Variables and Types
C has several types of variables, but there are a few basic types:
- Integers - whole numbers which can be both positive and negative. Defined using
- Unsigned integers - whole numbers which can only be positive. Defined using
unsigned long or
unsigned long long.
- Floating point numbers - real numbers (numbers with fractions). Defined using
- Structures - will be explained later, in the Structures section.
The different types of variables define their bounds. A
char can range only from -128 to 127, whereas a
long can range from -2,147,483,648 to 2,147,483,647 (
long and other numeric data types may have another range on different computers, for example - from –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 on 64-bit computer).
Note that C does not have a boolean type. Usually, it is defined using the following notation:
#define BOOL char
#define FALSE 0
#define TRUE 1
C uses arrays of characters to define strings, and will be explained in the Strings section.
For numbers, we will usually use the type
int, which an integer in the size of a "word" the default number size of the machine which your program is
compiled on. On most computers today, it is a 32-bit number, which means the number can range from -2,147,483,648 to 2,147,483,647.
To define the variables
bar, we need to use the following syntax:
int bar = 1;
foo can be used, but since we did not initialize it, we don't know what's in it. The variable
bar contains the number 1.
Now, we can do some math. Assuming
e are variables, we can simply use plus, minus and multiplication operators
in the following notation, and assign a new value to
int a = 0,b = 1,c = 2,d = 3, e = 4;
a = b - c + d * e;
printf("%d", a); /* will print 1-2+3*4 = 11 */
In the next exercise, you will need to create a program which prints out the sum of the numbers