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Outline
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Introduction
Hardware
Software
How Computers Store Data
How Programs Work
Using Python

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Introduction
● Computers can

Perform calculations efficiently
○ Remember a huge amount of results and data
○ Be programmed
● A Program is a set of instructions that a computer follows to
perform a task
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Commonly referred to as Software

● Programmer is a person who can design, create, and test programs
○ Also known as software developer/engineer
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Hardware
● Hardware: The physical devices that make up a computer
○ Computer is a system composed of several components that all
work together
● Typical major components:
○ Central processing unit (CPU)
○ Main memory (RAM)
○ Secondary storage devices
○ Input and output devices
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Hardware (cont
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)

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Input and Output (I/O)
● Input: data the computer collects from people and other devices
● Input device: component that collects the data
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Examples: keyboard, mouse, touchscreen, scanner, camera
Disk drives can be considered input devices because they load programs into the
main memory

● Output: data produced by the computer for other people or devices
○ Can be text, image, audio, or bit stream
● Output device: formats and presents output
○ Examples: video display, printer
○ Disk drives and USB drives can be considered output devices because data is
sent to them to be saved
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Software
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Everything the computer does is controlled by software
General categories:
○ Application software
○ System software
Application software: programs that make computer
useful for everyday tasks
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Examples: word processing, email, games, and Web
browsers
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Software (cont’d)
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System software: programs that control and manage
basic operations of a computer
○ Operating system: controls operations of hardware
components
○ Utility Program: performs specific task to enhance computer
operation or safeguard data
○ Software development tools: used to create, modify, and
test software programs
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How Computers Store Data
● All data in a computer is stored in sequences of 0s and 1s
● Byte: just enough memory to store letter or small number
○ Consists of eight bits
○ Bit: electrical component that can hold positive or negative
charge, like on/off switch

○ The on/off pattern of bits represents data
stored in the byte
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How Computers Store Data (cont’d)
● Binary digit (bit) represents two values: 0 and 1
● Computers use binary numbering system (base 2)
Binary Code: a sequence of zeros and ones
j-1
○ Position of bit j is assigned the value 2
○ Determine the value of binary code: sum position values of the bits equal to
1s
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● 𝑥𝑘𝑥𝑘−1…𝑥0 in base 2 → 2k × 𝑥𝑘 + 2k-1 × 𝑥𝑘−1+ … + 𝑥0
○ Example: 1101 in base 2 = ?

● Byte size limits are 0 and 255
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0 = all bits off; 255 = all bits on
To store larger number, use several bytes
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How Computers Store Data (cont’d)
● Characters are converted to numeric code of fixed size
● Most important coding scheme is ASCII
○ ASCII is limited: defines codes for only 128 characters
● Unicode coding scheme becoming standard
○ Compatible with ASCII
○ Can represent characters for other languages

● Digital: describes any device that stores data as binary numbers
● Digital images are composed of pixels
○ To store images, each pixel is converted to a binary number representing the
pixel’s color

● Digital music is composed of sections called samples
○ To store music, each sample is converted to a binary number
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How Programs Work
● CPU designed to perform simple operations on pieces of data
○ Examples: reading data, adding, subtracting, multiplying, and
dividing numbers
○ Understands instructions written in machine language and
included in its instruction set
○ Each brand of CPU has its own instruction set

● To carry out meaningful calculation, CPU must perform many
operations
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How Programs Work (cont’d)

● Program must be copied from secondary memory to RAM
each time CPU executes it
● CPU executes program in cycle:
○ Fetch: read the next instruction from memory into CPU
○ Decode: CPU decodes fetched instruction to determine which
operation to perform

○ Execute: perform the operation
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How Programs Work (cont’d)
Figure 1-16 The fetch-decode-execute cycle

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From Machine to Assembly Language
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Impractical for people to write in machine language
Assembly language: uses short words (mnemonics) for
instructions instead of binary numbers
○ Easier for programmers to work with
Assembler: translates assembly language to machine
language for execution by CPU

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From Machine to Assembly Language (cont
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compiled language)
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Code is translated by an interpreter one statement at a time
In a compiled language, the entire source code is translated then executed altogether

● An object-oriented language
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Data in Python are objects created from classes
A class is a type that defines objects of the same kind with common properties and
methods to manipulate them

● Installing Python: https://www
...
com/products/individual
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References
[1]

Tony Gaddis, 2018, Starting out with Python (4th Edition)
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