Week 4: Memory Maps / String Functions / Simple I/O

Question 1

A char takes how many bytes

Answer 1

1 byte

Question 2

An int takes how many bytes

Answer 2

4 bytes

Question 3

A float takes how many bytes?

Answer 3

4 bytes

Question 4

Do different VARIABLES have to be contiguous?

Answer 4

NO

Question 5

What is in the memory location when a variable is declared?

Answer 5

Whatever was there before

Question 6

How many statements does the computer see in the following:

int height = 8;

Answer 6

Two, one for declaration and another for initialization

Question 7

What is a “scalar” variable?

Answer 7

A variable capable of of holding a single data item

Question 8

What is an “aggregate” variable?

Answer 8

A variable capable of holding a collection of values

arrays and structures

Question 9

What are the two kinds of aggregate variables in C?

Answer 9

Arrays and structures

Question 10

What is an array initializer?

Answer 10

The contents of an array enclosed in curly brackets

{1,2,3,4,0,0,0}

Question 11

What does this do?

int a[10];

Answer 11

Declares an array of type int with 10 elements

Question 12

What does this do?

int a[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

Answer 12

Declares an array of type int with 10 elements AND what the elements are

Question 13

What does this do?

int a[10] = {1, 2, 3, 4, 5, 6};

Answer 13

/* initial value of a is
 {1, 2, 3, 4, 5, 6, 0, 0, 0, 0} */

The remaining values become 0s

Question 14

What does this do?

int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

Answer 14

If an initializer is present, the length of the array may be omitted:

Question 15

In the case of no length given for an array, but an initializer is, what does the compiler do?

Answer 15

The compiler uses the length of the initializer

to determine how long the array is.

Question 16

In C, arrays are stored in what?

Answer 16

C stores arrays in row-major order, with row 0 first, then row 1, and so forth.
(sort of …. )

Question 17

What is the format of a 3-dimensional array and how are the elements accessed?

Answer 17

int b[2][3][4];
/* a 2 by 3 by 4 table */

2 layers
3 rows
4 columns

Question 18

Can an array be declared with an expression as the size?

int a[n=1];

Answer 18

Yes

Question 19

What is a string in C?

Answer 19

An array of characters ending with a special NULL character:

\0

Question 20

How do you declare a string in C?

Answer 20

char d[8] = “Magic”;

Question 21

What is the String library in C?

Answer 21

include string.h

Question 22

What does strlen return with regards to a string?

Answer 22

The length of a NULL terminated string

Question 23

What does
count = strlen(d);
return if d is “Magic”

Answer 23

5, even though there are 6 values (including the NULL character)

Question 24

What does strcpy do? Format?

Answer 24

It copies a character string into another string

source should be NULL terminated
destination should have enough room

strcpy(str2, str1);

Whatever was in str2 is replaced with whatever is in str1

Question 25

What does strcat do? Format?

Answer 25

Appends a copy of str2 to the end of str1

A pointer equal to str1 is returned

strcat(str1, str2);

Question 26

Can strings be compared using equality operators?

Answer 26

Yes

Question 27

What does strcmp do? Format?

What is returned if equal? If not equal?

Answer 27

Does an ASCII comparison one char at a time until a difference is found
between two chars in the same position.

int strcmp (str1, str2);

Returns 0 if equal
Returns anything BUT 0 if not equal

Note: spaces AND different capitalizations result in a false comparison

Ex:
DOG and DOG return 0
DOG and Dog return not 0
DOG and _Dog return not 0

Question 28

What does strchr do? Format?

What is returned if found? Not found?

Answer 28

strchr search str until ch is found or NULL character is found instead.
If found, a (non-NULL) pointer to ch is returned. Otherwise, NULL is returned instead.

char * strchr (char * str, int ch);

Question 29

The printf() function needs what when a variable is put in?

Answer 29

The type

Question 30

What are the following formatting labels?

%d
%u
%ld
%lu
%f
%lf
%c
%s

Answer 30

%d = signed integer
%u = unsigned integer
%ld = long signed integer
%lu = long unsigned integer
%f = float
%lf = double float
%c = character
%s = string

Question 31

What do the following mean?

\a
\b
\n
\t
\v
\\

Answer 31

\a = audible alert
\b = backspace
\n = newline
\t = tab
\v = vertical tab
\\ = backslash

Question 32

How do you print an integer with the following:

At least 5 wide

At least 5 wide, left-justified

At least 5 wide, zero-filled

At least 5 wide, with a plus-sign

At least 5 wide, plus sign, left-aligned?

Answer 32

At least 5 wide
printf(“‘%5d’”, 10);

At least 5 wide, left-justified
printf(“’%-5d’”, 10);

At least 5 wide, zero-filled
printf(“‘%05d’”, 10);

At least 5 wide, with a plus-sign
printf(“’%+5d’”, 10);

At least 5 wide, plus sign, left-aligned?
printf(“’%-+5d’”, 10);

Question 33

How do you print a float with the following formatting:

Print one position after the
decimal

Two positions after the decimal

Eight-wide, two positions after the decimal

Eight-wide, four positions after the decimal

Eight-wide, two positions after the decimal, zero-filled

Eight-wide, two positions after the decimal, left-justified

Printing a much larger number
with that same format

Answer 33

Print one position after the
decimal
printf("'%.1f'", 10.3456);

Two positions after the decimal
printf(“’%.2f’”, 10.3456);

Eight-wide, two positions after the decimal
printf(“‘%8.2f’”, 10.3456);

Eight-wide, four positions after the decimal
printf(“‘%8.4f’”, 10.3456);

Eight-wide, two positions after the decimal, zero-filled
printf(“‘%08.2f’”, 10.3456);

Eight-wide, two positions after the decimal, left-justified
printf(“’%-8.2f’”, 10.3456);

Printing a much larger number with that same format
printf(“’%-8.2f’“,101234567.3456);

Question 34

What is puts() ?

What is its formatting?

Answer 34

Another way of printing a string (simpler)

char sentence[] = “The quick brown fox”;
puts(sentence);

Question 35

How do you left-justify vs. right justify?

Answer 35

Right justify happens automatically, to left justify, you must append a dash “-“ like:

printf(“%-s”, string);

Question 36

What is the stdio.h function for taking in input? Format?

Answer 36

scanf(“%d”, &intVariableName);

Question 37

What do %s and %ns do in scanf()?

Answer 37

%s scans up to but not including the “next” white space character

%ns scans the next n characters or up to the next white space character,
whichever comes first

Question 38

What is the difference between scanf() and gets()

Answer 38

gets() reads in a line

scanf() can read in multiple lines

Question 39

Are ampersands included in formatting a scanf() for a character array?

Answer 39

No

scanf (“%s%s%s”, s1, s2, s3);
scanf (“%2s%2s%2s”, s1, s2, s3);