CS50 Week 2

Question 1

How many bits is an int?

Answer 1

32

Question 2

How many bits is a long long

Answer 2

64

Question 3

How many bits is a float?

Answer 3

32

Question 4

How many bits is a double?

Answer 4

64

Question 5

How many bits is a char?

Answer 5

8

Question 6

Reminder: variables declared inside curly braces have scope limited to within the curly braces.

Answer 6

Reminder: variables declared inside curly braces have scope limited to within the curly braces.

Question 7

How do you declare a global variable?

Answer 7

Declare it before main()

Question 8

What is the function that gives a string’s length, and where is it found?

Answer 8

strlen(string)

string.h

Question 9

How is a variable declared?

Answer 9

type name(parameter)

Type is the data type that will be returned

Question 10

What is the type of a function that returns no value?

Answer 10

void

Question 11

Where is a function declared?

Answer 11

The name should be declared above main()

The actual body of the function should be declared after main()

Question 12

How many numbers can be represented by a 32 bit int?

Answer 12

2^32

roughly four billion

Question 13

How do you cast numbers into a type while in an equation?

Answer 13

(float) 1

(float) #

Question 14

Why can we convert between chars and ints?

Answer 14

Because chars are actually number values that correspond to symbols per ASCII

Question 15

What is one thing that marks the limit of scope in C?

Answer 15

Curly braces.

Any variable declared inside a set of curly braces does not exist outside the curly braces.

Question 16

How is a global variable declared in C?

Answer 16

It is declared before the main() function.

Question 17

Why can you access an individual character within a string?

Answer 17

Because strings are implemented in the CS50 library are actually arrays of chars.

Question 18

How do you access a certain element of a string?

Answer 18

stringName[i]; where i is the index of the character you want to access.

Counting starts at 0.

Question 19

Where is a user made function declared?

Answer 19

Above main(), if it will be used in main().

Question 20

What is the sentinel value that GetString() returns when the function fails to get a string?

Answer 20

NULL

Question 21

How do you declare multiple variables in one line?

Answer 21

int a = 0, b = 1 …

Question 22

What C library contains functions that classify and transform individual characters?

Answer 22

ctype.h

Question 23

When are curly braces not needed for if-else blocks?

Answer 23

When the following code is only one line.

Question 24

How do you access the man pages?

Answer 24

type “man functionName”

Question 25

What is the physical representation of the NUL character?

Answer 25

\0

Question 26

What is the primary purpose of an array?

Answer 26

To store multiple instances of a data type in one place.

Question 27

How do you declare an array?

Answer 27

i[#]

where # is the number of elements in the array.

Question 28

How are command line arguments established, according to convention?

Answer 28

int main(int argc, string argv[])

Question 29

What is argc?

Answer 29

Argument count

It is an int describing the number of arguments passed to main(). The name of the program counts as one argument.

Question 30

What is argv[]?

Answer 30

An array of the arguments themselves.

The first element (the 0th element) is always the name of the program.

Question 31

What is argv[] in actuality, given the nature of strings?

Answer 31

Because a string is an array of characters, argv[] is an array of arrays.

Question 32

How would you access a certain character in a command line argument?

Answer 32

argv[i][n]

where i is the string you are trying to access, and n is the individual char within the string.