This document provides an overview of basic C programming concepts including variables, data types, arithmetic operations, conditionals, loops, functions, pointers, arrays, structs, enums, and static variables and functions. It explains how to declare and assign variables, use basic math operators, write if/else and switch statements, iterate with while and for loops, define custom data types with typedef, create aggregate data structures with structs, define enumerated types with enums, store multiple values in arrays, reference memory with pointers, separate function declarations from implementations, and limit scope with the static keyword.

1. TECNOLOGIAS EMERGENTES EM JOGOS
Engenharia em Desenvolvimento de Jogos Digitais - 2013/2014
February 14, 2014
Daniela da Cruz
dcruz@ipca.pt

2. C BASICS

3. C basics
C COMMENTS
There are two ways to include commentary text in a C program.
→
Inline comments
// This is an inline comment
→
Block comments
/* This is a block comment.
It can span multiple lines. */
3

4. C basics
C VARIABLES
Variables are containers that can store dierent values.
type name
the = operator.
To declare a variable, you use the
to assign a value to it you use
syntax, and
double odometer = 9200.8;
int odometerAsInteger = (int)odometer;
4

5. C basics
C CONSTANTS
The const variable modier tells to the compiler that a variable is
never allowed to change.
double const pi = 3.14159;
5

6. C basics
C ARITHMETIC
The familiar +, -, *, / symbols are used for basic arithmetic
operations, and the modulo operator (%) can be used to return the
remainder of an integer division.
printf(6
printf(6
printf(6
printf(6
printf(6
+
*
/
%
2
2
2
2
2
=
=
=
=
=
%d,
%d,
%d,
%d,
%d,
6
6
6
6
+
*
/
2);
2);
2);
2);
6 % 2);
// 8
// 4
// 12
// 3
// 0
6

7. C basics
C ARITHMETIC (2)
C also has increment (++) and decrement () operators. These are
convenient operators for adding or subtracting 1 from a variable.
int i = 0;
printf(%d, i);
i++;
printf(%d, i);
i++;
printf(%d, i);
// 0
// 1
// 2
7

8. C basics
C RELATIONAL/LOGICAL OPERATORS
The most common relational/logical operators are shown below.
Operator
a == b
Description
Equal to
!=b
b
a = b
a b
a = b
Greater than or equal to
!a
Logical negation
a
a
Not equal to
Greater than
Less than
Less than or equal to
a b
Logical and
||
Logical or
a
b
8

9. C basics
C CONDITIONALS
C provides the standard if statement found in most programming
languages.
int modelYear = 1990;
if (modelYear 1967) {
printf(That car is an antique!!!);
} else if (modelYear = 1991) {
printf(That car is a classic!);
} else if (modelYear == 2014) {
printf(That's a brand new car!);
} else {
printf(There's nothing special about that car.);
}
9

10. C basics
C CONDITIONALS (2)
C also includes a
integral types
switch
statement, however it
only works with
not oating-point numbers, pointers, or
Objective-C objects.
switch (modelYear) {
case 1987:
printf(Your car is from 1987.); break;
case 1989:
case 1990:
printf(Your car is from 1989 or 1990.); break;
default:
printf(I have no idea when your car was made.);
break;
}
10

11. C basics
C LOOPS
The
while
the related
for loops can be used for iterating over values,
break and continue keywords let you exit a loop
and
and
prematurely or skip an iteration, respectively.
int modelYear = 1990;
int i = 0;
while (i5) {
if (i == 3) {
printf(Aborting the while-loop);
break;
}
printf(Current year: %d, modelYear + i);
i++;
}
11

12. C basics
C LOOPS (2)
int modelYear = 1990, i;
for (i=0; i5; i++) {
if (i == 3) {
printf(Skipping a for-loop iteration);
continue;
}
printf(Current year: %d, modelYear + i);
}
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13. C basics
C TYPEDEF
The
typedef
keyword lets you create new data types or redene
existing ones.
typedef unsigned char ColorComponent;
int main() {
ColorComponent red = 255;
return 0;
}
13

14. C basics
C STRUCTS
A struct is like a simple, primitive C object. It lets you aggregate
several variables into a more complex data structure, but doesn't
provide any OOP features (e.g., methods).
typedef struct {
unsigned char red;
unsigned char green;
unsigned char blue;
} Color;
int main() {
Color carColor = {255, 160, 0};
printf(Your color is (R: %u, G: %u, B: %u),
carColor.red, carColor.green, carColor.blue);
return 0;
}
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15. C basics
C ENUMS
The
enum
keyword is used to create an enumerated type, which is a
collection of related constants.
typedef enum {
FORD,
HONDA,
NISSAN,
PORSCHE
} CarModel;
int main() {
CarModel myCar = NISSAN;
return 0;
}
15

16. C basics
C ARRAYS
The higher-level
the
NSArray
and
NSMutableArray
classes provided by
Foundation Framework are much more convenient than C
arrays.
int years[4] = {1968, 1970, 1989, 1999};
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17. C basics
C POINTERS
A pointer is a direct reference to a memory address.
→
The reference operator () returns the memory address of a
normal variable. This is how we create pointers.
→
The dereference operator (*) returns the contents of a
pointer's memory address.
int year = 1967;
int *pointer;
pointer = year;
printf(%d, *pointer);
*pointer = 1990;
printf(%d, year);
17

18. C basics
C FUNCTIONS
There are four components to a C function: its return value, name,
parameters, and associated code block.
18

19. C basics
C FUNCTIONS
Functions need to be dened before they are used.
C lets you separate the
implementation.
→
declaration of a function from its
A function declaration tells the compiler what the function's
inputs and outputs look like.
→
The corresponding implementation attaches a code block to
the declared function.
Together, these form a complete function denition.
19

20. C basics
C STATIC FUNCTIONS
The
static
keyword let us alter the availability of a function or
variable.
By default, all functions have a global scope.
This means that as soon as we dene a function in one le, it's
immediately available everywhere else.
The
static
specier let us limit the function's scope to the current
le, which is useful for creating private functions and avoiding
naming conicts.
20

21. C basics
C STATIC FUNCTIONS (2)
File
functions.m:
// Static function declaration
static int getRandomInteger(int, int);
// Static function implementation
static int getRandomInteger(int minimum, int maximum) {
return ((maximum - minimum) + 1) + minimum;
}
You would not be able to access
main.m.
getRandomInteger()
from
Note that the static keyword should be used on both the function
declaration and implementation.
21

22. C basics
C STATIC VARIABLES
Variables declared inside of a function are reset each time the
function is called.
However, when you use the
static
modier on a local variable, the
function remembers its value across invocations.
22

23. C basics
C STATIC VARIABLES (2)
int countByTwo() {
static int currentCount = 0;
currentCount += 2;
return currentCount;
}
int main(int argc, const char * argv[]) {
printf(%d, countByTwo());
// 2
printf(%d, countByTwo());
// 4
printf(%d, countByTwo());
// 6
}
return 0;
23

24. C basics
C STATIC VARIABLES (2)
This use of the static keyword
does not aect the scope of local
variables.
Local variables are still only accessible inside of the function itself.
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25. C basics
C SUMMARY
We reviewed:
→
Variables
→
Conditionals
→
Loops
→
Typedef
→
Struct's
→
Enum's
→
Arrays
→
Pointers
→
Functions
→
Static (functions and variables)
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