C Programming Strings Overview
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Questions and Answers

What is the return value of strcmp() when two strings are identical?

  • -1
  • 0 (correct)
  • 2
  • 1

Which header file is required to use the strcat() function?

  • <stdlib.h>
  • <stdio.h>
  • <ctype.h>
  • <string.h> (correct)

What does the strcat() function do in C programming?

  • Finds the length of a string
  • Compares two strings
  • Concatenates two strings (correct)
  • Copies one string to another

What is the correct way to declare a string in C?

<p>char str[] = &quot;Hello&quot;; (C)</p> Signup and view all the answers

What happens if the destination array in strcat() is not large enough?

<p>It causes a buffer overflow (A)</p> Signup and view all the answers

How can you manually copy a string without using strcpy()?

<p>Use loops to iterate over each character (A)</p> Signup and view all the answers

What will the output of strcmp(str1, str2) be if str1 = "abcd" and str2 = "abCd"?

<p>1 (A)</p> Signup and view all the answers

What data type is returned by the strcat() function?

<p>char * (D)</p> Signup and view all the answers

What happens when the input contains a space in the scanf() function?

<p>Only the part before the space is stored. (B)</p> Signup and view all the answers

Why don't we use '&' with the char array in scanf()?

<p>The array name automatically points to the address of the first element. (C)</p> Signup and view all the answers

What is the return type of the strlen() function?

<p>size_t (A)</p> Signup and view all the answers

What is the purpose of the strcpy() function?

<p>To copy one string to another. (B)</p> Signup and view all the answers

What will be the output of strlen() for the string 'Hello'?

<p>5 (B)</p> Signup and view all the answers

Which header file is required for using standard string functions like strcpy() and strlen()?

<p>&lt;string.h&gt; (B)</p> Signup and view all the answers

What does the strcat() function do?

<p>It concatenates two strings. (B)</p> Signup and view all the answers

What is the correct syntax for the strcpy() function?

<p>char strcpy(char* destination, const char* source); (D)</p> Signup and view all the answers

What is the correct way to declare a string in C programming?

<p>char s[5]; (A)</p> Signup and view all the answers

Which statement is true about string initialization in C?

<p>char c[] = 'hi'; (A)</p> Signup and view all the answers

What will happen if you try to assign a string to a declared char variable in C?

<p>It will throw a compile-time error. (B)</p> Signup and view all the answers

What function can be used to read a string input from the user?

<p>scanf() (D)</p> Signup and view all the answers

Which of the following string initializations is incorrect?

<p>char c = &quot;abc&quot;; (B), char c[] = 'abcd'; (C)</p> Signup and view all the answers

How does the compiler treat a string enclosed in double quotation marks?

<p>It appends a null character at the end. (A)</p> Signup and view all the answers

In which scenario will you likely encounter an error regarding string declaration?

<p>Trying char c = &quot;Too many characters&quot;; (C)</p> Signup and view all the answers

Which of the following operations is NOT valid for strings in C?

<p>Using the assignment operator after declaration. (D)</p> Signup and view all the answers

Flashcards

strcpy()

Copies a string from one variable to another.

strcmp()

Compares two strings character by character.

strcmp() return value

Returns 0 if strings are equal, non-zero otherwise.

strcat()

Joins two strings together.

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String Copy (without strcpy())

Copying a string without using the strcpy() function.

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Character-by-character Comparison

strcmp() compares strings by comparing individual characters.

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String Concatenation

Joining strings together.

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String

An array of characters terminated by a null character.

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Why was only "Dennis" stored?

The input string "Dennis Ritchie" contained a space, which caused the scanf function to read only characters until the space. The 's' format specifier in the scanf function stops reading characters when it encounters whitespace.

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Why is '&' not used with 'name' in scanf?

The variable 'name' is a character array, and in C, array names decay to pointers. Thus, the 'name' in scanf() directly refers to the address of the first element of the array, making '&' unnecessary.

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What does strlen() do?

The strlen() function calculates the length of a string, excluding the null terminator ('\0'). It takes a string as input and returns an unsigned integer representing the number of characters in the string.

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What is the return type of strlen()?

strlen() function returns a value of type size_t, which is an unsigned integer data type.

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What is the purpose of strcpy()?

The strcpy() function copies a string from one location in memory to another. It takes two arguments: the destination where the string will be copied and the source string to be copied.

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What does strcpy() return?

The strcpy() function returns a pointer to the destination string, which is the string that was copied.

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What does strcmp() do?

The strcmp() function compares two strings character by character. It returns 0 if the strings are identical, a negative value if the first string is lexicographically smaller, and a positive value if the first string is lexicographically larger.

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What does strcat() do?

The strcat() function concatenates two strings. It appends the second string to the end of the first string.

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String in C

A sequence of characters in C, ending with a null character '\0'.

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Declaring a String

Creating a string variable in C using the 'char' data type followed by an array name and size.

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Initializing a String

Assigning values to a string variable when it is declared, using double quotes or individual characters and a null terminator.

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Why is initializing with {} important?

Initializes a string by explicitly defining each character in the array, ensuring the null terminator ('\0') is included to explicitly mark the end of the string.

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Why can't you assign strings directly?

C doesn't allow direct assignment of string arrays using the '=' operator because they are second-class citizens.

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Reading a string from the user

Using the 'scanf()' function to input a sequence of characters from the user, until a whitespace character is encountered.

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What is the null character important for?

The null character ('\0') marks the end of a string, helping C functions know where the string ends and prevent unexpected behavior.

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How should you read a string from the user?

Use the 'fgets()' function instead of 'scanf()' to capture the entire string, including whitespace. This function reads the entire string until it encounters a newline character.

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Study Notes

Strings

  • Strings in C are sequences of characters terminated by a null character (\0).
  • When enclosed in double quotes, the compiler automatically adds the null character.
  • Example: char c[] = "cstring";
  • Declaring a string of 5 characters: char s[5];
  • Initializing strings: Various methods exist.
    • char c[] = "abcd";
    • char c[50] = "abcd";
    • char c[] = {'a', 'b', 'c', 'd', '\0'};
    • char c[5] = {'a', 'b', 'c', 'd', '\0'};
  • Important: Avoid assigning strings longer than the declared array size (e.g., char c[5] = "abcde";). This is incorrect and will lead to issues.
  • Arrays and strings are not assignable in C after declaration (e.g., char c[100]; c = "C programming"; is incorrect).
  • Reading strings: Use scanf("%s", name); to read a string from the user, but this stops at whitespace.

Standard Library String Functions

  • strlen(): Calculates the length of a given string.

    • Returns a size_t value (an unsigned integer).
    • Defined in <string.h>.

  • strcpy(): Copies a string to another.

    • Takes two arguments: destination string, source string, both of type char.
    • Copies the source until the null terminator.
    • Returns the copied string (destination string).
    • Defined in <string.h>

  • strcmp(): Compares two strings character by character.

    • Returns 0 if they are equal.
    • Returns a non-zero value if they're not equal. Positive if the first string is lexicographically larger.
    • Defined in <string.h>.

  • strcat(): Concatenates (joins) two strings.

    • Takes the destination and the source strings as arguments (destination needs space for the combined string).
    • Adds the source string to the end of the destination string.
    • Returns a pointer to the destination string (which is now modified).
    • Defined in <string.h>.

String Operations without Library Functions

  • Copying a string: Use loops to copy characters one by one, ensuring the destination string has enough space. Handles truncation if the destination is shorter.
  • Finding string length: Use a loop to count characters until the null terminator is found.

Structures

  • Structures are used to group variables of different data types together.

  • Example: struct employee {int id; char name[100]; float salary;};

  • Declaring a structure variable: struct employee emp1;

  • Accessing structure members: Use the dot operator: emp1.id = 101; strcpy(emp1.name,"John Doe");

  • Declaring a structure with variables: struct employee emp1, emp2;

  • Data types used:

  • int, char, float, double, etc.

  • Array of Structures:

    • Stores multiple structures.
    • Used to store data about collections of different entities.
    • Example: struct student st[5]; for storing information about 5 students.

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Unit Iv Strings And Structure PDF

Description

This quiz covers the fundamentals of strings in C programming, including their declaration, initialization, and the use of standard library string functions. Test your understanding of string characteristics and the importance of null termination in C.

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