a null character leaving the further memory blank.

Reading a string using scanf() or gets()?

Points to be kept in mind while using scanf():

• The length of the string entered by the user should not exceed the value declared in the array since C compilers do not show any Array index out of bound error for this. It will simply result in the overwriting of important data.
• Using scanf() , we can't enter a multi-word string, for example, "New York". This problem can be resolved by using the function gets() and puts() as shown below,

Use of gets() and puts()

Here, puts() can display only one string at a time therefore, two puts() statements are used. Also, unlike printf() , it places the cursor automatically to the next line.

Though gets() can receive only one string at a time, still it is preferable as it can receive multi-word strings .

Author's note:

This was a basic of what strings actually are. In the next article, I will write about string manipulations and standard library string functions . For better understanding, practice these codes on your own by changing the values and outputs. I'm ready to help if the case of queries. Happy coding!

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String and Character Array in C

String is a sequence of characters that are treated as a single data item and terminated by a null character '\0' . Remember that the C language does not support strings as a data type. A string is actually a one-dimensional array of characters in C language. These are often used to create meaningful and readable programs.

If you don't know what an array in C means, you can check the C Array tutorial to know about Array in the C language. Before proceeding further, check the following articles:

C Function Calls

C Variables

C Datatypes

For example: The string "home" contains 5 characters including the '\0' character which is automatically added by the compiler at the end of the string.

Declaring and Initializing String variables in C

Let's see how you can declare and initialize a string variable in C language.

String Input and Output in C

%s format specifier to read a string input from the terminal.

But scanf() function, terminates its input on the first white space it encounters.

edit set conversion code %[..] that can be used to read a line containing a variety of characters, including white spaces.

The gets() function can also be used to read character string with white spaces

Let's see a code example now,

We can also ue gets function to get the string as input.

String Handling Functions in C

C language supports a large number of string handling functions that can be used to carry out many of the string manipulations. These functions are packaged in the string.h library. Hence, you must include string.h header file in your programs to use these functions.

The following are the most commonly used string handling functions.

There are many more String functions, but in this tutorial we will learn how to use the above mentioned string functions.

1. strcat() function

strcat() will add the string "world" to "hello" i.e ouput = helloworld.

2. strlen() and strcmp() function

strlen() will return the length of the string passed to it and strcmp() will return the ASCII difference between first unmatching character of two strings.

3. strcpy() function

It copies the second string argument to the first string argument.

let's see an example of strcpy() function,

StudyTonight

4. strrev() function:

It is used to reverse the given string expression.

Code snippet for strrev() :

Enter your string: studytonight Your reverse string is: thginotyduts

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C Exercises – Practice Questions with Solutions for C Programming

The best way to learn C programming language is by hands-on practice. This C Exercise page contains the top 30 C exercise questions with solutions that are designed for both beginners and advanced programmers. It covers all major concepts like arrays, pointers, for-loop, and many more.

So, Keep it Up! Solve topic-wise C exercise questions to strengthen your weak topics.

C Programming Exercises

The following are the top 30 programming exercises with solutions to help you practice online and improve your coding efficiency in the C language. You can solve these questions online in GeeksforGeeks IDE.

Q1: Write a Program to Print “Hello World!” on the Console.

In this problem, you have to write a simple program that prints “Hello World!” on the console screen.

For Example,

Click here to view the solution.

Q2: write a program to find the sum of two numbers entered by the user..

In this problem, you have to write a program that adds two numbers and prints their sum on the console screen.

Q3: Write a Program to find the size of int, float, double, and char.

In this problem, you have to write a program to print the size of the variable.

Q4: Write a Program to Swap the values of two variables.

In this problem, you have to write a program that swaps the values of two variables that are entered by the user.

Swap two numbers

Q5: Write a Program to calculate Compound Interest.

In this problem, you have to write a program that takes principal, time, and rate as user input and calculates the compound interest.

Q6: Write a Program to check if the given number is Even or Odd.

In this problem, you have to write a program to check whether the given number is even or odd.

Q7: Write a Program to find the largest number among three numbers.

In this problem, you have to write a program to take three numbers from the user as input and print the largest number among them.

Q8: Write a Program to make a simple calculator.

In this problem, you have to write a program to make a simple calculator that accepts two operands and an operator to perform the calculation and prints the result.

Q9: Write a Program to find the factorial of a given number.

In this problem, you have to write a program to calculate the factorial (product of all the natural numbers less than or equal to the given number n) of a number entered by the user.

Q10: Write a Program to Convert Binary to Decimal.

In this problem, you have to write a program to convert the given binary number entered by the user into an equivalent decimal number.

Q11: Write a Program to print the Fibonacci series using recursion.

In this problem, you have to write a program to print the Fibonacci series(the sequence where each number is the sum of the previous two numbers of the sequence) till the number entered by the user using recursion.

Fibonacci Series

Q12: Write a Program to Calculate the Sum of Natural Numbers using recursion.

In this problem, you have to write a program to calculate the sum of natural numbers up to a given number n.

Q13: Write a Program to find the maximum and minimum of an Array.

In this problem, you have to write a program to find the maximum and the minimum element of the array of size N given by the user.

Q14: Write a Program to Reverse an Array.

In this problem, you have to write a program to reverse an array of size n entered by the user. Reversing an array means changing the order of elements so that the first element becomes the last element and the second element becomes the second last element and so on.

Reverse an array

Q15: Write a Program to rotate the array to the left.

In this problem, you have to write a program that takes an array arr[] of size N from the user and rotates the array to the left (counter-clockwise direction) by D steps, where D is a positive integer. 

Q16: Write a Program to remove duplicates from the Sorted array.

In this problem, you have to write a program that takes a sorted array arr[] of size N from the user and removes the duplicate elements from the array.

Q17: Write a Program to search elements in an array (using Binary Search).

In this problem, you have to write a program that takes an array arr[] of size N and a target value to be searched by the user. Search the target value using binary search if the target value is found print its index else print ‘element is not present in array ‘.

Q18: Write a Program to reverse a linked list.

In this problem, you have to write a program that takes a pointer to the head node of a linked list, you have to reverse the linked list and print the reversed linked list.

Q18: Write a Program to create a dynamic array in C.

In this problem, you have to write a program to create an array of size n dynamically then take n elements of an array one by one by the user. Print the array elements.

Q19: Write a Program to find the Transpose of a Matrix.

In this problem, you have to write a program to find the transpose of a matrix for a given matrix A with dimensions m x n and print the transposed matrix. The transpose of a matrix is formed by interchanging its rows with columns.

Q20: Write a Program to concatenate two strings.

In this problem, you have to write a program to read two strings str1 and str2 entered by the user and concatenate these two strings. Print the concatenated string.

Q21: Write a Program to check if the given string is a palindrome string or not.

In this problem, you have to write a program to read a string str entered by the user and check whether the string is palindrome or not. If the str is palindrome print ‘str is a palindrome’ else print ‘str is not a palindrome’. A string is said to be palindrome if the reverse of the string is the same as the string.

Q22: Write a program to print the first letter of each word.

In this problem, you have to write a simple program to read a string str entered by the user and print the first letter of each word in a string.

Q23: Write a program to reverse a string using recursion

In this problem, you have to write a program to read a string str entered by the user, and reverse that string means changing the order of characters in the string so that the last character becomes the first character of the string using recursion. 

reverse a string

Q24: Write a program to Print Half half-pyramid pattern.

In this problem, you have to write a simple program to read the number of rows (n) entered by the user and print the half-pyramid pattern of numbers. Half pyramid pattern looks like a right-angle triangle of numbers having a hypotenuse on the right side.

Q25: Write a program to print Pascal’s triangle pattern.

In this problem, you have to write a simple program to read the number of rows (n) entered by the user and print Pascal’s triangle pattern. Pascal’s Triangle is a pattern in which the first row has a single number 1 all rows begin and end with the number 1. The numbers in between are obtained by adding the two numbers directly above them in the previous row.

Pascal’s Triangle

Q26: Write a program to sort an array using Insertion Sort.

In this problem, you have to write a program that takes an array arr[] of size N from the user and sorts the array elements in ascending or descending order using insertion sort.

Q27: Write a program to sort an array using Quick Sort.

In this problem, you have to write a program that takes an array arr[] of size N from the user and sorts the array elements in ascending order using quick sort.

Q28: Write a program to sort an array of strings.

In this problem, you have to write a program that reads an array of strings in which all characters are of the same case entered by the user and sort them alphabetically. 

Q29: Write a program to copy the contents of one file to another file.

In this problem, you have to write a program that takes user input to enter the filenames for reading and writing. Read the contents of one file and copy the content to another file. If the file specified for reading does not exist or cannot be opened, display an error message “Cannot open file: file_name” and terminate the program else print “Content copied to file_name”

Q30: Write a program to store information on students using structure.

In this problem, you have to write a program that stores information about students using structure. The program should create various structures, each representing a student’s record. Initialize the records with sample data having data members’ Names, Roll Numbers, Ages, and Total Marks. Print the information for each student.

We hope after completing these C exercises you have gained a better understanding of C concepts. Learning C language is made easier with this exercise sheet as it helps you practice all major C concepts. Solving these C exercise questions will take you a step closer to becoming a C programmer.

Frequently Asked Questions (FAQs)

Q1. what are some common mistakes to avoid while doing c programming exercises.

Some of the most common mistakes made by beginners doing C programming exercises can include missing semicolons, bad logic loops, uninitialized pointers, and forgotten memory frees etc.

Q2. What are the best practices for beginners starting with C programming exercises?

Best practices for beginners starting with C programming exercises: Start with easy codes Practice consistently Be creative Think before you code Learn from mistakes Repeat!

Q3. How do I debug common errors in C programming exercises?

You can use the following methods to debug a code in C programming exercises Read the error message carefully Read code line by line Try isolating the error code Look for Missing elements, loops, pointers, etc Check error online

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Char String Assignment

I am working on Microsoft Visual Studio environment. I came across a strange behavior

The result is:

That means the des[0] is not being initialized. As src is pointing to the first element of the string. I guess by rules this should work.

• variable-assignment

• 1 Please tag the question with the language, so people know what you are talking about. –  Oded Commented Dec 27, 2011 at 13:46
• If you're using C++, why in the world are you using printf and C-style strings? –  Cody Gray ♦ Commented Dec 27, 2011 at 13:50
• @CodyGray: Sorry. I am using C language as platform. I have edited the tag. –  Vinay Commented Dec 27, 2011 at 14:02

5 Answers 5

This is undefined behavior:

Try this instead:

• Thank you. yes, it does work. But isn't it in both the cases, des would be pointing to the same location. And eventually 'des[0]' is equivalent to '*(des+0)'. by undefined behavior, are you referring to the C specifications? –  Vinay Commented Dec 27, 2011 at 13:54
• @vinaygarg It's not the same thing. Yes, I am talking about the C standard, but I expect the C++ standards to be similar in this respect. –  cnicutar Commented Dec 27, 2011 at 13:55

Since src and des are initialized with string literals, their type should actually be const char * , not char * ; like this:

There was never memory allocated for either of them, they just point to the predefined constants. Therefore, the statement des[0] = src[0] is undefined behavior; you're trying to change a constant there!

Any decent compiler should actually warn you about the implicit conversion from const char * to char * ...

If using C++, consider using std::string instead of char * , and std::cout instead of printf .

Section 2.13.4 of ISO/IEC 14882 (Programming languages - C++) says:

A string literal is a sequence of characters (as defined in 2.13.2) surrounded by double quotes, optionally beginning with the letter L, as in "..." or L"...". A string literal that does not begin with L is an ordinary string literal, also referred to as a narrow string literal. An ordinary string literal has type “array of n const char” and static storage duration (3.7), where n is the size of the string as defined below, and is initialized with the given characters. ...

Whether all string literals are distinct (that is, are stored in nonoverlapping objects) is implementation defined. The effect of attempting to modify a string literal is undefined .

In C, string literals such as "123" are stored as arrays of char ( const char in C++). These arrays are stored in memory such that they are available over the lifetime of the program. Attempting to modify the contents of a string literal results in undefined behavior; sometimes it will "work", sometimes it won't, depending on the compiler and the platform, so it's best to treat string literals as unwritable.

Remember that under most circumstances, an expression of type "N-element array of T " will be converted to an expression of type "pointer to T " whose value is the location of the first element in the array.

Thus, when you write

the expressions "123" and "abc" are converted from "3-element array of char " to "pointer to char ", and src will point to the '1' in "123" , and des will point to the 'a' in "abc" .

Again, attempting to modify the contents of a string literal results in undefined behavior, so when you write

the compiler is free to treat that statement any way it wants to, from ignoring it completely to doing exactly what you expect it to do to anything in between. That means that string literals, or a pointer to them, cannot be used as target parameters to calls like strcpy , strcat , memcpy , etc., nor should they be used as parameters to calls like strtok .

vinaygarg : That means the des[0] is not being initialized. As src is pointing to the first element of the string. I guess by rules this should work.

Firstly you must remember that *src and *dst are defined as pointers, nothing more, nothing less.

So you must then ask yourself what exactly "123" and "abc" are and why it cannot be altered? Well to cut a long story short, it is stored in application memory, which is read-only . Why? The strings must be stored with the program in order to be available to your code at run time, in theory you should get a compiler warning for assigning a non-const char* to a const char * . Why is it read-only ? The memory for exe's and dll's need to be protected from being overwritten somehow, so it must be read-only to stop bugs and viruses from modifying executing code.

So how can you get this string into modifiable memory?

• @pmg My apologies, was not aware of C-only requirement at time of writing. Updated, thanks for pointing that out. –  Keldon Alleyne Commented Dec 27, 2011 at 14:09

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