C++ Deck 8

Question 1

What is a c-string?

Answer 1

A char array that ends with the null character ‘\0’

Question 2

What is null termination?

Answer 2

Since array size needs to be known at compile time, the null character \0 is inserted at the end of a c-string array to let the compiler know that the string has ended (even if all allocated spaces in the array are not currently used.)

Question 3

What are three things that a c-string can do that a typical integer array cannot?

Answer 3

1. Directly initialize with a quoted literal.
2. Directly print with cout (no loop required)
3. Directly read one “word” with cin (again, no loop required)

Question 4

Can a c-string store character literals in single quotes such as ‘a’, ‘\n’, and ‘$’?

Answer 4

Yes.

Question 5

What does the function:

int toupper(int c)

do?

Answer 5

Returns the uppercase version of c if it’s a lowercase letter, otherwise returns c as-is

Question 6

What does the function:

int tolower(int c)

do?

Answer 6

Returns the lowercase version of c if it’s an uppercase letter, otherwise returns c as-is.

Question 7

What does the function:

int isdigit(int c)

do?

Answer 7

Determines whether the parameter is a digit (0-9) and returns true or false based on the result.

Question 8

What does the function:

int isalpha(int c)

do?

Answer 8

Determines whether the character is a letter (a-z, A-Z) and returns true or false depending on the result.

Question 9

What does the function:

int isdigit(int c)

do?

Answer 9

Determines whether or not c is a letter OR a number and returns true or false based on the result.

Question 10

What does the function:

int islower(int c)

do?

Answer 10

Determines whether or not the character is lowercase and returns true or false based on the result.

Question 11

What does the function:

int isupper(int c)

do?

Answer 11

Determines whether or not c is uppercase and returns true or false based on the result.

Question 12

What does the function:

int isxdigit(int c)

do?

Answer 12

Determines whether or not a c is a hex character (0-9, a-f) and returns true or false as a result.

Question 13

What does the function:

int isspace(int c)

do?

Answer 13

Determines whether or not c is a whitespace character and returns true or false based on the result.

Question 14

What does the function:

int iscntrl(int c)

do?

Answer 14

Determines whether or not c is a control character (e.g. ‘\n’) and returns true or false based on the result.

Question 15

What does the function:

int ispunct(int c)

do?

Answer 15

Determines whether or not c is a printable character (other than a space, letter, or digit) and returns true or false based on the result.

Question 16

What does the function:

int isprint(int c)

do?

Answer 16

Determines whether or not c is a printable character (including space) and returns true or false based on the result.

Question 17

What does the function:

int isgraph(int c)

do?

Answer 17

Determines whether or not c is a printable character (excluding space) and returns true or false based on the result.

Question 18

What is the standard string library in C?

Answer 18

<cstring>
</cstring>

Question 19

What does the function:

int strlen(const char str[]);

do?

Answer 19

Returns the length of the target string.

cout &laquo_space;strlen(“Greetings, Earthling!”); // returns 12

char phrase[30] = “Hello, World”;
int length = strlen(phrase); // stores 12

Question 20

What does the function:

char* strcpy(char str1[], const char str2[]);

do?

Answer 20

Copies the contents of the second string (which is constant and unchanged) into the first string, which is non-constant.

strcpy(firstname, “Billy Joe Bob”); // copies name into firstname array

char buffer[80], lastname[30] = “Smith”;
strcpy(buffer, lastname); // copies “Smith” into buffer array

Question 21

What does the function:

char* strcat(char str1[], const char str2[]);

do?

Answer 21

Concatenates the second string onto the first.

char buffer[30] = “Batman”
strcat(buffer, “ is awesome.”); // buffer is now: “Batman is awesome.”

Question 22

What does the function:

int strcmp(const char str1[], const char str2[]);

do?

Answer 22

Returns a negative number if str1 comes before str2, a positive number if str2 comes before str1, and a 0 if they are equal.

Lexicographic order is determined by ASCII codes and not alphabetic order. Any uppercase letter has precedence over any lower case in ASCII. Z comes before a, for example.

Question 23

What do strncpy, strncat, and strncmp do?

Answer 23

The same things as strcpy, strcat, and strcmp, but they have a built-in memory safe parameter that allows you specify a stopping point other than the null character.

Question 24

What is the priority of lexicographic ordering?

Answer 24

numeral characters -> uppercase characters -> lowercase characters