Python Data Structures: Dictionaries, Strings, and Functions
Python Data Structures Fundamentals
Dictionaries: Key-Value Storage
A Python dictionary is a collection of key-value pairs used to store data in an unordered, mutable structure. You create a dictionary using curly braces {} with key-value pairs, for example: my_dict = {"name": "Alice", "age": 25}. You can also use the dict() constructor to create dictionaries.
Accessing values is done by referring to their keys: my_dict["name"] returns “Alice”.
Adding, Updating, and Removing Items
You add or update items
Read MoreFlip-Flops, Registers, and Sequential Circuit Fundamentals
Flip-Flops: Basic Sequential Data Storage
A Flip-Flop is a basic sequential circuit used to store one bit of data (0 or 1). Unlike combinational circuits, the output of a flip-flop depends on:
- Present input
- Previous output (memory)
- Clock signal
Flip-flops are the building blocks of registers, counters, and memory units.
1. RS (Set-Reset) Flip-Flop
The RS flip-flop has two inputs: S (Set) and R (Reset).
Working Principle
- S = 1 → Output is set to 1
- R = 1 → Output is reset to 0
- S = R = 0 → No change
- S =
PHP Fundamentals: Control Flow, Arrays, and Functions
Core PHP Concepts
Control Statements
Control statements manage the flow of execution based on conditions or repetitions.
Conditional Statements
if...else: Executes code if a condition is true.switch: Selects one of many code blocks to be executed based on a variable’s value.
Looping Statements
for: Used when the number of iterations is known.while: Repeats execution as long as a specified condition remains true.foreach: Specifically designed to iterate through arrays.
File Handling Operations
PHP allows
Read MoreEssential Linux Commands, User Roles, and Process States
Common Linux Commands and Utilities
The commands listed below are a mix of standard Unix/Linux utilities and internal shell commands. Below is the syntax and purpose for the most common interpretations in a Linux environment.
1. stat (st) 📊
The command st is not a standard standalone utility, but it is often used as a shortcut or abbreviation for the stat command.
- Syntax (using stat):
stat [OPTION]... FILE... - Purpose: The
statcommand displays detailed information about a file or file system. This
Essential Computer Fundamentals and Software Systems
Evolution of Computer Generations
The history of computing is categorized into generations, defined by the fundamental electronic technology used. This evolution has led to continuous improvements in speed, size, cost, and efficiency.
| Generation | Approximate Period | Core Technology | Key Features | Examples |
|---|---|---|---|---|
| First | 1940 – 1956 | Vacuum Tubes | Enormous size, very slow, high heat output, used Machine Language. | ENIAC, UNIVAC I |
| Second | 1956 – 1963 | Transistors | Smaller, faster, more reliable, used Assembly Language and early High- |
Java Variables, Objects, Static and Instance Members
Java Variables and Object Concepts
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Four kinds of variables
There are four kinds of variables:
- Local variables are those declared in method bodies; these appear in the variable portion of a Java execution frame. Unless explicitly requested, you generally do not need to show execution frames in an object diagram.
- Instance variables are non-static variables declared within a class body; these appear within an instance object box (see the discussion of objects below).
- Class variables are static variables