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[memory](notes/memory.md)
[unicode](notes/unicode.md)
[ASCII](notes/ASCII.md)
[characters](notes/characters.md)
[digital-data](notes/digital-data.md)

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---
title: "ASCII"
aliases:
tags:
- cosc204
---
# ASCII Character Code
![ascii code](https://i.imgur.com/NbBtm1v.png)
1. The computer uses ch as a integer index into a pre-existing table
2. the computer screen is made up of a thousand little dots called pixels. theyre in a rectangular grid like a table.a
- [ascii code example](https://i.imgur.com/9uvKRVo.png)
- There are several tables that describe what to draw
- fonts describe how to draw them
- ASCII (american standard code for information) describes what should be drawn for Roman (english like) alphabets
- e.g.,
- A 1000001 (65)
- B 1100001 (97)
- 9 0111001 (57)
- There are only a few letter numbers and punctuation marks. The remaining ASCII code are non-printing and have other meaning (line feed, for feed, tab etcc)
- ASCII characters are stored using 7-bits
- so there are 128 (2^7) possible characters
- stored as a byte with the 8th bit set to zero
- For sorting purposes characters are compared on their numeric value (called the *collating sequence*)
- 'A' is before 'Z' but 'a' is after 'Z'!

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---
title: "characters"
aliases:
tags:
- cosc204
---
# Characters
- A written symbol.
- In english are represented as a single byte, (other languages use 2 bytes or more)
- e.g., [different types of characters](https://i.imgur.com/DBLVhw8.png)
- characters are joined together to make human readable numbers and words
- `char ch`
- ch is a variable name (identifier)
- used to label a location in the computer's memory where a byte is stored
- when the code is compile, the name is assigned an address, in memory. The meaning of that data depends on how a human interprets it. it might be small integer, or a character, or a color etc.d
- each byte (or group of bytes) represents a number which maps to a character using a mapping like [Unicode](notes/characters.md#Unicode) or [ASCII](notes/characters.md#ASCII)
# ASCII
![ascii code|300](https://i.imgur.com/NbBtm1v.png)
A char is a 7-bit number (usually stored as a byte with the 8th bit set to zero) used as an index into a table of characters. The font describes how to draw these characters
- ASCII (american standard code for information) describes what should be drawn for Roman (english like) alphabets
- ASCII characters are stored using 7-bits
- so there are 128 (2^7) possible characters
- stored as a byte with the 8th bit set to zero
- For sorting purposes characters are compared on their numeric value (called the *collating sequence*)
- 'A' is before 'Z' but 'a' is after 'Z'!
# Unicode
![unicode|300](https://i.imgur.com/GEtVItW.png)
A 21-bit code with 144,697 characters from 159 scripts
- Other non roman languages
- greek, arabic, chinese, hebrew, japanese, thai etc.
- atrology symbols
- emoji etc
- Unicode
- developed by the Unicode Consortium
- coordinated with ISO/IEC 10646
- unicode maps from character numbers (code points) into glyphs (graphical representations)
- Some(many) are reserved

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> [!Definition]
> Combinatorial Logic Circuit is a circuit whose digital outputs are dependent only on its digital inputs
They can be described using logic expressions and therefore logic gates. We assume the outputs respond immediately^[1]
They can be described using logic expressions and therefore logic gates. We assume the outputs respond immediately
- current flows from + to -
- input to a unit (e.g., LED) is at the + end
@ -18,19 +18,18 @@ They can be defined:
- Using graphical symbols
# Adders
![1 Bit half adder](https://i.imgur.com/mjCVU4I.png)
![1 Bit full adder: (includes carry input)](https://i.imgur.com/yu6kS83.png)
![Ripple carry adder](https://i.imgur.com/HtEIZ5t.png)
![1 Bit half adder|300](https://i.imgur.com/mjCVU4I.png)
![1 Bit full adder: (includes carry input)|300](https://i.imgur.com/yu6kS83.png)
![Ripple carry adder|300](https://i.imgur.com/HtEIZ5t.png)
# Parity Generator
- 3 Bit parity Generator
- Adds an extra bit to the input data so that the number of ones in the output is always odd
- Used for error checking
- [truth table](https://i.imgur.com/KDUiJbN.png)
- [boolean equation](https://i.imgur.com/mwBpnlO.png)
- [circuit](https://i.imgur.com/tsgDISC.png)
Adds an extra bit to the input data so that the number of ones in the output is always odd. Used for error checking
![truth table|300](https://i.imgur.com/KDUiJbN.png)
![boolean equation|300](https://i.imgur.com/mwBpnlO.png)
![circuit|300](https://i.imgur.com/tsgDISC.png)
# Demux
# 7 Segment
- ![7 segment displlay](https://i.imgur.com/qtPmtwR.png)
![7 segment displlay|300](https://i.imgur.com/qtPmtwR.png)

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[page](https://cosc204.cspages.otago.ac.nz)
# Notes
- [ASCII](notes/ASCII.md)
- [unicode](notes/unicode.md)
- [characters](notes/characters.md)
- [digital-data](notes/digital-data.md)
- [memory](notes/memory.md)
- [boolean-equations](notes/boolean-equations.md)

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@ -39,15 +39,3 @@ Data is stored in [memory](notes/memory.md)
- [amount of bits for different devices](https://i.imgur.com/nHrz1zX.png)
# Characters
- A written symbol.
- In english are represented as a single byte, (other languages use 2 bytes or more)
- e.g., [different types of characters](https://i.imgur.com/DBLVhw8.png)
- characters are joined together to make human readable numbers and words
- `char ch`
- ch is a variable name (identifier)
- used to label a location in the computer's memory where a byte is stored
- when the code is compile, the name is assigned an address, in memory. The meaning of that data depends on how a human interprets it. it might be small integer, or a character, or a color etc.d
- each byte (or group of bytes) represents a number which maps to a character using a mapping like [unicode](notes/unicode.md) or [ASCII](notes/ASCII.md)

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---
title: "unicode"
aliases:
tags:
- cosc204
---
## Unicode
![unicode](https://i.imgur.com/GEtVItW.png)
- Other non roman languages
- greek, arabic, chinese, hebrew, japanese, thai etc.
- atrology symbols
- emoji etc
- Unicode
- developed by the Unicode Consortium
- coordinated with ISO/IEC 10646
- a 21-bit code with 144,697 characters from 159 scripts
- unicode maps from character numbers (code points) into glyphs (graphical representations)
- Some(many) are reserved