C

Question 1

include

Answer 1

Library then add name

Question 2

int main (void)
{
}

Answer 2

beginning of program

Question 3

get_string()

Answer 3

• ask for a string

Question 4

printf()

Answer 4

print string

Question 5

printf(“hello,%s\n”, answer)

Answer 5

print variable

Question 6

%c

Answer 6

char placeholder

Question 7

%f

Answer 7

float, double placeholder

Question 8

%i

Answer 8

int placeholder

Question 9

%li

Answer 9

long placeholder

Question 10

%s

Answer 10

string placeholder

Question 11

\n

Answer 11

new line

Question 12

return-type name (argument_list)

Answer 12

• make a new function
• function is referred to on top, but body is below code
• first void is type of output
• second void is type of input
• when a function has no arguments it is void

int add_two_ints (int a, int b); \function declaration

int main (void)
{
int x = 8;
int y = 9;

printf(“%i”, add_two_ints(x,y));

}

int add_two_ints (int a, int b)
{
return a + b;
}

Question 13

int

Answer 13

• 4 bytes (32 bit)

~- 2 bill to ~+2 bill

Question 14

unsigned int

Answer 14

• no negatives

- 2x positive number ~+4 bill

Question 15

chars

Answer 15

• store single characters
• 1 byte (8 bits)
• 0 to 127

Question 16

float

Answer 16

• real numbers (decimal)
• 4 byte (32 bits)
• precision problem

Question 17

double

Answer 17

• real numbers (decimal)
• 8 byte (64 bits)
  more precise

Question 18

void

Answer 18

• type, not datatype
• function with void does not return value
• parameter with void does not take parameter
• placeholder meaning ‘nothing’

Question 19

bool

Answer 19

• include library cs50
• boolean value
• true or false

Question 20

create variable [type] [name]

Answer 20

int number;
char letter;
int height, width;

Question 21

initializing

Answer 21

int number = 17;

char letter = “15”;

Question 22

Operators

Answer 22

• +, -, /, *, %

- % remainder

Question 23

x *= 5

Answer 23

x = x *5

Question 24

x++

Answer 24

increment by 1

Question 25

x–

Answer 25

decrease by 1

Question 26

&&

Answer 26

• and

- only if both operand are true

Question 27

||

Answer 27

• or

- only if operand or both are true

Question 28

!

Answer 28

• not
• inverts the value of the operand
• true becomes false

Question 29

==

Answer 29

• equals to

Question 30

!=

Answer 30

• not equal to

Question 31

IF

Answer 31

if (boolean)
{
}

• if boolean true executes {}
• false will not execute

Question 32

IF ELSE

Answer 32

if (boolean)
{
}
else
{
}

• if true will execute first {}
• if false will execute else

Question 33

ELSE IF

Answer 33

if (boolean)
{
}
else if (boolean_2)
{
}
else if (boolean_3)
{
}
else
{
}
- mutually exclusive branches

Question 34

SWITCH

Answer 34

int x = GetInt();
switch(x)
{
case 1:
printf("one!\n");
break;
case 2:
printf("two!\n");
break;
case 3:
printf("three!\n");
break;
}

• specific cases
• have to put break between if you want to stop
• if no break, it will fall through

Question 35

? :

Answer 35

int x;
if(bool_exp)
{
x=5
}
else
{
x=6
}

instead can write

int x = (bool_exp) ?5:6;

• This is a short conditional branch
• Use only for simple branches

Question 36

WHILE

Answer 36

while (true)
{
}

• Infinite loop

Question 37

WHILE (bool_expr)

Answer 37

while (bool_expr)
{
}

• repeat until bool_expr becomes false

Question 38

DO WHILE

Answer 38

do
{
}
while (bool_expr)

• execute until bool_expr false
• will run at least one time
• unknown # of times will run, but at least once

Question 39

FOR

Answer 39

for (start; expr; increment)
{
}

ex.
for (int i = 0; i < 0, i++)
{
}

• do loop a certain number of times
  1. start - set counter
  2. expr - bool_expr (if true, execute loop)
  3. increment - increase/decrease counter

Question 40

Compiling

Answer 40

• preprocessing: get relevant code from the library to be used in code
• compiling: turns it into assembly code
• assembling: converts assembly to binary
• linking: brings different files together

Question 41

Casting

Answer 41

Converts one data type to another

• char c1 = ‘H’;
• printf(“%i”, (int) c1);
  72

Question 42

get_int()

Answer 42

get integar

Question 43

include string.h

Answer 43

string library

Question 44

strlens()

Answer 44

string length

Question 45

Array

Answer 45

• it is a data structure
• must be the same type
• each block is an element
• access by index #
• index starts at 0 and last is n-1 (ex. 50 elements, 1st: 0, last: 49)

Question 46

type name[size];

int student_grades[40];
double menu_prices[8];

Answer 46

• type: variable (int char, etc.)
• name: what you are calling it
• size: how many elements

Question 47

type name[size] = {}

int student_grades[4] = {92, 78, 36, 80};
or
int student_grades[] = {92, 78, 36, 80};

Answer 47

• fill an array

- do not need to declare the number before declaration

Question 48

type name[size][index]

bool battleship[10][10]

Answer 48

• 10 by 10 grid

Question 49

Copying an array from one variable to another variable

Answer 49

int foo[5]
int bar[5]

for(int j = 0; j < 5; j++)
{
bar[j] = foo[j];
}

DO NOT bar = foo because it does not copy in C

Question 50

int main(int argc, string argv[])
{
}

Answer 50

• collect data at the command line
• argc: argument count
  1. how man arguments the user typed (ex. ./greed is 1 argument, and ./greedy 1024 cs50 is 3 arguments)
• argv: argument vector
  1. stores strings only, one string per element (ex. ./greedy 1024 cs 50 has 3 strings [0] “./greedy” [1] “1024” [2] “cs50”

Question 51

Local Variable

Answer 51

• can only be accessed within the function (including main)
• passed by variable (1) callee recieves a copy of the variable, not the variable itself (2) variable in the caller remains unchanged unless overwritten

Question 52

Global Variables

Answer 52

• can be accessed by any function in the program

- declare it outside of all functions

Question 53

Recursion

Answer 53

Function that calls it self

factorial(n!)

fact(n) = n * fact(n-1)

Question 54

TypeDef

Answer 54

Create your own data structure

typedef struct
{
string name;
string number;
}
person; //name of typedef

int main (void)
{

person people[4]; //type and name of array

people[0].name = "EMMA";
people[0].number = "928930";
people[1].name = "Brian";
people[1].number = "23948939";

}