Download Memory & Storage: Lesson 6 Storing Characters and more Slides Computer science in PDF only on Docsity! Memory & Storage: Lesson 6 Storing Characters Starter A computers memory and storage only hold binary 1s and 0s • How might it be possible to store letters with only binary? Learning Outcomes: • Understand the use of binary codes to represent characters • Understand the term ‘character set’ • Explain the relationship between the number of bits per character in a character set, and the number of characters that can be represented using: • ASCII • Extended ASCII • Unicode Memory & Storage: Lesson 6 Storing Characters Memory & Storage: Lesson 6 Storing Characters Characters in binary • A keyboard needs to contain • 26 lowercase letters • 26 uppercase letters • 10 numbers • (around) 36 other characters • There are around 98 unique characters that are available on a keyboard • 6 bits give 64 different combinations – this isn’t enough • 7 bits give 128 different combinations which can represent 128 different characters Memory & Storage: Lesson 6 Storing Characters Character sets • A character set is a set of letters, symbols and digits that can be represented by a computer • There are two major character sets in use today • ASCII • Unicode Memory & Storage: Lesson 6 Storing Characters ASCII & Unicode….? • What is ASCII? • What is Unicode? • What is the difference between the two? Memory & Storage: Lesson 5 Storing Characters ASCII- Problems • Standard ASCII only uses the first 128 binary numbers available out of a possible 256. • Other languages such as German, French, Finnish, Irish, Icelandic etc take advantage of the another 128 values to include their own special characters. • This is called the extended ascii character set. Memory & Storage: Lesson 6 Storing Characters 7- and 8-bit ASCII • Numerous different codes for representing characters have been created, but ASCII is commonly used on PCs • Originally only seven bits were used, but now an eighth bit is used allowing for many more characters such as ©, ® etc. • How many different characters can be encoded using 7 bits, 8 bits or 16 bits? Memory & Storage: Lesson 6 Storing Characters Extended ASCII • A 7-bit character code (like ASCII) has 128 different characters that can be encoded • An 8-bit character code (like extended ASCII) has 256 different characters that can be encoded • A 16-bit character code has 65 536 different characters that can be encoded Memory & Storage: Lesson 6 Storing Characters Task 1: Storing Characters Complete Task 1 on the worksheet Navigation: � Student G-Suite � Computer Studies � GCSE Computer Science � Unit 1: Computer Systems � 1.2: Memory & Storage � Lesson 6: Storing Characters � Worksheet 1 Memory & Storage: Lesson 6 Storing Characters Programming with text & numbers • The ASCII code for ‘7’ is 011 0111 • The binary code for the digit 7 is 0000 0111 • When you write a program in Python, for example, you have to specify whether a variable is text or integer • You cannot do arithmetic with characters • If the character represents a number it must first be converted to an integer before any arithmetic can be carried out Memory & Storage: Lesson 6 Storing Characters Using different alphabets • To represent other characters for different languages, a new code allowing for many more characters is needed • Unicode was developed to use 16 bits 65 536 possible combinations • The 32 bit version gives 4 294 967 296 (over 4 billion) possible combinations Memory & Storage: Lesson 6 Storing Characters Smiling face with sunglasses Unicode: 1F60E Unicode • ‘good day’ requires 8 bytes to store •今日は requires 6 bytes to store (3 characters x 2 bytes) • Unicode is also used to store emoji • ‘e’ is Japanese for picture • ‘moji’ is Japanese for character or alphabet Memory & Storage: Lesson 6 Storing Characters Task 2: Programming Characters1. Complete Task 3 on the worksheet 2. Complete page 81 in the CGP: Practice Exam Questions book • Use Page 72 in the CGP: Revision Guide book to help you Navigation: � Student G-Suite � Computer Studies � GCSE Computer Science � Unit 1: Computer Systems � 1.2: Memory & Storage � Lesson 6: Storing Characters � Worksheet 1 Memory & Storage: Lesson 6 Storing Characters Ex am Q u e st io n :
