String comparison - Cheat Sheet & Quick Revision

Recall & Review

beginner

What function is commonly used in C to compare two strings?

The strcmp() function is used to compare two strings in C. It returns 0 if the strings are equal.

beginner

What does strcmp() return if the first string is lexicographically less than the second?

It returns a negative integer if the first string is less than the second string in dictionary order.

beginner

How do you check if two strings are equal using strcmp()?

You check if strcmp(str1, str2) == 0. If true, the strings are equal.

beginner

Why can't you use the == operator to compare strings in C?

Because == compares the memory addresses (pointers) of the strings, not their content.

beginner

What header file must you include to use strcmp()?

You must include <string.h> to use strcmp().

What does strcmp(str1, str2) return if str1 and str2 are exactly the same?

A -1

B 0

C 1

D The length of the strings

strcmp() returns 0 when both strings are equal.

Which header file is required to use strcmp() in C?

A <code>&lt;string.h&gt;</code>

B <code>&lt;stdio.h&gt;</code>

C <code>&lt;stdlib.h&gt;</code>

D <code>&lt;math.h&gt;</code>

<string.h> contains the declaration for strcmp().

Why is using == to compare strings in C usually incorrect?

A It compares memory addresses, not content

B It converts strings to integers

C It causes a syntax error

D It compares string lengths

== compares pointers (memory addresses), not the actual string content.

If strcmp(str1, str2) returns a positive number, what does it mean?

A Strings are equal

B <code>str1</code> is lexicographically less than <code>str2</code>

C <code>str1</code> is lexicographically greater than <code>str2</code>

D An error occurred

A positive return means str1 comes after str2 in dictionary order.

Which of these is the correct way to check if two strings a and b are equal?

A if (a == b)

B if (strcmp(a, b) != 0)

C if (a > b)

D if (strcmp(a, b) == 0)

Use strcmp(a, b) == 0 to check if strings are equal.

Explain how to compare two strings in C and why you cannot use the == operator.

Think about what <code>==</code> does with pointers.

Describe the meaning of the return values of strcmp() when comparing two strings.

Consider dictionary order comparison.