x = 5; y = 6; // Assign Values
z = x + y; // Compute Values
- Fixed values
- Variable values
Fixed values are called
Variable values are called
The two most important syntax rules for fixed values are:
are written with or
are text, written within double or single quotes:
In a programming language,
are used to
is used to
In this example, x is defined as a variable. Then, x is
assigned (given) the value
x = 6;
values to variables:
x = 5;
y = 6;
An expression is a combination of values, variables, and operators,
which computes to a value.
The computation is called an evaluation.
For example, 5 * 10 evaluates to 50:
Expressions can also contain variable values:
The values can be of various types, such as numbers and strings.
For example, “John” + ” ” + “Doe”, evaluates to “John Doe”:
are used to
identify actions to be performed.
keyword tells the browser to create variables:
x = 5 + 6;
y = x * 10;
Code after double slashes
is treated as a
Comments are ignored, and will not be
// var x = 6; I will
NOT be executed
You will learn more about comments in a later chapter.
Identifiers are names.
functions, and labels).
The rules for legal names are much the same in most programming languages.
dollar sign ($).
Subsequent characters may be letters, digits, underscores, or dollar signs.
Numbers are not allowed as the first character.
easily distinguish identifiers from numbers.
are two different variables:
lastName = “Doe”;
lastname = “Peterson”;
as the keyword
Historically, programmers have used different ways of joining multiple words into one variable name:
first-name, last-name, master-card, inter-city.
first_name, last_name, master_card, inter_city.
Upper Camel Case (Pascal Case):
FirstName, LastName, MasterCard, InterCity.
Lower Camel Case:
firstName, lastName, masterCard, interCity.
Unicode covers (almost) all the characters, punctuations, and symbols in the world.
For a closer look, please study our
Complete Unicode Reference