CPIT

A computer

Includes hardware and software, stores and process data

Hardware

The physical elements of the computer. Eg: Monitor, Speaker, Mouse, RAM, computer case

Software

Invisible instructions that control hardware. Eg: Word & Powerpoint

Bus

Subsystem that interconnects the computer components, found inside of the motherboard

Bus

Output devices

Sends data from a computer to another device or user, (audio video text graphics) Eg: Monitor (which displays text and graphics), speakers, printers.

Resolution and dot pitch

Determines the quality of the display

Input devices

Send data to a computer, Eg: keyboard and mice

CPU (central processing unit)

Brain of the computer, retrieves instructions from memory.

CPU speed

MHz=1 million pulses per second

Memory

• stores data and program instructions

• Saves ordered sequences of bytes (each byte=8bits)

• Volatile, lost once power is off

• Lost whenever new info replaces the old info

Storage devices

Permanently stored & nonvolatile Eg: Disk drives (hard & floppy), CD drives (CD-R, CD-RW) and tape drives (magnetic tape)

Programs

Software that has instructions for the computer. Are written using programming languages

Machine languages

Primitive instructions, binary code, difficult to read and modify by user. Native language. Eg: 10100110

Assembly language

Difficult to understand by the computer, needs an assembler to change (convert) the assembly code to machine code. Eg: ADD 2, 3, result

High level languages

Easy to understand, english-like. Needs an interpreter or compiler to convert this language to machine code. Eg: Area=5×5×3.1415

High level language examples

Python, C++, C#, Java, COBOL, Visual basic, Ada, Pascal

Statement

Instructions in high-level language

Source code/ program

A program in high-level language

Interpreter/compiler

Translates the high-level code to machine code

Interpreter

Reads one statement and then changes it to machine code (one by one)

Compiler

Translates the entire source code to machine code (all together)

Operating system (OS)

Program that manages and controls computer activities eg: windows 10, linux, macOS

Application program

Cannot run without an operating system. Eg: internet browser, word

General purpose

High level language used in google search, nasa projects, python is interpreted and needs an interpreter

Interpreted

Interpreted one statement at a time

Object oriented

Objects created by classes

Reuse-able software

It relies on the object oriented software, making it easier to use the code in more than one place.

Class

A type that defines the objects pf the same kind with properties and methods

open source program

Software released under a license that the copyright holder gives the rights to change, or study and then distribute to anyone. Eg: two types of python interpreters

Interactive mode

A quick way of running python code, used in python shell.

> > > means shell is ready to use

Results are returned directly after enter. Cannot be edited

Code tracing

Interprets the results of each code line, and keeps track of the effect of each code statement.

Statement

Action or sequence of actions. Eg: print(“Welcome to python”)

Programming style

Easy to read and understand. Python is case sensitive

Documentation

Body of explanatory remarks and comments

Comment

A programmer readable explanation that is ignored by the interpreter. Starts with #

Script mode

Script mode (normal mode) is written in a text file with the extension .py. Result is returned as a full file after being created and saved. Can be edited

Python

General purpose, interpreted, object oriented

Overflow error

Variable with too large of a value

Underflow error

Variable with too small of a value

String + string

Concatenation of strings

Number + number

Sum of numbers

String + number

Error (type error)

Syntax error

Error in code construction

Mistyped statement (Syntax)

Y=4

X=

Print(x)

Incorrect indentation (syntax)

Print(“hello”)

X=3

Print(x)

Incorrect parenthesis (syntax)

print(3+5

print(“hello”)

Punctuation (syntax)

print(“Hello).

Runtime error

Causes the program to terminate abnormally (abort) and detected by the interpreter

Input mistake (runtime)

Divided by zero:

x=0

print(10/x)

Entering a string value whilst the expected result is numbers:

area=input (“Enter area”)

A variable with an unidentified value:

x=4

print(y+x)

Calculation with non numeric values:

x=‘4’

y=3

print(x+y)

Logic error

Causes incorrect output (or unexpected results)

Direct value assignment

x=3

Assigning a value from an expression result

x=4+6

or

y=4

x=y+6

Assigning a value taken from the user through the keyboard

x=input(“enter the value”)

assign one value to multiple variables

a=b=k=3

assign multiple values to multiple variables in one line

a,b,c=4,3.5,”ahmed”

or a,b,c=input(“enter three variables”

Swap values between two variables

x=3

y=5

x,y=y,x

string

anything between ‘’

integer numbers (int)

whole numbers

Float numbers (float)

fractions

boolean

True/False

Operators precedence

import time time.time()

returns number of milliseconds since 1970

import math

returns math module functions

Current time

eval()

Converts a value to its original type

input()

Reads the value from the user via the keyboard

print()

Prints a value

int()

Converts a value to an integer

str()

converts a value into a string

bool()

converts a value into true(1) or false(0)

abs(x)

Returns absolute value

max(x1,x2,x3)

returns the largest value

min(x1,x2,x3)

returns the smallest value

pow(x,y)

x to the power of y

round(x)

rounds to the nearest whole number (integer result)

round(x,y)

rounds to a specific number of decimal places (float result)

math.pi

returns pi (3.14159)

math.e

returns value of 2.71828 (eulers number)

fabs(x)

returns absolute value in decimal/float form

ceil(x)

rounds up to the nearest integer

floor(x)

rounds x to the smallest integer

exp(x)

returns e to the power of x

log(x)

log(number) using base e

log(x,base)

Log x by base of base

sqrt(x)

square root of x

sin(x)

sin of x

asin(x)

sin-1 of x

cos(x)

cos of x

acos(x)

cos-1 of x

tan(x)

tan of x

degrees(x)

converts radians to degrees

radians(x)

converts degrees to radians

importance of degrees/radians functions

sin/cos/tan functions work in radians, so you have to convert them to degrees

bool(x)

converts number (integer) into true or false (boolean)

int(bool(x)) or int(boolean)

converts boolean into integer

Float division

one / with decimal placements

Integer division

two // no decimal placements

in the situation that one of the numbers has decimals the result will always be x.0 (eg 2.2//1 will be 1.0)

modulus or remainder

%

if first number is smaller than second number, the output will be the first number. If not, regular output.