C Programming

Question 1

Does C have keywords?

Answer 1

Yes but it only has 32 unlike other languages that have hundreds.

Question 2

How does C identify what is a function?

Answer 2

If a line of code follows the format:
functionReturnType FunctionIdentifier (argument) {}
C will recongnise it as a function e.g:
int main (void) {
do_this;
}

Question 3

What command would you use to compile a C program called hey.c to hello.exe?

Answer 3

gcc hello.c -o hello.exe

Question 4

Why does C need stdio.h?

Answer 4

stdio.h is the library for all the standard input and output functions in C. Without it the program cannot receive input or display output.

Question 5

What command would you use to run a program called hello.exe?

Answer 5

You would navigate to it’s directory in Cygwin and use:

./hello.exe

Question 6

How would you declare a constant long float variable called pi with the value 3.1415926535?

Answer 6

const long float pi = 3.1415926535;

Question 7

With the variables:
int age = 27;
char bang = !;
How would you print the statement:
"I am going to be 27 years old this year!"

Answer 7

The command you would use is:

printf(“I am going to be %d years old this year%c”, age, bang);

Question 8

What are the format specifiers of:
int:
char:
float:
double:
string:

Answer 8

int: %d
char: %c
float: %f
double: %lf
string: %s

Question 9

Fill out the table of bitwise operators for the following:
P   Q     P&Q   P|Q   P^Q
0   0
0   1
1    1
1    0

Answer 9

P   Q  
0   0    
0   1         
1    1                     
1    0   

P&Q
0
0
1
0

P|Q
0
1
1
1

P^Q
0
1
0
1

Question 10

How would you receive an integer input and store it in a variable called age?

Answer 10

int age;

scanf(%d, &age);

Question 11

Use the binary sequence x = 0100 0110 for the following and calculate the new binary value:
x &laquo_space;2;
x&raquo_space; 2;

Answer 11

x = 0100 0110
x &laquo_space;2 = 0001 1000
x&raquo_space; 2 = 0001 0001

Question 12

Write an if statement that prints out a users tax percentage based on the 2021 ATO standards and their income.

Answer 12

int income;

if(income < 18200)
{
  printf("You don't have to pay tax!");
}
else if(income >= 18200 && income < 45000)
{
 printf("You pay 19% tax");
}
else if(income >= 45000 && income < 120000)
{
 printf("You pay 32.5% tax");
}
else if(income >= 120000 && income < 180000)
{
 printf("You pay 37% tax");
}
else
{
 printf("You pay 45% tax");
}

Question 13

C doesn’t have booleans as a data type. How do we get around this?

Answer 13

We can define true and false at the start of the code.
E.g
#define TRUE 1
#define FALSE 0

Question 14

What are 4 things all switch statements need?

Answer 14

1. A controlling expression e.g switch(job)
2. A case label e.g case ‘Carer’:
3. Statements e.g do_this;
4. A break keyword e.g break;

All together:

switch(job){

case ‘Carer’ :
{_do_this;}
break;

case ‘Boxer’:
{_do_that;}
break;

Question 15

What would we use to find the address of the first byte of int variable t?

Answer 15

int t;

&t;

Question 16

What is *y showing us?

Answer 16

*y is returning the address of the variable y. * denotes that the variable is a pointer. Pointers ‘point’ to the address of the variable that follows.

Question 17

Are while loops always executed?

Answer 17

No. A while loop has the controlling statement evaluated first so there are instances where the statement in the loop may never be triggered.

Question 18

What happens if we put a switch statement within a while loop and a break occurs?

Answer 18

The break will only break out of the switch not the while loop. Break statements only break out of the brackets to one level up.

Question 19

Write a for loop that prints out the numbers 2,…..,40 in multiples of 2.

Answer 19

for(i = 2, i <=40, i+= 2)
{
printf(“%d”, i);
}

Question 20

How and why would you write an inifinite loop?

Answer 20

while(1)

An we might use an infinite loop to read input to a program.

Question 21

Why would we use a do loop over a while loop?

Answer 21

do loops check the controlling statement after executing one time. Therefore they are useful if a code needs to be executed at least once, such as to initialise values. If you use a while loop the code can sometimes never be executed.

Question 22

Write a for loop that prints every number from 1 to 15.

Answer 22

while(int i = 1, i <=15, i++)

{ printf(“%d”, i); }

Question 23

What is the difference between break and continue?

Answer 23

break exits a loop.

continue skips the code that follows and goes back to the start of the loop

Question 24

What are the three datastreams?

Answer 24

STDIN (0) - data into program
STDOUT (1) - data out of program
STDERR (2) - standard error message

Question 25

How can we add the word ‘dog’ to the end of a text file called ‘pets.txt’?

Answer 25

We would use redirection:

dog&raquo_space; pets.txt

Question 26

What is piping and why is it useful?

Answer 26

Piping allows us to feed data from one program into another using the ‘|’ symbol. It is useful for getting two programs to interact. We use format:
program1.exe | program2.exe

Question 27

Where do we define a function?

Answer 27

Define a function after the main() call.

Question 28

Where do we call a function?

Answer 28

Functions are usually called in the main.

Question 29

Does passing an argument by value change it’s value? Why/Why not?

Answer 29

Passing an argument by value doesn’t change the variables value. It only creates a local copy and changes that.

Passing an argument by reference includes it’s address so the function can reach the variable and change it’s value.

Question 30

What is the difference between local and global variables?

Answer 30

Local variables

• Declared in the body of a function.
• Not visible outside the function
• Only exist during function execution.

Global variables

• Declared outside function bodies.
• Visible to all functions in the file.
• Allocated storage for the whole duration of the program.