Computer Systems Basics

Study Notes

A computer is an electronic device that takes input, processes it, stores data, and produces output.

Fixed computers perform a specific task and cannot be programmed to do anything else.
Programmable computers can be programmed to perform a variety of tasks.

Calculators are special-purpose computers that perform mathematical calculations.
Computers are general-purpose devices that can perform various tasks beyond calculations.

RAM (Random Access Memory) is volatile memory that temporarily stores data and program instructions while the computer is running.
ROM (Read-Only Memory) is non-volatile memory that permanently stores data and cannot be changed.

Secondary storage is necessary because RAM is volatile and limited in capacity.
Types of secondary storage: hard disk drives, solid-state drives, magnetic tapes, CDs, DVDs, Blu-ray discs.
Technologies used: magnetic, optical, solid-state.

Binary is a number system with base 2, using only 0s and 1s.
Converting Denary to Binary:
- Divide the denary number by 2 and note the remainder.
- Repeat step 1 until the quotient is 0.
- The binary representation is the sequence of remainders in reverse order.
Converting Binary to Denary:
- Multiply each binary digit (starting from the right) by 2 to the power of its position (starting from 0).
- Add the products to obtain the denary equivalent.

Adding three binary numbers together:
- Perform binary addition for each column (right to left).
- Carry over any overflow to the next column.

Abstraction: breaking down complex problems into smaller, more manageable parts to focus on essential features
Decomposition: dividing a problem into smaller, more manageable parts to solve individually
Pattern Recognition: identifying and understanding patterns in data to make informed decisions

An algorithm is a clear, step-by-step procedure to solve a problem or achieve a specific goal
Representing Algorithms:
- Flowcharts: using shapes to visually represent the flow of an algorithm (e.g., input, process, output)
- Correct use of shapes: using rectangles for processes, diamonds for decisions, and arrows for direction
Identifying parts of an algorithm:
- Inputs: data or information entered into the algorithm
- Processing: steps that manipulate or transform the input data
- Outputs: results or outcomes of the algorithm

The order of steps in a program or algorithm: following a specific sequence to achieve a desired outcome

Identifying selection in a program or algorithm:
- If-else statements: making decisions based on conditions
- Understanding where and how to use selection statements

Repetition in a program or algorithm:
- While loops: repeating a sequence of steps until a condition is met
- For loops: repeating a sequence of steps for a specified number of iterations
- Understanding what to include in a loop

Purpose of variables: storing and manipulating data in a program or algorithm
Assigning and changing variable values:
- Storing data in a variable
- Updating or modifying variable values

Main data types: understanding the types of data that can be stored in a variable (e.g., integers, strings, etc.)
Casting data types: converting data types during input to ensure correct processing