C Programming Chapter 6: Strings

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Questions and Answers

What does the function `strcpy(s1, s2)` accomplish?

It copies string s2 into string s1. (correct)

It concatenates string s2 onto string s1.

It converts string s2 to uppercase.

It compares two strings for equality.

Which function would you use to combine two strings?

sprintf(s, format, ...)

strcmp(s1, s2)

strcat(s1, s2) (correct)

strlwr(s1)

What value does `strcmp(s1, s2)` return if s1 is lexicographically greater than s2?

An undefined value

A positive number (correct)

A negative number

What is the purpose of the function `sscanf(s, c,...)`?

To read formatted input from a string. Signup and view all the answers

Which function is used to convert a string to a floating point number?

atof(s) Signup and view all the answers

What does the C compiler do when a literal string is declared?

Appends a null character implicitly. Signup and view all the answers

What happens when scanf() encounters a whitespace while reading a string?

It stops reading and stores the string up to that point. Signup and view all the answers

What does the %10s format specifier do when printing a string?

Adds spaces before the string to reach a total length of 10. Signup and view all the answers

What is the role of the ' ' character in the function gets()?

Marks the end of the input string. Signup and view all the answers

When using %s format specifier in scanf, what might happen if the input string exceeds the defined width?

The excess characters will be ignored. Signup and view all the answers

Which function can read an entire line of input in C?

gets() Signup and view all the answers

What is the effect of using %-10s in printf?

Left aligns the string and fills spaces after it. Signup and view all the answers

Why is the '&' operator not required before a string variable when using scanf?

The name of the string acts as a pointer to the base address. Signup and view all the answers

What character is used to terminate a string in C?

'0' Signup and view all the answers

How is a string defined in C?

As an array of characters terminated with a null character Signup and view all the answers

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

char str_name[size]; Signup and view all the answers

Which of the following is NOT a valid way to initialize a string in C?

char S = "abcd"; Signup and view all the answers

What does the declaration 'char S[] = {'a', 'b', 'c', 'd', ' '};' represent?

A character array with a terminating null character Signup and view all the answers

Which of the following correctly describes the difference between a character and a string?

A string is an array of characters with a terminating null character, while a character is a single value. Signup and view all the answers

If a string is initialized using char S[] = "Hello";, what will be the memory layout?

H E L L O null Signup and view all the answers

When declaring a string variable, what does 'size' represent?

The number of characters the string can store, excluding the null character Signup and view all the answers

What is a method to terminate a loop while traversing a string?

Using the null character Signup and view all the answers

What will the following statement compile to: 'char string1 = “hello”; char string2 = “hello”; if(string1 == string2)'?

It results in a compile error Signup and view all the answers

Which function would you use to find the length of a string in C?

strlen() Signup and view all the answers

In the provided frequency algorithm, what is the initial value set for frequency?

0 Signup and view all the answers

When traversing a string using a loop, which condition keeps the loop running?

str[i] != 0 Signup and view all the answers

Why does using '==' operator compare two strings incorrectly in C?

It compares their addresses in memory Signup and view all the answers

What should be done to read a string input correctly in C?

Use scanf with a format specifier Signup and view all the answers

Which header file must be included to use string functions in C?

<string.h> Signup and view all the answers

Study Notes

Chapter 6: Strings

Strings in C are arrays of characters terminated by a null character ('\0').
The compiler automatically adds '\0' to the end of a string literal.
A string literal is a sequence of characters enclosed in double quotes.
String literals are represented by sequences of characters between double quotes.

String vs. Character

A single character, like 'H', is stored in 1 byte (ASCII value).
A string, like "H", is an array of character values, including the terminating '\0'.

String Declaration

Declare a string like a one-dimensional array: char str_name[size];
size determines the string's maximum length (number of characters).

String Initialization

Strings can be initialized in several ways:
- Using string literals: char str[] = "Hello"; (compiler adds '\0')
- Using character array initialization: char str[6] = {'H', 'e', 'l', 'l', 'o', '\0'};
Indexes start from 0.

String Initialization Differences

Defining literal strings automatically adds the null terminator.
Character arrays need an explicit null terminator.

String Input/Output

scanf("%s", variable_name) reads input until a space.
printf("%s", variable_name) displays the string.
Using scanf("%[^\n]s", variable_name) allows reading strings that contain spaces.

String Input/Output (Using Width)

scanf("%10s", variable_name) limits input to 10 characters.
Using & before the variable in scanf can be used to solve issues when reading strings that contain spaces

String Input/Output (Using gets() and puts())

gets(variable_name) reads an entire line of input. (Note: potentially unsafe, use with caution).
puts(variable_name) displays a string followed by a newline.

Traversing a String

Traversing a string can be done using either:
- The string length using strlen().
- The null terminator ('\0').
These are useful when you need to process each character in a string.

String Functions

strlen(s): Returns the length of string s.
strlwr(s): Converts all uppercase characters in s to lowercase.
strupr(s): Converts all lowercase characters in s to uppercase.
strcpy(s1, s2): Copies string s2 to string s1.
strcat(s1, s2): Appends string s2 to the end of s1.
strcmp(s1, s2): Compares s1 and s2 lexicographically (returns 0 if equal, <0 if s1 < s2, >0 if s1 > s2).
sprintf(s, format, ...): Formats and sends output to the s string.
sscanf(s, format, ...): Parses formatted input from s.
atoi(s): Converts string s to an integer.
atof(s): Converts string s to a floating-point number.

Exercises

Program examples showcasing how to use these string functions are included.

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Description

Explore the intricacies of strings in C programming through this quiz. Learn about string declarations, initializations, and the differences between strings and characters. Test your understanding of how strings are handled in C, accompanied by key concepts and examples.