1. Fundamental Programming
More Basics
Fundamental Programming

2. What’s Next
we started out with a minimal level of C++ syntax to get you started
Next four sessions:
Back to Basics – more basic C++
Testing – what is testing, and how do you do it?
More on Selection – everything you always wanted to know about if…else…
More on Repetition – different looping constructs
Fundamental Programming

3. #include <iostream.h>
a couple of comments about this…
# lines are not compiled, they simply direct the actions of the compiler – compiler directives , we’ll meet more later…
all standards libraries are enclosed in angle brackets , libraries you develop are enclosed in double-quotes - later you’ll learn how to do this
Fundamental Programming

4. void main (void)
the second void above means that main has no input of output variables; actually, it is optional – you will sometimes see:
void main()
also, you will sometimes see int before main – a main function that returns an integer
int main()
{... return ErrorNumber; }
this is used to return an error number to the operating system – 0 means no error
Fundamental Programming

5. Data Objects
Study Guide uses the term data object to refer collectively to variables and constants
variable : holds a value that will vary
constant : holds a value that is constant – cannot be changed in the program
const int
BOILING_POINT_OF_WATER = 100;
const float
ABSOLUTE_ZERO = ;
declared like variables, with const before data type
Fundamental Programming

6. Naming Rules start with a letter: A-to-Z, a-to-z
can contain upper or lower case letters, numerals (0-to-9), or underscore
only first 32 characters are significant
some compilers will allow you to use more
compiler may not be able to distinguish between different names with same first 32 characters
so, good idea to limit to 32 characters
avoid reserved words like int, float, etc
Fundamental Programming

7. Style Guide many organisations use a style guide
the goal is consistency in program code – to make it easier to maintain
we use a simple Style Guide in this course:
all names (functions, variable and constants) start with upper case letter
variables use mixed case – capitalise first letter of each word: StudentMark
constants are all upper case – use underscore to separate each word: ABSOLUTE_ZERO
for details see: Study Guide (p. 7-19)
Fundamental Programming

8. Local Data Objects
local data objects: local to the function where they are declared; not visible outside the function
objects declared
in a function are local
- are not visible outside function
#include <iostream.h>
void main (void) {
const float
ABSOLUTE_ZERO = ;
int
Temperature = 0; : }
Fundamental Programming

9. Global Data Objects
global data objects: declared outside functions - before main; visible everywhere
#include <iostream.h>
const float
ABSOLUTE_ZERO = ;
void main (void) { : }
objects declared
before main are global - visible everywhere
global variables are not recommended in this course – but may be used for now!
Fundamental Programming

10. Data Types
the choice of data type affects how much memory is used to store a value, and what you can store…
short int uses 2 bytes of memory (16 bits) and can hold a maximum value of 32,767
long int uses 4 bytes of memory and can hold a maximum value of 2,147,483,648
float uses 4 bytes and can hold a maximum value of 3.4 * 1038
double uses 8 bytes and holds a maximum value of 1.7 * 10308
Fundamental Programming

11. Data Types
the choice of real type also affects the precision of numbers you can store – the number of significant digits
float provides 7 significant digits –
is stored as
1,234,567,890 is stored as 1,234,568,000
double provides 15 significant digits
see: Study Guide (p. 7-12); textbook (p41)
Fundamental Programming

12. Data Type Demotion
when you assign a real value to an integer variable, we say that it is demoted – try:
int IntVariable;
IntVariable = 3.7;
cout << IntVariable;
the above code will output the value 3
the value 3.7 is demoted to 3 when it is assigned to an integer variable - the .7 is truncated (chopped off)
Fundamental Programming

13. Data Type Promotion
when you assign an integer value to a real variable, we say that it is promoted
nothing to worry about here - no data is lost…
int IntVariable = 3;
float FloatVariable;
FloatVariable = IntVariable;
no information lost!
Fundamental Programming

14. Expressions watch out for this one – try this:
int IntVariable1 = 3,
IntVariable2 = 4;
cout << IntVariable1 / IntVariable2;
this code will output 0 – both operands are integers, so an integer result is given
you can fix this by converting one of the operands to a real type:
cout << float(IntVariable1) / InVariable2; or
cout << 1.0 * IntVariable1 / InVariable2;
Fundamental Programming

15. Expressions one more thing about expressions – try:
cout << 2 + (Variable = 3);
you might expected this to cause a compilation error – it doesn’t, it outputs 5
in C++, an assignment is considered to evaluate to the value being assigned
this is why the compiler does not object to:
if (Variable = 3) :
take care to avoid this type of error
Fundamental Programming

16. Activity what will the following program output?
#include <iostream.h>
void main(void) {
int Variable;
if (Variable = 2)
cout << “True”; }
else
cout << “False”;
Fundamental Programming

17. Activity Break
Fundamental Programming

18. Activity Feedback the program will output: “True”
#include <iostream.h>
void main(void) {
int Variable;
if (Variable = 2)
cout << “True”; }
else
cout << “False”;
as the expression does not evaluate to 0 (it evaluates to 2), it’s True
Fundamental Programming

19. ASCII Coding System ASCII coding system is used to encode text:
) is stored as 41
1 is stored as 49
A is stored as 65
a is stored as 97
some values in ASCII coding system were reserved for controlling output devices
7 sound a beep - Bell
10 move to next line – Line Feed
13 move to start of current line – Carriage Return
for details see: Study Guide (p. 7-13)
Fundamental Programming

20. Special Characters
the backslash character is used to send special characters to cout:
\a - Bell
\r – Carriage Return
\n – Line Feed
\t – Horizontal Tab
example:
cout << “\t\tInvalid Input!\a\n\n“;
if you want to output the string “\t”:
cout << “\\t“;
for details see: Study Guide (p. 7-25)
Fundamental Programming

21. More On cin
one feature of cin is that it can read multiple input values off a single input line :
Sum = 0;
while (InputValue != -1) {
Sum = Sum + InputValue;
cin >> InputValue; }
cout << “Sum = “ << Sum;
when extracting a value from cin, characters are read from the keyboard until it reaches a white space character – space or new-line 1 2 3 4 -1
Sum = 10
Sum = 10
Fundamental Programming

22. More On cin
sometimes you may want to throw away all characters to the end of the input line :
char Char = ' ';
while (Char != 'X') {
cout << "Enter X to exit ==> ";
cin >> Char; }
Enter X to exit ==> abcdef
Enter X to exit ==> Enter X to exit ==>
Fundamental Programming

23. More On cin
to ignore all characters to the end of the input line, do this: :
char Char = ' ';
while (Char != 'X') {
cout << "Enter X to exit ==> ";
cin >> Char;
cin.ignore(80,’\n’); }
ignore up to 80 characters, or to end-of-line
Enter X to exit ==> abcdef
Enter X to exit ==>
Fundamental Programming

24. More On cin
or this… :
char Char = ' ‘,
OtherChar;
while (Char != 'X') {
cout << "Enter X to exit ==> ";
cin >> Char;
OtherChar = ‘ ‘;
while (OtherChar != '\n')
cin.get(OtherChar); }
get characters from keyboard until we reach end-of-line
Enter X to exit ==> abcdef
Enter X to exit ==>
Fundamental Programming

25. More On cin
as mentioned previously, we do not want to waste too much time on cin
in this course, your programs are not required to handle input data of the wrong type – if an integer is required, you can assume the user will enter an integer
for more details see: Study Guide (p )
Fundamental Programming

26. More On cout
using cout, you can output more than one expression in a single statement
cout << “Var1 = “ << Var1 << endl;
often we want to format output, like:
the iomanip library has some functions that are useful for formatting output…
Centigrade Fahrenheit
========== ==========
Fundamental Programming

27. set number of significant digits for all following output values
#include <iostream.h>
#include <iomanip.h>
void main(void) {
cout << << endl;
cout << setprecision(5);
cout << setw(8); }
set number of significant digits for all following output values
set column width for next output value
1.2346
Fundamental Programming

28. Activity what output will this program produce?
#include <iostream.h>
#include <iomanip.h>
void main(void) {
cout << "Centigrade Fahrenheit\n";
cout << "========== ==========\n";
cout << setw(10) << 100 << 212 << endl;
cout << setprecision(5);
cout << setw(10) << << << endl;
cout << setprecision(3);
cout << setw(10) << << << endl;
cout << setw(10) << << << endl; }
Fundamental Programming

29. Activity Break
Fundamental Programming

30. #include <iostream.h>
#include <iomanip.h>
void main(void) {
cout << "Centigrade Fahrenheit\n";
cout << "========== ==========\n";
cout << setw(10) << 100 << 212 << endl;
cout << setprecision(5);
cout << setw(10) << << << endl;
cout << setprecision(3);
cout << setw(10) << << << endl;
cout << setw(10) << << << endl; }
Activity Feedback
Centigrade Fahrenheit
========== ==========
100212
1.23e e+06
scientific notation used here because only 3 significant digits are output
Fundamental Programming

31. Activity Feedback if we, set number of significant digits to 9
#include <iostream.h>
#include <iomanip.h>
void main(void) {
cout << "Centigrade Fahrenheit\n";
cout << "========== ==========\n";
cout << setprecision(9);
cout << setw(10) << 100
<< setw(11) << 212 << endl;
cout << setw(10) <<
<< setw(11) << << endl;
cout << setw(10) <<
<< setw(11) << << endl;
cout << setw(10) <<
<< setw(11) << }
Activity Feedback
if we, set number of significant digits to 9
Centigrade Fahrenheit
========== ==========
and set width of second column to 11, we get
Fundamental Programming

32. More On cout
setprecision only applies to floating point numbers – it has no effect on integer output
cout << setprecision(2);
cout << 1000;
scientific notation is used when the number of digits preceding decimal place exceeds the number of significant digits to output
cout << 100.0;
1000
1.e+02
Fundamental Programming

33. More On Assignment Pascal has only one assignment operator:
<variable> := <expression>;
C++ has a number of assignment operators – the two statements below are equivalent:
NbrMarks = NbrMarks + 1;
NbrMarks += 1;
as are the two below:
Remainder = Remainder - CandidateFactor;
Remainder -= CandidateFactor;
for more see: Textbook (p. 169)
Fundamental Programming

34. Comments two types of comments – single-line, multi-line
// This is a single-line comment, each line of
// the comment must start with //
/* This is a multi-line comment – the comment
runs for any number of lines until we reach */
recommendation: use single-line comments –then, multi-line comments can be used to comment-out lines of code :
cout << “Variable1 = “ << Variable1;
// display value of other variables
cout << “Variable2 = “ << Variable2;
Fundamental Programming

35. Comments two types of comments – single-line, multi-line
// This is a single-line comment, each line of
// the comment must start with //
/* This is a multi-line comment – the comment
runs for any number of lines until we reach */
recommendation: use single-line comments – then multi-line comments can be used to comment-out lines of code :
/* cout << “Variable1 = “ << Variable1;
// display value of other variables
cout << “Variable2 = “ << Variable2; */
Fundamental Programming

36. Activity would this not work if we had: :
cout << “Variable1 = “ << Variable1;
/* display value of other variables */
cout << “Variable2 = “ << Variable2;
what would be the effect of
adding /* here
and adding */ here
Fundamental Programming

37. Activity Break
Fundamental Programming

38. Activity Feedback why would this not work if we had:
/* cout << “Variable1 = “ << Variable1;
/* display value of other variables */
cout << “Variable2 = “ << Variable2; */
compiler error here
Fundamental Programming

39. Multi-line Statements
compilers treat an end-of-line in C++ as white space – so:
cout << “Variable1 = “ << Variable1;
MyVeryLongVariableName = <my very long expression>;
is same as:
cout << “Variable1 = “
<< Variable1;
MyVeryLongVariableName =
<my very long expression>;
Fundamental Programming

40. That’s the end of
“Back to Basics” !
Fundamental Programming