Download presentation
Presentation is loading. Please wait.
Published byCordelia Powers Modified over 9 years ago
1
Computer Science I Storing data. Binary numbers. Classwork/homework: Catch up. Do analysis of image types.
2
Overview Representation of information. How is everything/anything represented 'in' the computer (in storage)? –ANSWER: everything is represented using 1s and 0s. What the 1s and 0s mean depends on what the information is, for example, the datatype whole number, number with fraction, true/false value, character string, other…
3
Storage Everything (data and programs) is stored in the circuitry of 'the computer'. The circuitry includes transistors that are switches: on or off states, 0 or 1. Each switch is called a bit. So….numbers are stored using the binary (base 2) system Symbols (characters, letters, etc.) are stored using agreed upon systems of encoding –ASCII: 8 bits per character –UNICODE: 16 bits per character
4
Why? Why not use circuits that can directly represent numbers using the decimal (base 10) system? Answer: Easier to make on/off switches than something with 10 states. Easier to build circuitry for calculations for the base 2 addition and base 2 times tables than the ones you remember…
5
What is stored? Numbers: binary number system Characters: ASCII or UNICODE encoding Machine instructions Composite datatypes, for example String of characters representing text –Will get to arrays Images More…
6
Recall base 10 Recall 1s column, 10s column, 100s column Recall borrowing (re-grouping) and carrying Do problem(s)
7
Base 2 Same principle –1s column, 2s column, 4s column, ???? Your age? My age? Addition –Subtraction? Multiplication?
8
Joke Explain joke on shirt
9
Bits A bit is a one or a zero (1 or 0). 3 bits can hold how many different patterns? 000, 001, 010, 011, 100, 101, 110, 111 4 bits can hold how many different patterns? What is the formula?
10
Byte A byte is 8 bits. See in specs for computers, memory, etc. KB, Kb, Gb, GB, other. So, how many patterns, what is the biggest number, held by a byte?
11
Another Joke
12
Base 16 Hexadecimal: used for quick way to describe bits, mostly commonly for color coding Symbols used are 0, 1, 2, …, 9, A, B, C, D, E, F You have seen color coding: RGB (red, green blue) in hexadecimal FF0000 is red 00FF00 is green ??
13
Numbers with fraction part Aka numbers with a decimal point How to represent? ANSWER: floating point numbers aka scientific notation –3.4521 * 10 2 is the same as 345.21 * 10 0 –Terminology: 3.4521 (or 345.21) is the mantissa or significand and the 2 (or 0) is the exponent. Computer format: use 2 or 16 in place of 10 Example using 32 bits: – 1 bit for the sign (0 for +, 1 for -) – 8 bits for the exponent –23 bits for the mantissa (width, i.e., 23, is the precision)
14
Characters ASCII coding The character A is represented by 01000001 The character a is represented by 01100001 The character 1 is represented by 00110001 The character 2 is represented by 00110010 …. Unicode is a 16 bit format big enough (hopefully) for all the world's languages
15
String of characters …such as a name or a label or a piece of text Fixed length: allocate 1 byte (8 bits) for each character –UNICODE 2 bytes Variable length: store string in two parts –One part holds length as a number and pointer (address) of the whole string –String itself
16
Boolean Named after George Boole True / False Theoretically: 1 bit, 0 for false, 1 for true but The addressability requirement means it could be 1 byte or even bigger String of Booleans can be combined. –A byte can represent the answer to 8 true/false questions.
17
Images There are several different ways to represent images. Consider this simple way: – For each pixel, have 3 bytes of information: the bytes representing the level of red, green and blue. – So, for an image 400 by 300 pixels, how many bytes required for storage?
18
Machine instructions: back up Processing code is translated, multi-stage process, to basic language of the computer. Very, very basic instructions: –LR Load a register (part of the Central Processing Unit (CPU) with contents at particular address –AR add values in register –JUMP to a new instruction –Etc. Contains machine instruction command and other information, such as storage addresses, in binary.
19
Classwork / Homework Catch up. Upload of work past due, but will get some credit. Examine images and compare different types in quality and size. Make posting on forum.
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.