A computer program is a list of "instructions" to be "executed" by the computer.
In a programming language, these program instructions are called statements.
var y = 3;
var z = x + y; </script>
Values, Operators, Expressions, Keywords, and Comments.
Fixed values are called literals. Variable values are called variables.
The most important rules for writing fixed values are:
Numbers are written with or without decimals:
Strings are text, written within double or single quotes:
In a programming language, variables are used to store data values.
An equal sign is used to assign values to variables.
In this example, x is defined as a variable. Then, x is assigned (given) the value 8:
x = 8;
var y = 8;
An expression is a combination of values, variables, and operators, which computes to a value.
The computation is called an evaluation.
For example, 6* 18 evaluates to 108:
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":
The var keyword tells the browser to create a new variable:
var y = x * 50;</script>
Code after double slashes // or between /* and */ is treated as a comment.
Comments are ignored, and will not be executed:
// var x = 3; I will NOT be executed</script>
Identifiers are names.
The rules for legal names are much the same in most programming languages.
Subsequent characters may be letters, digits, underscores, or dollar signs.