2.1.1 Thinking abstractly

define abstraction

the process of removing unnecessary details from a problem

representational abstraction

analysing what is relevant and simplifying a problem based on this information

Abstraction by generalisation

grouping together similarities within a problem tp identify what kind of problem it is

why do abstraction by generalisation

allows certain problems to be categorised as being of a particular type so a common solution can be used to solve these problems

Data abstraction

details about how data is being stored are hidden. Programmers can make use of abstract data structures without concerning themselves about how they are implemented.

Procedural abstraction

Programmers can perform functions without having knowledge about the code used to implement this functionality.. Once a procedure has been coded, it can be reuses as a black-box

Levels of abstraction

the highest levels of abstraction are closes to the user and are usually responsible for providing n interface to the user to interact with hardware. Lowest levels of abstraction are responsible for actually performing these tasks through the execution of machine code

Pros of abstraction

allows non experts to make used of a range of systems or models by hiding info that is too complex; more efficient design as programmers can focus on the key elements; less time spent coding;

why are levels of abstraction used

to handle large, complex problems by separating tasks - higher levels deal with user interaction while low levels execute machine code

what is meant by layers of abstraction in programming languages

the distinction between low-level and high-level languages - each layer hides complexity from the one above it

low level vs high level langauges 

low level is closer to machine code, harder write and requires hardware knowledge; high level is easier to lear and closer to natual language and hides machine-lvel detail 

how does the TCP/IP use abstration

it divides network communication itno four laters, each handlind a different function and hiding details from the others

why are standards important in layered in layered models it TCP/IP?

they ensure compatability and allow layers to work independently while following agreed protocols

abstraction vs reality 

abstraction simplifies real-world entities into computational models like variables or objects 

how does OOP use abstraction

objects represent real-world entities, attributes model characterisitics and methods model actions

what does designing a solution involve

thinking ahead about how different components of a problem will be handled in the best way possible

why is thinking ahead important 

it helps developers anticipae potential issues and make programs easy and inuitive to use 

what are the three main parts of any computations problem

inputs, processing and outputs

what are te inputs in a computational problem

data entered into a system by the user that is required to solve a problem

what are outputs in a computational problem 

the results produced after the iputs have been processed 

what must designers decide when handling input and ot=utput

suitable data types, data structures and methods to capture and present the solution

what order should designers consider inputs and outputs

start by identifying required outputs, then determine the inputs and processing needed to achieve them

what are preconditions 

requirements that mist be met before a program or subroutine executes 

what happens if preconditions arent met

the prigram may fail to run or return ivalid results

why are preconditions useful

they let a subroutine safely assume that input arguments meet certain criteria

where can preconditions be defined 

within the code itself or in the documentaiton accompanying the program 

what does including preconditions in the documentation achieve

reduces program length and complexity, and saves debugging and maintenance time

why do peconditions promote reusability

they ensure necessary checks are made before execution so the subroutine can be safely reused

what is caching

storing recently used instructions or data in cache memory so they can be accessed faster later 

why is caching useful

it avoids repeatedly fetching data from slower secondary storage, saving time and improving performance

eg of caching

web browsers cache frequently visited pages to speed up loading and reduce bandwidth usage

what is prefetcing 

a technique where alogrithms predct and preload data or instryctions likely ot be needed soon 

what limits the effectiveness of prefetching and caching

accuracy of prediciton alogrithms and the limited size and search speed of cache memory

main advanatge of caching and prefetching

significantly improved performance if implemented correctly

what are reusable program components 

pre-written, tested pieces of code that can be used in multiple programs 

where are reusable components stored

in libraries

why is decomposition useful when designing software

it breaks the problem into smaller tasks, making it easier to identify reusable components

eg of reusable components 

stacks, queues, classes, subroutines 

pros of reusable components

savs time, money and resources sunce theyre already tested and reliable ; can be reused in future projects so reduces development costs

limitation of reusable components

compatability issues may arise which may require modification work which may be more costly than developing in-house

why is thinking procedurally useful

it simplifies the program design, allows easier testing and debugging, enables teamwork by dividing tasks, and makes t easier to modify and reuse components later

what is the first stage of thinking procedurally 

probelm decomposition - taking the problem defined by the user and breaking it down into smaller subproblems that are easier to solve 

define problem decomposition

the process of splitting a large,cimplex problem into smaller, more manageable subproblems, each which can be solved separately

pros of problem decomposition

makes the overall problem easier to manage, allows different peopple to work on different parts accoridng to their skills, and supports modular, testable program design

top-down design 

involves starting with the overall problem and progressively breaking it into smaller and smaller subproblems until each can be implemented as a single, specific task

pros of top down design

It helps structure complex problems into logical levels, where higher levels show the overall structure, and lower levels define detailed tasks. This allows clearer design, independent development, and easier testing.

aim of top-down design

o keep decomposing the problem until each subproblem can be represented as a single, self-contained task or subroutine that can be coded and tested individually

what ahppens after all the components are identified

They are combined and integrated into a complete working program, ensuring that each subroutine interacts correctly with others

Why is the order of operations important when combining subroutines?

Some subroutines depend on data from others. Executing them in the wrong order can cause errors or illogical results, so programmers must plan the correct sequence of operations

when can subroutines be executed simultaneously

iProblem decomposition → Split problem into subproblems

• Top-down design → Refine subproblems into simple tasks

• Identify components → Decide how to implement each part

• Combine solution → Integrate subroutines into a full program

• Determine execution order → Arrange subroutines logically and efficientlyf they don’t depend on the same data or inputs, multiple subroutines can be executed simultaneously (parallel execution)

summarise thinking procedurally 

• Problem decomposition  

• Top-down design

• Identify components

• Combine solution

• Determine execution order

define a decision

The result reached after some consideration

why is decision making important

it allows programmers to choose the most effective approach for solving a problem

eg of making decisions in software development

choosing the programming paradigm, choosing input and output devices, deciding how to collect and process data

how to simplify the decision making process

by narrowing down possible options based on feasibility, functionality and familiarity - eg choosing a programming language that suits the problem

why is it important to identify where decisions need to be made

so enough info can be gathered about the available options, allowing informed secisions that lead to more effective and efficient solutions

main factors influencing the outcome of decisions

effectiveness, convenience, feasibility 

how to evaluate factors when making decisions

rank the factors by importance. this prioritisation hekps determine the most suitable option

what is the effect of decisions on a program’s flow

they determine the route the program follows. depending on the user’s input or internal logic, different sections of the code may execute, leading to varied outcomes

thinking logically meaning 

identifying where and when decisions must be made, planning all possible outcomes and structuring the program to handle each scenario appropriately

summarise decision making

• Identify where decisions need to be made

• Gather information and options

• Evaluate options based on effectiveness, convenience, and feasibility

• Prioritise key factors

• Choose and implement the best solution

• Reflect on the decision’s outcome and adjust if necessary

what is concurrent processing 

completing more than one task at a given time. This doesnt mean that mutiple tasks have to be done at once, it means different tasks are given slices of processor time to give the illusion that tasks are being performed simultaneously 

what is concurrent thinking

the mindset that allows you to spot patterns and parts of problems where concurrency can be applied

how to fetermine the parts of the problem that can be solved concurrently

first asses which parts of the problem are relatedand these can often be dealt concurrently

difference between concurrent processing and concurrent thinking 

concurrent processing uses a computer processor while thinking uses your brain 

concurrent processing vs parallel processing

parallel processing uses multiple processes to complete more than one task simultaneously but concurrent processing is when one task is given a slice of processor time to make it look like tasks are bign completed simultanously when in reality they are executed sequentially

proces of concurrent processing

thenumber of tasks completed in a givent ime is increased; less time is wasted waiting for an input or user interaction as other tasks can be completed

cons of concurrent processing 

it can take a longer time to complete when large numbers of users or tasks are involved as processes cannot be completed at once; there is an overhead in coordinating and switching between processing which reduces program throughput; just as with parallel processing, not all tasks are suited to being broken up and performed concurrently