Cs50

Question 1

Cs50 library

Answer 1

Include < Cs50.h>

Question 2

General C library

Answer 2

include

standard io(input/outputs functions)

Question 3

Int
What is it?
How many bytes /bits of memory?

Answer 3

C data type/variable;
Used for variables that will store
4 Bytes/32 bits
Range from -2^31 to 2^31 minus 1 because we need as spot for 0

Question 4

How can you double the value that an integer or other data type can take on?

Answer 4

Use “unsigned” qualifier;
Ex.) unsigned int → useful when you need a larger range and don’t need negative numbers;

Rangefor unsigned int = 0 to 2^32-1

Question 5

Char

Answer 5

1 byte 18 bits; a single character;
Range from -2^7 to 2^7-1 (-128 to 127)
ASCII has single characters, or chars, mapped to numbers
Ex A =65; a=97

Question 6

Floating point numbers (float)

Answer 6

Real numbers with decimals.floats have a precision problem because with only 32 bits

Question 7

Double

Answer 7

Data type like a float but fit 8 bytes so double precision

Question 8

What is type, but not a data type?

Answer 8

void
Can’t create a data type of “void” and assign a value to it
But it can be a return type in a function.
Printf→ doesn’t return a value

Question 9

Bool

Answer 9

data type;only capable of 2 values true or false.

In C, every non-0 number is true, 0 is false

Question 10

String

Answer 10

data type;

Text→ vanables that will store a series of characters (words,sentences, paragraphs, etc.)

Question 11

Struts/typedefs

Answer 11

Structures and defined types

Question 12

What 2 things do you need to create a variable?

Answer 12

① give it a type
② give it a name

int number;
char letter;

Question 13

How do you create multiple variables at once for a given type?

Answer 13

int height, width;

float sqrt2,sqrt3, pi;

Question 14

Initialization

Answer 14

When you declare a variable and assign it @ the same time.

int number =17;

Question 15

Arithmetic operators

Answer 15

Add +
Subtract -
Multiply *
Divide /

Question 16

Modulus operator %

Answer 16

Gives us the remainder
Ex. int m= 13 % 4 // m is now 1

Random number generator →

Question 17

Equivalent syntax for

x = x * 5;

Answer 17

X *= 5;

Question 18

X++;

X–;

Answer 18

Increase or decrease variable by 1

Question 19

Logical operator

Answer 19

AND (&&)
x && y ;

Boolean expression where both operands are true, otherwise false;

OR (| |)
True if and only it @ least one of the operands is true
x || y
X can be true, Y can be true, X and y can be true, but both can’t be false

NOT (!) → inverts value of its operand, also called bang
If x is true, !x is false
If x is false, !x is true

Question 20

Relational operators

Answer 20

x < y
X <= y
X > y
X >= y
X == y equal
X !=y not equal

Question 21

Conditional expressions

if else

Answer 21

If (boolean-expression)
{

}
else (boolean-expression)
{

}

Question 22

How can you write a simple if else conditional on one line?

Answer 22

int x = (expr) ? 5 : 6;

Here, if expression is true, assign value of 5, else assign it a value of 6

Question 23

Switch conditional

Answer 23

Use discrete cases to make decisions

Question 24

While Loops

Answer 24

While (true)
{

}

This is a forever loop.

While (boolean-expression)
{

}

Question 25

Do while loops

Answer 25

do
{

}
While (boolean-expression);
Do-white is guaranteed to run @ least once.

Question 26

For loop

Answer 26

Used to repeat something a specific number of times

for (int i = ; i < 10; i++)

Question 27

Linux command line

Answer 27

ls → list
cd→ change directory
pwd → present working directory
mkdir → make directory
cp   → copy from a source to a destination
rm 
mv   → mv from a source to a destination