C

General Skills

Constants - Variables - Data Types

There are 9 types of data types. These include:

• boolean
• string
• integer
• double
• decimal
• character
• byte
• float
• long

To declare a variable you state the data type followed by the name of the variable:

DataType VariableName;

You can declare and assign a variable at the same time:

DataType VariableName = Value;

Examples

Boolean is a binary value, being either true or false.

bool example = true;

String is used for storing characters in word form (note the double quotes "").

string example = "hello world";

Integer is used to store whole numbers (32 bit values).

int example = 457568368;

Double is used to store numbers where there are numbers before and after the decimal point, using 64 bits of memory.

double example = 3.3;

Decimal is used to store larger numbers with information before and after the decimal point, using 128 bits of memory.

decimal example = 12.593;

Character is used to store single letters (note the single quotes ).

char example = 'A';

Byte is used to store a byte (eight bits). In C#, it is specifically an 8 bit integer (0-255).

byte example = 255;

Float is used to store a 32 bit decimal number, which must be defined as being a float using "F" or "f" to distinguish it from a double, or it may cause compilation errors.

float example = 9.4F;

Long integer is also used to store whole numbers (However these are 64 bit values).

long example = 7846354759340276482;

Local vs Global

It is important to know that a variable declared within a block is only available within that block, it doesn't exist outside of the block. These would therefore be local variables, because they are local to where they are declared.

You can therefore declare variables within your program and declare them outside of any block, these variables will be available anywhere within your program. These are called global variables, because they can be used throughout the program.

Constants

Constants are used to create a variable of a specified data type that can never be changed after declaration.

During runtime, once the constant is set the value cannot change during the execution of the program.

The only way to change it is to edit the code and re-compile.

const int example = 32

Advanced skills

Text Files

Binary Files

Handling Exceptions