Basic Syntax and VariablesIn programming, understanding basic syntax and how to use variables is fundamental.
Basic Syntax refers to the set of rules that define how a program should be written and structured in a particular programming language. It dictates the valid combinations of keywords, operators, and symbols to form executable instructions. Key components of basic syntax include:
- Keywords: Reserved words that have special meaning in the language (e.g., `if`, `else`, `for`, `while`, `print`).
- Identifiers: Names given to variables, functions, and other program elements. They must follow specific naming rules (e.g., cannot start with a number, usually case-sensitive).
- Operators: Symbols that perform operations on values and variables (e.g., arithmetic operators like `+`, `-`, `-`, `/`; assignment operator `=`, comparison operators `==`, `>`).
- Statements: A complete instruction that the program executes (e.g., `x = 10`, `print("Hello")`).
- Expressions: Combinations of values, variables, and operators that evaluate to a single value (e.g., `10 + 5`, `age > 18`).
- Comments: Non-executable lines of code used by programmers to explain parts of the code. They are ignored by the compiler or interpreter.
Variables are named storage locations that hold data in a computer program. They act as containers for values that can change during the program's execution. Each variable typically has:
- A Name: An identifier that allows you to refer to the storage location.
- A Value: The actual data stored in the location.
- A Data Type: This specifies the type of data the variable can hold (e.g., integer for whole numbers, float for decimal numbers, string for text, boolean for true/false). Some languages require you to explicitly declare the data type (statically typed), while others infer it from the assigned value (dynamically typed).
Declaration and Assignment: Before using a variable, it often needs to be declared (created). After declaration, a value can be assigned to it using the assignment operator (commonly `=`).
Understanding these core concepts is crucial for writing any functional program, as they form the building blocks for all more complex programming constructs.
Example Code
Python Example for Basic Syntax and Variables
1. Comments: Lines starting with '' are ignored by the interpreter.
This is a single-line comment.
'''
This is a multi-line comment, or a docstring if placed right after a function/class definition.
For general multi-line comments, you can use triple quotes as shown.
'''
2. Variable Declaration and Assignment
Python is dynamically typed, so you don't declare the type explicitly.
The type is inferred from the assigned value.
Integer variable
age = 30
Float variable (decimal number)
price = 19.99
String variable (text)
name = "Alice"
Boolean variable (True/False)
is_active = True
Re-assigning a variable (changing its value)
score = 100
score = 120 The value of 'score' is now 120
3. Basic Operations with Variables
Arithmetic operations
num1 = 10
num2 = 5
sum_result = num1 + num2 Addition
diff_result = num1 - num2 Subtraction
prod_result = num1 - num2 Multiplication
div_result = num1 / num2 Division (results in float)
int_div_result = num1 // num2 Integer division (results in int)
mod_result = num1 % num2 Modulus (remainder)
pow_result = num1 num2 Exponentiation (10 to the power of 5)
String concatenation
greeting = "Hello, " + name + "!"
4. Printing Variable Values (Output)
The 'print()' function is a fundamental statement for displaying output.
print("----------------------------------")
print("Variable Values:")
print("Age:", age) Output: Age: 30
print("Price:", price) Output: Price: 19.99
print("Name:", name) Output: Name: Alice
print("Is Active:", is_active) Output: Is Active: True
print("Score:", score) Output: Score: 120
print("\nArithmetic Results:")
print("Sum:", sum_result) Output: Sum: 15
print("Difference:", diff_result) Output: Difference: 5
print("Product:", prod_result) Output: Product: 50
print("Division:", div_result) Output: Division: 2.0
print("Int Division:", int_div_result) Output: Int Division: 2
print("Modulus:", mod_result) Output: Modulus: 0
print("Power:", pow_result) Output: Power: 100000
print("\nString Concatenation:")
print(greeting) Output: Hello, Alice!
print("----------------------------------")