Binary Number Systems

Total Page:16

File Type:pdf, Size:1020Kb

Binary Number Systems ENGI1006 PYTHON Summer 2021 1 Number Systems 2 OTHER NUMBER SYSTEMS • The western scientific world relies on decimal, or base 10 • as did the Ancient Egyptians, Incans, Greeks, Romans • Mayans used vegisimal, or base 20 • The Babylonians used sexagesimal, or base 60 • http://mentalfloss.com/article/31879/12-mind-blowing- number-systems-other-languages 3 BINARY NUMBER SYSTEMS • All modern digital devices rely on a simple scheme, intimately tied to transistors: • 1 - On • 0 - Off 4 BINARY NUMBER SYSTEMS • We call this base 2 number a bit • 8 bits form a byte • Use Greek prefixes, but in base 2 • Kilobyte is ~1000 Bytes, but is actually 2^10 bytes (1024 bytes) • Sometimes different prefixes are used (kibi vs kilo) 5 CONVERTING TO BINARY • We start by formalizing our understanding of decimal, or “base 10” • The digits of a number are multipliers for the powers of our base 6 CONVERTING TO BINARY • Thus, we can express a base 10 number as powers of 10 • 10,436 = 1*104 + 0*103 + 4*102 + 3*101+ 6*100 • Thus, in any other base, a number is composed of digits between 0 and (base - 1), times powers of the base 7 CONVERTING TO BINARY • So in binary • 10110 = 1*24 + 0*23 + 1*22 + 1*21 + 0*20 = 22 in decimal • Or in octal (base 8) • 75 in octal = 7*81 + 5*80 = 61 in decimal 8 CONVERTING TO BINARY • These operations are second nature to us in decimal, which can often make them confusing in other bases 9 CONVERTING TO BINARY • Converting a decimal number to a different base is a little bit harder • Luckily, there is a straightforward process (or algorithm, a term we will define later) for doing so • Given a number in decimal, if we divide repeatedly by a given base with remainder, the remainders will correspond to the digits in that base 10 CONVERTING TO BINARY • 1234 = 1*103 + 2*102 + 3*101 + 4*100 • = (1*103 + 2*102 + 3*101) + 4 • if we divide by 10 with remainder, its clear the remainder is 4, and the result is • 1*102 + 2*101 + 3*100 = (1*102 + 2*101) + 3 11 CONVERTING TO BINARY • Repeating the process until the quotient is 0 will yield me back the digits • Since my choice of base 10 was arbitrary, I can do the same for any other base, I.e. • 1234 = 1*103 + 2*102 + 3*101 + 4*100 • = Bn*2n + … + B0*20 • A slightly more mathematical explanation is here 12 CONVERTING TO BINARY • Let’s look at a few examples on the board 13 OTHER NUMBER SYSTEMS • Occasionally, we will use octal (base 8) • We sometimes use a hexadecimal (base 16) system to represent whole bytes with less data • i.e., (10101111)2 can be represented as (AF)16 14 15 BINARY ADDITION • Just like any other number system, we can do arithmetic • In fact, since all data on your computer is stored in binary, this is how the computer does calculations 16 BINARY ADDITION • Addition in decimal is second nature to us, but lets think about how we do it • To add up 2 numbers, we simple add them digit by digit • Then for any given pair of digits, since the numbers must be between 0 and 9, the resulting addition is between 0 and 18 • If the result requires more than one digit (e.g. 10 to 18), we carry over the second digit to our next calculation 17 BINARY ADDITION • In binary, it works the same. Each pair of numbers is between 0 and 1, so the resulting addition is between 0 and 3 in decimal, or between 0 and 11 in binary (0, 1, 10, or 11) • If the result requires more than one digit, we carry over the second digit to our next calculation 18 BINARY ADDITION • Let’s look at a few examples on the board 19 DEALING WITH NEGATIVES • In the decimal system, we use a “-“ to delineate negative numbers • In the binary system, there are two primary options • using a single bit for sign • two’s complement, a special scheme 20 DEALING WITH NEGATIVES • Signed binary numbers utilize the first bit as just an indicator of the sign of the remaining bits • So in 4 bits, the number 6 is represented as 0110 or equivalently +110, while the number -6 is represented as 1110 or equivalently -110 21 DEALING WITH NEGATIVES • There are 2 big drawbacks to this scheme • First, we always have both +0 and -0, which is annoying if we ever want to make comparisons to 0 • For example, if we want to check if a number is =0, we must check if = +0 or = -0 22 DEALING WITH NEGATIVES • Additionally, to do operations like (5 - 7), we need to do the same complicated subtraction algorithms we learned as children, but with the added complexity of binary • Wouldn’t it be great if we could just use the simple addition we already know? 23 COMPLEMENT • We can utilize the method of complements to make subtraction easy • You might have learned this for decimal as a way to do quick mental subtraction • This method makes binary subtraction a lot easier, with the caveat that we must only operate on a fixed number of bits (e.g. we limit ourselves to 4 bits) 24 ONE’S COMPLEMENT • One’s complement is not widely used, but its worth it as a stepping stone to two’s complement • For positive numbers, we represent them the same as signed binary • For negative numbers, we represent them by taking the positive number and flipping all the bits • Thus, all positive numbers start with 0 and all negative numbers start with 1 25 ONE’S COMPLEMENT • The number 6 is represented as 0110 • The number -6 is represented as 1001 • Given an unknown number 1010, we know its negative because it starts with 1, so we flip the bits • The result is 0101 = 5, so 1010 = -5 26 ONE’S COMPLEMENT 011 3 3 010 2 2 001 1 1 000 0 0 111 -3 -0 110 -2 -1 101 -1 -2 100 -0 -3 27 ONE’S COMPLEMENT • To do subtraction then becomes easy • To do 4-7, we just do 4+(-7) • 4 is 0100, 7 is 1000 • 0100 + 1000 = 1100 = -(0011) = -3 28 ONE’S COMPLEMENT • We’ve solved our subtraction problem, but unfortunately • +0 = 0000 = 1111 = -0 • so we still have 2 zeros 29 ONE’S COMPLEMENT • To fix this, we should shift our negative numbers down by one • So in 4 bits, instead of our numbers going between 0 and 7 and -0 and -7, they’ll go between 0 and 7 and -1 and -8, with no duplicates • This scheme is called Two’s Complement 30 TWO’S COMPLEMENT • Similarly to one’s complement and signed binary, all positive numbers start with 0 and all negative numbers start with 1 • The only difference with one’s complement is that after flipping the bits, we add 00…..01 to our number • Its counterintuitive to add 1 when we want to subtract one from our negative numbers, but remember that one’s and two’s complement make negative numbers symmetric 31 TWO’S COMPLEMENT • The number 6 is represented as 0110 • The number -6 is represented as 1010 • For -6, we start with 6 (0110), flip the bits (1001), and then add 0001 (1010) • Given an unknown number 1010, we know its negative because it starts with 1, so we flip the bits and add 1 • 1010, then flip the bits (0101), then add 0001 (0110), so 1010 = -6 32 TWO’S COMPLEMENT 011 3 3 010 2 2 001 1 1 000 0 0 111 -3 -1 110 -2 -2 101 -1 -3 100 -0 -4 33 TWO’S COMPLEMENT • Subtraction remains easy • To do 4-7, we just do 4+(-7) • 4 is 0100 • To figure out -7 we start with 7 (0111), flip the bits (1000) and add 0001 ( 1001) • 0100 + 1001 = 1101 • We know 1101 is negative because it starts with a 1, so we flip the bits (0010) and add 0001 (0011) • so our result is -3 34 TWO’S COMPLEMENT • Let’s go through a few conversion and addition examples on the board 35.
Recommended publications
  • Maths Week 2021
    Maths Week 2021 Survivor Series/Kia Mōrehurehu Monday Level 5 Questions What to do for students 1 You can work with one or two others. Teams can be different each day. 2 Do the tasks and write any working you did, along with your answers, in the spaces provided (or where your teacher says). 3 Your teacher will tell you how you can get the answers to the questions and/or have your work checked. 4 When you have finished each day, your teacher will give you a word or words from a proverb. 5 At the end of the week, put the words together in the right order and you will be able to find the complete proverb! Your teacher may ask you to explain what the proverb means. 6 Good luck. Task 1 – numbers in te reo Māori The following chart gives numbers in te reo Māori. Look at the chart carefully and note the patterns in the way the names are built up from 10 onwards. Work out what each of the numbers in the following calculations is, do each calculation, and write the answer in te reo Māori. Question Answer (a) whitu + toru (b) whā x wa (c) tekau mā waru – rua (d) ono tekau ma whā + rua tekau ma iwa (e) toru tekau ma rua + waru x tekau mā ono Task 2 - Roman numerals The picture shows the Roman Emperor, Julius Caesar, who was born in the year 100 BC. (a) How many years ago was 100 BC? You may have seen places where numbers have been written in Roman numerals.
    [Show full text]
  • Bits, Data Types, and Operations
    Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Agenda 1. Data Types 2. Unsigned & Signed Integers 3. Arithmetic Operations Chapter 2 4. Logical Operations 5. Shifting Bits, Data Types, 6. Hexadecimal & Octal Notation and Operations 7. Other Data Types COMPSCI210 S1C 2009 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Data Types Computer is a binary digital system. How do we represent data in a computer? Digital system: Binary (base two) system: At the lowest level, a computer is an electronic machine. • finite number of symbols • has two states: 0 and 1 • works by controlling the flow of electrons Easy to recognize two conditions: 1. presence of a voltage – we’ll call this state “1” 2. absence of a voltage – we’ll call this state “0” Basic unit of information is the binary digit, or bit. Values with more than two states require multiple bits. • A collection of two bits has four possible states: Could base state on value of voltage, 00, 01, 10, 11 but control and detection circuits more complex. • A collection of three bits has eight possible states: • compare turning on a light switch to 000, 001, 010, 011, 100, 101, 110, 111 measuring or regulating voltage • A collection of n bits has 2n possible states. COMPSCI210 S1C 2009 3 COMPSCI210 S1C 2009 4 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
    [Show full text]
  • Abstract of Counting Systems of Papua New Guinea and Oceania
    Abstract of http://www.uog.ac.pg/glec/thesis/ch1web/ABSTRACT.htm Abstract of Counting Systems of Papua New Guinea and Oceania by Glendon A. Lean In modern technological societies we take the existence of numbers and the act of counting for granted: they occur in most everyday activities. They are regarded as being sufficiently important to warrant their occupying a substantial part of the primary school curriculum. Most of us, however, would find it difficult to answer with any authority several basic questions about number and counting. For example, how and when did numbers arise in human cultures: are they relatively recent inventions or are they an ancient feature of language? Is counting an important part of all cultures or only of some? Do all cultures count in essentially the same ways? In English, for example, we use what is known as a base 10 counting system and this is true of other European languages. Indeed our view of counting and number tends to be very much a Eurocentric one and yet the large majority the languages spoken in the world - about 4500 - are not European in nature but are the languages of the indigenous peoples of the Pacific, Africa, and the Americas. If we take these into account we obtain a quite different picture of counting systems from that of the Eurocentric view. This study, which attempts to answer these questions, is the culmination of more than twenty years on the counting systems of the indigenous and largely unwritten languages of the Pacific region and it involved extensive fieldwork as well as the consultation of published and rare unpublished sources.
    [Show full text]
  • 2 1 2 = 30 60 and 1
    Math 153 Spring 2010 R. Schultz SOLUTIONS TO EXERCISES FROM math153exercises01.pdf As usual, \Burton" refers to the Seventh Edition of the course text by Burton (the page numbers for the Sixth Edition may be off slightly). Problems from Burton, p. 28 3. The fraction 1=6 is equal to 10=60 and therefore the sexagesimal expression is 0;10. To find the expansion for 1=9 we need to solve 1=9 = x=60. By elementary algebra this means 2 9x = 60 or x = 6 3 . Thus 6 2 1 6 40 1 x = + = + 60 3 · 60 60 60 · 60 which yields the sexagsimal expression 0; 10; 40 for 1/9. Finding the expression for 1/5 just amounts to writing this as 12/60, so the form here is 0;12. 1 1 30 To find 1=24 we again write 1=24 = x=60 and solve for x to get x = 2 2 . Now 2 = 60 and therefore we can proceed as in the second example to conclude that the sexagesimal form for 1/24 is 0;2,30. 1 One proceeds similarly for 1/40, solving 1=40 = x=60 to get x = 1 2 . Much as in the preceding discussion this yields the form 0;1,30. Finally, the same method leads to the equation 5=12 = x=60, which implies that 5/12 has the sexagesimal form 0;25. 4. We shall only rewrite these in standard base 10 fractional notation. The answers are in the back of Burton. (a) The sexagesimal number 1,23,45 is equal to 1 3600 + 23 60 + 45.
    [Show full text]
  • 1. Understanding Decimal, Binary, Octal and Hexadecimal Numbers
    Objectives: 1. Understanding decimal, binary, octal and hexadecimal numbers. 2. Counting in decimal, binary, octal and hexadecimal systems. 3. Convert a number from one number system to another system. 4. Advantage of octal and hexadecimal systems. 1. Understanding decimal, binary, octal and hexadecimal numbers Decimal number systems: Decimal numbers are made of decimal digits: (0,1,2,3,4,5,6,7,8,9 --------10-base system) The decimal system is a "positional-value system" in which the value of a digit depends on its position. Examples: 453→4 hundreds, 5 tens and 3 units. 4 is the most weight called "most significant digit" MSD. 3 carries the last weight called "least significant digit" LSD. number of items that a decimal number represent: 9261= (9× )+(2× )+(6× )+(1× ) The decimal fractions: 3267.317= (3× )+(2× )+(6× )+(7× )+ (3× ) + (6× ) + (1× ) Decimal point used to separate the integer and fractional part of the number. Formal notation→ . Decimal position values of powers of (10). Positional values "weights" 2 7 7 8 3 . 2 3 4 5 MSD LSD Binary numbers: . Base-2 system (0 or 1). We can represent any quantity that can be represented in decimal or other number systems using binary numbers. Binary number is also positional–value system (power of 2). Example: 1101.011 1 1 0 1 . 0 1 1 MSD LSD Notes: . To find the equivalent of binary numbers in decimal system , we simply take the sum of products of each digit value (0,1)and its positional value: Example: = (1× ) + (0× ) + (1× ) + (1× )+ (1× )+ (0× ) +(1× ) = 8 + 0 + 2 + 1 + + 0 + = In general, any number (decimal, binary, octal and hexadecimal) is simply the sum of products of each digit value and its positional value.
    [Show full text]
  • Bit, Byte, and Binary
    Bit, Byte, and Binary Number of Number of values 2 raised to the power Number of bytes Unit bits 1 2 1 Bit 0 / 1 2 4 2 3 8 3 4 16 4 Nibble Hexadecimal unit 5 32 5 6 64 6 7 128 7 8 256 8 1 Byte One character 9 512 9 10 1024 10 16 65,536 16 2 Number of bytes 2 raised to the power Unit 1 Byte One character 1024 10 KiloByte (Kb) Small text 1,048,576 20 MegaByte (Mb) A book 1,073,741,824 30 GigaByte (Gb) An large encyclopedia 1,099,511,627,776 40 TeraByte bit: Short for binary digit, the smallest unit of information on a machine. John Tukey, a leading statistician and adviser to five presidents first used the term in 1946. A single bit can hold only one of two values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units. For example, a byte is composed of 8 consecutive bits. Computers are sometimes classified by the number of bits they can process at one time or by the number of bits they use to represent addresses. These two values are not always the same, which leads to confusion. For example, classifying a computer as a 32-bit machine might mean that its data registers are 32 bits wide or that it uses 32 bits to identify each address in memory. Whereas larger registers make a computer faster, using more bits for addresses enables a machine to support larger programs.
    [Show full text]
  • Number Systems and Number Representation Aarti Gupta
    Number Systems and Number Representation Aarti Gupta 1 For Your Amusement Question: Why do computer programmers confuse Christmas and Halloween? Answer: Because 25 Dec = 31 Oct -- http://www.electronicsweekly.com 2 Goals of this Lecture Help you learn (or refresh your memory) about: • The binary, hexadecimal, and octal number systems • Finite representation of unsigned integers • Finite representation of signed integers • Finite representation of rational numbers (if time) Why? • A power programmer must know number systems and data representation to fully understand C’s primitive data types Primitive values and the operations on them 3 Agenda Number Systems Finite representation of unsigned integers Finite representation of signed integers Finite representation of rational numbers (if time) 4 The Decimal Number System Name • “decem” (Latin) => ten Characteristics • Ten symbols • 0 1 2 3 4 5 6 7 8 9 • Positional • 2945 ≠ 2495 • 2945 = (2*103) + (9*102) + (4*101) + (5*100) (Most) people use the decimal number system Why? 5 The Binary Number System Name • “binarius” (Latin) => two Characteristics • Two symbols • 0 1 • Positional • 1010B ≠ 1100B Most (digital) computers use the binary number system Why? Terminology • Bit: a binary digit • Byte: (typically) 8 bits 6 Decimal-Binary Equivalence Decimal Binary Decimal Binary 0 0 16 10000 1 1 17 10001 2 10 18 10010 3 11 19 10011 4 100 20 10100 5 101 21 10101 6 110 22 10110 7 111 23 10111 8 1000 24 11000 9 1001 25 11001 10 1010 26 11010 11 1011 27 11011 12 1100 28 11100 13 1101 29 11101 14 1110 30 11110 15 1111 31 11111 ..
    [Show full text]
  • 1 Evolution and Base Conversion
    Indian Institute of Information Technology Design and Manufacturing, Kancheepuram logo.png Chennai { 600 127, India Instructor An Autonomous Institute under MHRD, Govt of India N.Sadagopan http://www.iiitdm.ac.in Computational Engineering Objectives: • To learn to work with machines (computers, ATMs, Coffee vending machines). • To understand how machines think and work. • To design instructions which machines can understand so that a computational task can be performed. • To learn a language which machines can understand so that human-machine interaction can take place. • To understand the limitations of machines: what can be computed and what can not be computed using machines. Outcome: To program a computer for a given computational task involving one or more of arithmetic, algebraic, logical, relational operations. 1 Evolution and Base Conversion Why Machines ? We shall now discuss the importance of automation; human-centric approach (manual) versus machines. Although machines are designed by humans, for many practical reasons, machines are superior to humans as far as problem solving is concerned. We shall highlight below commonly observed features that make machines powerful. • Reliable, accurate and efficient. • Can do parallel tasks if trained. • Efficient while peforming computations with large numbers. If designed correctly, then there is no scope for error. • Good at micro-level analysis with precision. • Consistent It is important to highlight that not all problems can be solved using machines (computers). For example, (i) whether a person is happy (ii) whether a person is lying (not speaking the truth) (iii) reciting the natural number set (iv) singing a song in a particular raga. Computer: A computational machine In this lecture, we shall discuss a computational machine called computer.
    [Show full text]
  • Binary Numbers
    Binary Numbers X. Zhang Fordham Univ. 1 Numeral System ! A way for expressing numbers, using symbols in a consistent manner. ! ! "11" can be interpreted differently:! ! in the binary symbol: three! ! in the decimal symbol: eleven! ! “LXXX” represents 80 in Roman numeral system! ! For every number, there is a unique representation (or at least a standard one) in the numeral system 2 Modern numeral system ! Positional base 10 numeral systems ! ◦ Mostly originated from India (Hindu-Arabic numeral system or Arabic numerals)! ! Positional number system (or place value system)! ◦ use same symbol for different orders of magnitude! ! For example, “1262” in base 10! ◦ the “2” in the rightmost is in “one’s place” representing “2 ones”! ◦ The “2” in the third position from right is in “hundred’s place”, representing “2 hundreds”! ◦ “one thousand 2 hundred and sixty two”! ◦ 1*103+2*102+6*101+2*100 3 Modern numeral system (2) ! In base 10 numeral system! ! there is 10 symbols: 0, 1, 2, 3, …, 9! ! Arithmetic operations for positional system is simple! ! Algorithm for multi-digit addition, subtraction, multiplication and division! ! This is a Chinese Abacus (there are many other types of Abacus in other civilizations) dated back to 200 BC 4 Other Positional Numeral System ! Base: number of digits (symbols) used in the system.! ◦ Base 2 (i.e., binary): only use 0 and 1! ◦ Base 8 (octal): only use 0,1,…7! ◦ Base 16 (hexadecimal): use 0,1,…9, A,B,C,D,E,F! ! Like in decimal system, ! ◦ Rightmost digit: represents its value times the base to the zeroth power!
    [Show full text]
  • Application of Number System in Maths
    Application Of Number System In Maths Zollie is mystifying: she verbifies ethnically and unhusk her zoom. Elton congees pointlessly as Griswoldthigmotropic always Brooks scowls precipitates enharmonically her kinswoman and associated debussed his stout-heartedly.coatracks. Associable and communal Traces of the anthropomorphic origin of counting systems can is found show many languages. Thank you hesitate your rating. Accordingly there can be no fit in determining the place. Below provided a technique for harm with division problems with deed or more digits in the assert on the abacus. Attempts have been made people adopt better systems, fill it determined, they reresent zero and when that are rocked to verify right side represent one. Now customize the name see a clipboard to repeal your clips. Study the mortgage number systems in the joy given here. Indians abandoned the rest of rational numbers on the principal amount of the acuity at shanghai: number of natural numbers are related role of each week. The development of getting ten symbols and their use until a positional system comes to us primarily from India. Learn via the applications of algebra in women life. The one quantity is having constant multiple of more reciprocal demand the other. In this blog, a college entrance exam that includes many formal math abilities. We recommend just writing work somewhere this whole class can gauge them. Kagan curriculum for the base value numbers are not control for simplicity, telling us understand only eight is a tool for people attending class of number system in maths. When casting a hexagram, a the system how a spit to represent numbers.
    [Show full text]
  • Conversion from Decimal There Is a Simple Method That Allows Conversions from the Decimal to a Target Number System
    APPENDICES A Number Systems This appendix introduces background material on various number systems and representations. We start the appendix with a discussion of various number systems, including the binary and hexadecimal systems. When we use multiple number systems, we need to convert numbers from system to another We present details on how such number conversions are done. We then give details on integer representations. We cover both unsigned and signed integer representations. We close the appendix with a discussion of the floating-point numbers. Positional Number Systems The number systems that we discuss here are based on positional number systems. The decimal number system that we are already familiar with is an example of a positional number system. In contrast, the Roman numeral system is not a positional number system. Every positional number system has a radix or base, and an alphabet. The base is a positive number. For example, the decimal system is a base-10 system. The number of symbols in the alphabet is equal to the base of the number system. The alphabet of the decimal system is 0 through 9, a total of 10 symbols or digits. In this appendix, we discuss four number systems that are relevant in the context of computer systems and programming. These are the decimal (base-10), binary (base-2), octal (base-8), and hexadecimal (base-16) number systems. Our intention in including the familiar decimal system is to use it to explain some fundamental concepts of positional number systems. Computers internally use the binary system. The remaining two number systems—octal and hexadecimal—are used mainly for convenience to write a binary number even though they are number systems on their own.
    [Show full text]
  • Sec 1.1.1 Binary Number System Computer Science 2210 with Majid Tahir
    Computer Science 2210 Sec 1.1.1 Binary Number System with Majid Tahir Bits and binary: Computers use binary - the digits 0 and 1 - to store data. A binary digit, or bit, is the smallest unit of data in computing. It is represented by a 0 or a 1. Binary numbers are made up of binary digits (bits), e.g. the binary number 1001. The circuits in a computer's processor are made up of billions of transistors. A transistor is a tiny switch that is activated by the electronic signals it receives. The digits 1 and 0 used in binary reflect the on and off states of a transistor. Computer programs are sets of instructions. Each instruction is translated into machine code - simple binary codes that activate the CPU. Programmers write computer code and this is converted by a translator into binary instructions that the processor can execute. All software, music, documents, and any other information that is processed by a computer, is also stored using binary. Encoding: Everything on a computer is represented as streams of binary numbers. Audio, images and characters all look like binary numbers in machine code. These numbers are encoded in different data formats to give them meaning, e.g. the 8-bit pattern 01000001 could be the number 65, the character 'A', or a color in an image. Encoding formats have been standardized to help compatibility across different platforms. For example: audio is encoded as audio file formats, e.g. mp3, WAV, AAC video is encoded as video file formats, e.g. MPEG4, H264 text is encoded in character sets, e.g.
    [Show full text]