Thông tin tài liệu
An Introduction to Computer Systems David Vernon Copyright © 2007 David Vernon (www.vernon.eu) A Computer • • • takes input processes it according to stored instructions produces results as output Copyright â 2007 David Vernon (www.vernon.eu) Key Concepts ã ã • Input: Data Instructions: Software, Programs Output: Information (numbers, words, sounds, images) Copyright © 2007 David Vernon (www.vernon.eu) Types of Computer Computer Special Purpose (embedded systems) Pre-programmed General Purpose (user-programmable) Can be adapted to many situations Watches Traffic Signals Personal Computers Workstations Engine Management Televisions Mainframes Supercomputers Telephones Navigation Devices Copyright â 2007 David Vernon (www.vernon.eu) Data vs Information ã A • A – your grade in the exam • 2, 4, 23, 30, 31, 36 • 2, 4, 23, 30, 31, 36 – Next week’s Lotto numbers Copyright © 2007 David Vernon (www.vernon.eu) Key Concepts • Codes – Data and information can be represented as electrical signals (e.g Morse code) – A code is a set of symbols (such as dots and dashes in Morse code) that represents another set of symbols, » » » » such as the letters of the alphabet, or integers or real numbers, or light in an image, for the tone of a violin Copyright â 2007 David Vernon (www.vernon.eu) Key Concepts ã ã A circuit is an inter-connected set of electronic components that perform a function Integrated Circuits (ICs) – Combinations of thousands of circuits built on tiny pieces of silicon called chips Copyright â 2007 David Vernon (www.vernon.eu) Key Concepts ã Binary signal (two state signal) – – – – Data with two states off & on low voltage & high voltage 0v & 5v Copyright © 2007 David Vernon (www.vernon.eu) Key Concepts • Bit – Single Binary Digit – Can have value or 1, and nothing else – A bit is the smallest possible unit of information in a computer Copyright â 2007 David Vernon (www.vernon.eu) Key Concepts ã Groups of bits can represent data or information – – – – – – – bit - alternatives bits - alternatives bits - alternatives bits - 16 alternatives n n bits - alternativies 8bits - = 256 alternatives a group of bits is called a byte Copyright © 2007 David Vernon (www.vernon.eu) Full Adder • • The circuit to add three binary digits (two operands and a carry bit) is called a Full Adder (FA) It can be implemented using two half adders A B Ci Ci+1 FA S Copyright © 2007 David Vernon (www.vernon.eu) Full Adder , Co A HA B S , ,, Co Co HA S Ci Copyright â 2007 David Vernon (www.vernon.eu) Full Adder ã Addition is carried out in two stages – add bits A and B to produce » partial sum S’ » and (the first) intermediate output carry Co’ – add partial sum S’ and input carry Ci from previous stage to produce » final sum » and (the second) intermediate output carry Co’’ – We then need to combine the intermediate carry bits (they don’t have to be added) Copyright © 2007 David Vernon (www.vernon.eu) Full Adder A B Ci S’ Co’ Co’’ Co S A ⊕ B A ⊕ B ⊕ Ci 0 0 1 1 0 1 0 1 1 1 Copyright © 2007 David Vernon (www.vernon.eu) Full Adder A B Ci S’ Co’ Co’’ Co S A ⊕ B A ⊕ B ⊕ Ci 0 0 1 1 0 1 0 1 1 1 0 1 1 0 0 0 0 1 Copyright © 2007 David Vernon (www.vernon.eu) Full Adder A B Ci S’ Co’ Co’’ Co S A ⊕ B A ⊕ B ⊕ Ci 0 0 1 1 0 1 0 1 1 1 0 1 1 0 0 0 0 1 0 1 0 1 0 Copyright © 2007 David Vernon (www.vernon.eu) Full Adder A B Ci S’ Co’ Co’’ Co S A ⊕ B A ⊕ B ⊕ Ci 0 0 1 1 0 1 0 1 1 1 0 1 1 0 0 0 0 1 0 1 0 0 1 1 1 0 Copyright © 2007 David Vernon (www.vernon.eu) Full Adder A B Ci S’ Co’ Co’’ Co S A ⊕ B A ⊕ B ⊕ Ci 0 0 1 1 0 1 0 1 1 1 0 1 1 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 1 0 Copyright © 2007 David Vernon (www.vernon.eu) Full Adder A B Ci S’ Co’ Co’’ Co S A ⊕ B A ⊕ B ⊕ Ci 0 0 1 1 0 1 0 1 1 1 0 1 1 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 1 0 Copyright © 2007 David Vernon (www.vernon.eu) 1 0 Full Adder • A few observations The truth table demonstrates why Co = Co’ + Co’’ • It’s clear also that S = A ⊕ B ⊕ Ci • • Also, we could obtain a simplified expression for Co from a Karnaugh Map Co = A.B + B.Ci + A.Ci Copyright © 2007 David Vernon (www.vernon.eu) 3-Variable Karnaugh Map A=1 00 01 11 10 C=1 B=1 Copyright © 2007 David Vernon (www.vernon.eu) 3-Variable Karnaugh Map A=1 C=1 00 01 11 10 0 1 1 B=1 Co = A.B + B.Ci + A.Ci Copyright © 2007 David Vernon (www.vernon.eu) Full Adder • So, instead of implementing a full adder as two half adders, we could implement it directly from the gating: S = A ⊕ B ⊕ Ci Co = A.B + B.Ci + A.Ci Copyright © 2007 David Vernon (www.vernon.eu) Full Adder • Irrespective of the implementation of a full adder, we can combine them to add multiple digit binary numbers Copyright © 2007 David Vernon (www.vernon.eu) 4-Bit Binary Adder S3 S2 S0 S1 Co Co Co Co Full Adder Full Adder Full Adder Half Adder Ci A3 B3 Ci A2 B2 Ci A1 B1 Copyright © 2007 David Vernon (www.vernon.eu) A0 B0 ... operation of the computer system Copyright © 2007 David Vernon (www .vernon. eu) Components of Computer Systems Copyright © 2007 David Vernon (www .vernon. eu) Components of Computer Systems • • • •... © 2007 David Vernon (www .vernon. eu) Line Printer Key Components • • • • Input Output Storage Processor Copyright © 2007 David Vernon (www .vernon. eu) Storage Systems STORAGE • Units of Storage... 2007 David Vernon (www .vernon. eu) INPUT Input Systems ã Mouse » Cursor manipulation device » Trackball Copyright © 2007 David Vernon (www .vernon. eu) Keyboard Mouse INPUT Input Systems Keyboard Touch
Ngày đăng: 02/04/2021, 09:45
Xem thêm:
