Week 3: Compiler Directives, Data types, and Binary Representation

Question 1

What is cpp?

Answer 1

C preprocessor

Question 2

What does the preprocessor do?

Answer 2

Creates a “new” version of your
program and it is this new program that actually gets
compiled

Question 3

What is the format of the substitution Macro and what does it do?

Answer 3

define text1 text2

Tells the compiler to find all occurrences of “text1” in the source code and substitute “text2”.

Question 4

What does the #undef … directive do?

Answer 4

Makes sure that defined(…) evaluates to false

Question 5

What is the format of the include directive?

Answer 5

include

Question 6

what does inline do?

Answer 6

When the compiler compiles your program, it will not compile it as a function. Rather, it just integrates the necessary code:
ex:

inline int max(int a, int b) {
return a>b?a:b;
}

Question 7

Can inline function improve the speed of your program?

Answer 7

Yes

Question 8

Where are inline functions often defined?

Answer 8

In header (.h) files

Question 9

What is the main difference between a #define statement and a function call if they look similar?

Answer 9

define will run until completion until every variable is incremented (even post incrementation like “i++”)

A function call of similar type will return before the post incrementation

Question 10

How many bits is UTF-8? UTF-16? UTF-32?

Answer 10

8-bits, 16-bits, and 32-bits respectively

Question 11

What does A start at in UTF-8? a?

Answer 11

A: 0100 0001
a: 0110 0001

Question 12

What is 1s complement form?

Answer 12

Every negative number is simply the positive number with EVERY single digit flipped

Question 13

All whole number integers are stored in either?

Answer 13

Magnitude only or 2s complement

Question 14

How many bytes does a character take?

Answer 14

1 byte

Question 15

How many bytes does a short take?

Answer 15

2 bytes

Question 16

How many bytes does an int take?

Answer 16

4 bytes

Question 17

How many bytes does a float take?

Answer 17

4 bytes

Question 18

How many bytes does a double take?

Answer 18

8 bytes

Question 19

What is a quad word?

Answer 19

8 bytes / 64 bits

Question 20

What is the format of a character declaration / initialization

Answer 20

char a;
a = ‘g’;

OR

char a = ‘g’;

NOTE: single quotes

Question 21

For a computer to perform an arithmetic operation, the operands must be

Answer 21

The same size (number of bits) and the same type

Question 22

In C, if a variable must be converted to another type, what is the preference?

Answer 22

The computer will always convert to the more complex representation (variable promotion)

Question 23

What is variable promotion?

Answer 23

Promoting to the more complex representation

Question 24

What is implicit conversion?

Answer 24

When data types are upgraded to become the same type (the largest) automatically

Question 25

What is explicit conversion?

Answer 25

The programmer forcing an expression to be of a specific type (type casting)

Question 26

What is type casting?

Answer 26

The programmer forcing an expression to be of a specific type

Question 27

What is the format of type casting?

Answer 27

(data_type)(expression); Example: (int)x + 1;

Question 28

Can type casting force a higher data type to a lower data type?

Answer 28

Yes

Question 29

What are the two ways of making a boolean MACRO?

Answer 29

``` #define BOOL int and typedef int BOOL; ```

Question 30

What does typedef do? Syntax?

Answer 30

Creates an alias for a type typedef (known data type) (alias to be used instead of)

Question 31

What is the difference between the following? #define max(a,b) ( (a) > (b) ? (a) : (b) ) #define max(a,b) a>b?a:b

Answer 31

``` #define max(a,b) ( (a) > (b) ? (a) : (b) ) is seen as: printf("%d", 2 * ( (3+3) > (7) ? (3+3) : (7) ); ``` ``` #define max(a,b) a>b?a:b is see as: printf("%d", 2 * 3+3 > 7 ? 3+3 : 7 ); ```

Question 32

``` If there is a macro directive like so: #define max(x,y) ((x)>(y)?(x):(y)) ``` What does the preprocessor see with the following input: n= max( i++, j);

Answer 32

/* Same as n= (( i++ )>( j )?( i++ ):( j )) */