mid term for python

Program

A set of instructions a computer follows to perform a task (also called software).

Programmer

"A person who designs

Hardware

The physical devices that make up a computer.

CPU

Central processing unit: the part of the computer that actually runs programs.

Microprocessor

A CPU located on a small chip.

Main memory (RAM)

"Where a program and its data are stored while running. Fast

Volatile memory

"Temporary storage whose contents are erased when the computer is turned off (e.g.

Secondary storage

Holds data for long periods; programs are stored here and loaded into RAM when needed.

Types of secondary storage

"Disk drive (magnetic)

Input device

"Component that collects data from people or other devices (keyboard

Output device

"Component that formats and presents data produced by the computer (display

Application software

"Programs that make the computer useful for everyday tasks (word processing

System software

Programs that control and manage the basic operations of a computer.

Operating system (OS)

System software that controls the operations of the hardware components.

Utility program

System software that performs a specific task to enhance computer operation or safeguard data.

Software development tools

"Programs used to create

Bit

Smallest unit of data; an on/off switch holding 0 or 1.

Byte

8 bits; enough memory to store one letter or a small number.

Range of one byte

0 (00000000) to 255 (11111111).

ASCII

American Standard Code for Information Interchange; numeric codes for 128 characters.

Unicode

Newer character coding standard; compatible with ASCII and covers other languages.

Two's complement

Scheme computers use to encode negative numbers.

Floating-point notation

Scheme computers use to encode real numbers.

Digital

Describes any device that stores data as binary numbers.

Pixel

Digital images are made of these; each is stored as a binary number for its color.

Sample

Digital music is made of these sections; each is stored as a binary number.

Machine language

"Binary instructions the CPU understands

Fetch-decode-execute cycle

Fetch: read next instruction from memory. Decode: determine the operation. Execute: perform it.

Assembly language

"Low-level language using short mnemonics (e.g.

Assembler

Program that translates assembly language into machine language.

High-level language

Language that makes it easy to create powerful programs without knowing how the CPU works.

Key words

Predefined words with specific meaning used to write programs in a high-level language.

Operator

"Symbol that performs an operation on data (e.g.

Syntax

The set of rules to follow when writing a program.

Statement

An individual instruction in a high-level language.

Compiler

Translates a whole high-level program into a separate machine language program that can be run any time.

Interpreter

Translates and executes high-level instructions one at a time; no separate program. Python uses one.

Source code

The statements written by the programmer.

Syntax error

An error that prevents code from being translated.

Number system

"Defined by the allowed symbols (digits)

Binary

"Base 2; digits 0

Octal

Base 8; digits 0-7.

Decimal

Base 10; digits 0-9.

Hexadecimal

Base 16; digits 0-9 and A-F.

Hex digit values

"A=10

Positional value formula

Digit x Base^position (position counted from 0 on the right).

Convert 1011 (binary) to decimal

1x8 + 0x4 + 1x2 + 1x1 = 11.

Convert 725 (octal) to decimal

7x64 + 2x8 + 5x1 = 469.

Convert 2F (hex) to decimal

2x16 + 15x1 = 47.

Method: decimal to binary

Repeatedly divide by 2; read the remainders from bottom to top.

Method: decimal to octal

Repeatedly divide by 8; read the remainders from bottom to top.

Method: decimal to hex

Repeatedly divide by 16; read remainders (10-15 as A-F) from bottom to top.

Convert 13 (decimal) to binary

1101.

Convert 83 (decimal) to octal

123.

Convert 250 (decimal) to hex

FA.

Binary to octal

Group bits in 3s from the right; convert each group. 110101 = 65 (octal).

Binary to hex

Group bits in 4s from the right; convert each group. 11101101 = ED.

Octal to binary

Replace each octal digit with 3 bits. 57 (octal) = 101111.

Hex to binary

Replace each hex digit with 4 bits. A3 = 10100011.

Where Python uses each base

"Binary internally; hex for memory

Why 8 bits in a byte

"2^8 = 256 values (0-255)

Binary 01000001 as a character

"Decimal 65

Bit vs byte analogy

Bit = a light switch (on/off). Byte = a group of 8 switches working together.

Convert 1101 (binary) to decimal

8 + 4 + 0 + 1 = 13.

Convert 11010 (binary) to decimal

16 + 8 + 0 + 2 + 0 = 26.

Four types of operations

"Arithmetic

Arithmetic operators

"+ addition

Modulus operator (%)

Returns the remainder of a division. 7 % 2 = 1; used to test odd/even.

Comparison operators

"==

== vs =

== compares two values; = assigns a value.

Logical operators

"AND (both true)

Boolean data type

Stores True (1/ON) or False (0/OFF); used to control program flow.

Operator priority (highest to lowest)

"Parentheses

5 - 3 * 4 + 2

-5 (multiply first: 5 - 12 + 2).

4 + 2 * 3 * 2 - 4

12.

5 - 3 - 4 + 2 * 2

2.

not ((10 - 2*3) < 5)

False (4 < 5 is True; NOT flips it).

AND truth rule

True only when both inputs are True.

OR truth rule

False only when both inputs are False.

Bitwise AND on 110011 and 001100

000000.

Bitwise OR on 110011 and 001100

111111.

Bitwise NOT on 110011

001100 (every bit flipped).

Who created Python and when

Guido van Rossum; released in 1991.

What Python is used for

"Web development (server-side)

Why Python

"Cross-platform

Current major Python version

Python 3.

IDE

"Integrated Development Environment (e.g.

How Python marks the end of a command

A new line (no semicolon or parentheses needed).

How Python defines scope

"Indentation (whitespace)

Software development process

"Problem definition

Algorithm

A step-by-step solution to a problem.

Flowchart

A graphical representation of an algorithm.

Pseudocode

"Plain-English

Flowchart: oval

Start / End.

Flowchart: parallelogram

Input / Output.

Flowchart: rectangle

Process.

Flowchart: diamond

Decision.

Flowchart: arrows

Flow of control.

Simple interest formula

"I = (P x R x N) / 100; P = principal

print()

Built-in function that displays text or values on the screen.