C

Question 1

Recall the basic structure of a C program

Answer 1

int main function

Question 1

How to make a comment in C

Answer 1

//

Question 2

What’s the formal name for fixed data (values) that we can use directly in a C program?

Answer 2

literals

Question 3

What are the data types in C (literals) - give examples

Answer 3

Basic data types (refer to image)

arrays
string (i.e. array of characters)

Question 4

How do we declare variables in C?

Answer 4

Depends on the data type of the variable we want to declare

(1) Integer Literals
int age;

(2) Floating-point Literals
double salary;

(3) Character Literals
char letter;

Question 5

How do we properly end a C statement?

Answer 5

Use semi-colon ;

Question 6

How do we print

Answer 6

printf(“”);

prints anything present inside the quotation marks

“%d”, age
prints anything present inside the quotation mark

Question 7

What is %d in this C statement?

printf(“%d”, age);

Answer 7

%d - format specifier for int data types
value of age replaces %d

Question 8

What are the respective format specifiers for each of the literal data types?

Answer 8

(1) Integer Literals
%d

(2) Floating-point Literals
%lf
(‘L’ f not 1)

(3) Character Literals
%c

Question 9

How do you print this:

Answer 9

Question 10

How many characters can the character variable store?

Answer 10

a single character inside single quotes

char letter = ‘s’;
NOT char letter = “s”;

Question 11

How do we change the value stored in a variable?
E.g. if we initially declare int age = 25 but want to change age to 35

Answer 11

age = 35;

Question 12

When we change a value stored in a variable, what should we note?

Answer 12

The new value must match the data type we initially declared for that variable.

Question 13

How do you name variables made up of 2 words?

Answer 13

camelCase

Question 14

Give some examples of illegal variable names

Answer 14

❌ spaces
❌ use of symbols (except alphabets, numbers and underscore)
❌ variable name starts with a number
❌ names already part of C syntax e.g. if, else etc

Question 15

How can we create multiple variables together in a single line?

Answer 15

Question 16

What do pointers allow us to do?

Answer 16

Work with memory addresses

Question 17

After creating and storing value in variable, how can we access the memory address of that value?

e.g.
int var = 13;

Answer 17

&var

Question 18

What is a pointer?

Use variable ‘pt’ as an example

Answer 18

a special symbol that stores the address of a variable rather than a value

int* pt;

Question 19

How can you assign an address to a Pointer?

Use int number = 36; as example

Answer 19

Question 20

Label the different parts of this C function

Answer 20

Question 21

What are some assignment operators?

Answer 21

=
+= (same as accumulator pattern in Python)
-=
*=
/=
%=

Question 22

How to limit the number of 0s when formatting floating points?

Answer 22

printf(“%.2lf”)

2 is the number of zeros we want to pad out the floating point with

Question 23

What result is returned when we use division operator on int and floating points?

e.g. 12 / 8
12.0 / 8.0

Answer 23

Integers - returns only the quotient (1)
Floating - returns exact result (1.50)

Question 24

What are the increment and decrement operators?

Answer 24

increment: ++ decrement: - -

Question 25

How would you use increment/decrement operators on say variable 'var'?

Answer 25

It is recommended in COMP9024 to put the operator after var var++ var--

Question 26

What data type can be used with increment and decrement operators?

Answer 26

only integers

Question 27

What is precedence and associativity?

Answer 27

Operators with higher precedence are executed first and operators with lower precedence are executed last (), * and / are calculated first before + and -

Question 28

How can we find out how much storage each data is occupying in the memory?

Answer 28

Use sizeof(variable) operator

Question 29

How do we print sizeof() calculations?

Answer 29

Use format specifier "%zu"

Question 30

What is the measurement does sizeof() return?

Answer 30

Bytes

Question 31

What kinds of type conversions are there?

Answer 31

(1) Implicit Type Conversion (2) Explicit Type Conversion - manually convert one type to another

Question 32

What happens if we try to assign a double value to an int variable? E.g. int number = 8; number = 35.48

Answer 32

We'll get only 35 Double values are larger (8 bytes) than integer values (4 bytes) so we'll lose data

Question 33

How do we manually convert one data type to another?

Answer 33

Question 34

What function allows us to take input from a user? How does it do that?

Answer 34

scanf() e.g. scanf("%d", &age); %d - format specifier that represents the type of input data &age - represents the memory address of the age variable The scanf() function takes int input (specified by %d) from the user and stores it in the memory location of the age variable.

Question 35

How can use booleans in our code in C?

Answer 35

import true and false using #include create boolean using bool

Question 36

In C, boolean values are represented in terms of which integer values?

Answer 36

true = any values except 0 false = 0

Question 37

What format specifier do we use to represent boolean value?

Answer 37

%d

Question 38

How do we write a boolean statement in C comparing int age = 25; Does age equal 25? Does age not equal 25?

Answer 38

Question 39

Name the 3 logical operators in C programming

Answer 39

&& - AND (age > 17) && (salary > 4000) || - OR (age > 17) || (salary > 4000) ! - NOT !(age > 17)

Question 40

How are if..else statements written in C?

Answer 40

Question 41

How are if..else if .. else statements executed in C?

Answer 41

Question 42

Create an array numbers containing integers 1, 2, 3, 4, 5

Answer 42

Question 43

How to access first element of this array? int numbers[5] = {1, 2, 3, 4, 5};

Answer 43

numbers[0]; or more generally, numbers[index]

Question 44

How do you write a switch statement?

Answer 44

Question 45

What does the while loop do?

Answer 45

repeat a block of code until the boolean expression of the loop is false

Question 46

What does the for loop do? Identify parts of a for loop

Answer 46

run a block of code for a certain number of times

Question 47

while vs for

Answer 47

Based on my experience with Python problems, it seems `while` loops are usually used to make an infinite loop and is best for a changing data source. We can specify when to break the loop and restart it from the top A `for` loop hardcodes conditions which is maybe more suited for an unchanging data source

Question 48

Can we omit an array size?

Answer 48

Yes, C will automatically keep track of it int array[] = {1, 2, 3, 4, 5};

Question 49

What happens if you assign Less Elements Than Size of the Array?

Answer 49

The remaining spaces will be filled with a random number

Question 50

What happens if we do this? declare array first then initialize all elements together after declaration

Answer 50

We're not allowed to do this

Question 51

How do we print something in C?

Answer 51

Question 52

What is the output of this print code?

Answer 52

The cube of 3 is 27. The first %d is for the arg1 the second %d is arg2

Question 53

How to code this output in C? Your "login ID" will be in the form of z1234567.

Answer 53

Question 54

recall how to write a do ... while loop

Answer 54

Question 55

do ... while vs while loop?

Answer 55

do ... while ensures the code body will be run before checking the condition while loop code body will only run if the condition is true

Question 56

what metaphor can we relate the `while` and `do ... while` loop to?

Answer 56

Fixing equipment I fix equipment, then check whether it's actually fixed. If it's not fixed, I continue fixing While Is this device safe to use? If a tool is safe to use I continue using it

Question 57

return-type functionName(void) { // code block } what does void in the argument mean?

Answer 57

function has no arguments

Question 58

float vs double data types

Answer 58

float is a lower precision decimal number (less number of digits to the right of the decimal place), double is precise

Question 59

what is this called (at the beginning of a C program)?

Answer 59

symbolic constant

Question 60

what is a symbolic constant

Answer 60

typically defined at the top of a C program where the variable (`MAX`) is followed by associated value (`20`)

Question 61

what happens when the symbolic constant is read by the compiler's pre-processor?

Answer 61

all occurrences of variable is replaced by associated value

Question 62

when will the symbolic constant NOT be replaced?

Answer 62

(1) occurs inside string (2) as part of another name

Question 63

when would it be useful to use symbolic constants

Answer 63

- avoid burying "magic numbers" in the code (slide 58) - make the code easier to understand and maintain (slide 57)

Question 64

what styles would be useful in COMP9024

Answer 64

Style considerations that do matter for your COMP9024 assignments: * consistent indentation (3 spaces throughout, or 4 spaces throughout, do not use TABs) * keep functions short and break into sub-functions as required * use meaningful names (for variables, functions etc) * use symbolic constants to avoid burying "magic numbers" in the code * comment your code "as much as possible"

Question 65

how many spaces would the string "hello" take up in memory? why?

Answer 65

6 because the last character is the end of string delimiter \0

Question 66

what are 2 different ways we can initialise a string array?

Answer 66

Question 67

how do we use the construct atoi()?

Answer 67

say it as "a to i" #include n = atoi(str)

Question 68

what does atoi() do?

Answer 68

converts string to integer to use in computation

Question 69

what does typedef do?

Answer 69

allows us to give meaningful names to data types

Question 70

what are 2 ways to initialise multi-dimensional arrays?

Answer 70

Question 71

What is a structure in C?

Answer 71

collection of variables (can be of different types) under a single name

Question 72

how do we define a structure?

Answer 72

use struct

Question 73

How do we access components of the structure?

Answer 73

Using dot operator Person.name

Question 74

When we defining a structured data type, is any memory allocated?

Answer 74

No

Question 75

After we've defined a structured data type, how do we allocate memory?

Answer 75

Declare a variable

Question 76

How can we use a structure that's passed as a parameter to a function? E.g. a function that prints the date using DateT structure

Answer 76

Question 77

When we define a struct, we are basically creating a ___

Answer 77

data type like double and int

Question 78

What are two ways we can create struct variables?

Answer 78

Question 79

Is this valid code to create struct variables? Why/why not?

Answer 79

With `typedef` keyword, `person1` and `person2` become aliases instead of struct variables

Question 80

How can you create struct variables using typedef

Answer 80

Question 81

What does typedef do?

Answer 81

Creates an alias name for struct

Question 82

Why do we use structs?

Answer 82

if we have to store multiple attributes of related data, structs make our code easier to write and understand, improves readability