; Signed Integer Representation Model ; written by Crystal Barchet and Teresa Carrigan, 2004 globals [ from-number from-string number-of-digits start-x myDigits praise digits1 save-base base step ] breeds [ digit arrow ] arrow-own [ state ] patches-own [ name ] ; runs the program when it is first loaded to startup setup end ; initializes variables to setup locals [here-x current n] ca set praise ["Awesome!" "You got it!" "Right!" "Correct!" "Perfect!" "Bravo!" "Splendid!"] set digits1 [ "0" "1" ] set base 2 set save-base base set myDigits [] set n 0 set start-x 9 set here-x 7 set current 1 set n 0 repeat 2 [ set myDigits lput ( item n digits1 ) myDigits set n (n + 1) ] set n 1 ; initialize decimal number set from-number -32 + random 64 set from-string (word from-number "") if from-number >= 0 [ set from-string (word "+" from-string) ] ask patch-at 0 5 [ set plabel from-string ] ; create red arrow cct-arrow 1 [ hideturtle setxy start-x 0 set heading -90 set color red set shape "arrow" set size 2 set state 0 ] ; check for random format if random-format [ setup-random-format ] ; create explanation bar at bottom ask patches with [ pycor < -3 ] [set pcolor blue] ask patch-at 6 -4 [set plabel (word "Eight-bit " format " of a decimal integer,") set plabel-color white set name 1 ] ask patch-at 6 -5 [ set plabel-color white set plabel "starting with " + from-string + " decimal." set name 2 ] set step 1 end ; read the digits, storing it as a string to-report get-number [ howmany ] locals [ target n num] set target "" set n 7 repeat howmany [ if any? digit-at n 0 [ set num label-of random-one-of digit-at n 0 set target (word num target) ] set n (n - 2) ] set target remove " " target report target end ; adds a space in the number so it can be read easier to-report add-space [ target ] locals [ before after result k ] set k length target ifelse k > 4 [ set before substring target 0 4 set after substring target 4 k set result (word before " " after) ] [ set result target ] report result end ; this is for the bottom explanation to explain [ which what ] ask patches with [ name = which ] [ set plabel what ] end ; convert from decimal to unsigned binary to step1 explain 1 (word "Storing decimal integer " from-number ".") explain 2 "Step 1: Temporarily remove the sign." wait slow-motion ask patch-at -4 4 [ set name "sign" set plabel first from-string ] ask patch-at 4 4 [ set name "decimal" set plabel but-first from-string ] set step step + 1 wait slow-motion end to step2 locals [ num num-string unsigned dividend rem] explain 2 "Step 2: Convert to unsigned binary." set num-string but-first from-string set num read-from-string num-string set unsigned "" ; convert while [num > 0] [ set dividend int (num / 2) set rem (num mod 2) set unsigned (word rem unsigned) ask patch-at 4 3 [ set name "unsigned" set plabel unsigned ] set num dividend wait slow-motion ] explain 2 "Unsigned binary representation: " + (add-space unsigned) wait slow-motion setup-bits unsigned set step step + 1 end ; setup the bits to setup-bits [ unsigned ] locals [ here-x ] set number-of-digits length unsigned set here-x ( start-x - 2) repeat number-of-digits [ cct-digit 1 [ setxy here-x 0 set shape "circle" set color white set size 2 set label-color black set label (word (last unsigned) " ") ] ; end cct digits set unsigned but-last unsigned set here-x (here-x - 2) wait slow-motion ] end ; pad to 8 bits to step3 locals [ numdig ] explain 2 "Step 3: Pad to eight bits." set numdig 8 - number-of-digits ask arrow [ showturtle while [state < number-of-digits] [ if any? other-digit-here [ set state state + 1 set label state + " "] fd 1 wait slow-motion ] fd 1 wait slow-motion repeat numdig [ hatch 1 [ set breed digit set shape "circle" set color white set size 2 set label-color black set label "0 " ] ; end cct digits set state state + 1 set label state + " " fd 1 wait slow-motion fd 1 wait slow-motion ] ] set step step + 1 end ; if positive, then finished to step4 locals [ mySign ] explain 2 "Step 4: Check the sign." wait slow-motion * 3 ask patches with [ name = "sign" ] [ set mySign plabel ] ifelse mySign = "+" [ explain 2 "Positive, so we are finished." explain 1 (word from-number " decimal = " (add-space get-number 8) " " format " format.") set step 10 ] [ explain 2 "Negative, so we are not finished yet." ] set step (step + 1) wait slow-motion ask arrow [ hideturtle set label "" ] end ; handle signed magnitude case to step5 locals [ ] if format = "signed magnitude" [ explain 1 "Signed magnitude format and negative number," explain 2 "so just make the left-most bit 1." wait slow-motion * 2 ask min-one-of digit [ xcor ] [ set label "1 " set color yellow ] wait slow-motion explain 1 (word from-number " decimal = " (add-space get-number 8) ) explain 2 (word "using binary signed magnitude format.") set step 10 ] set step (step + 1) ask arrow [ hideturtle ] end ; find one's complement (invert all the bits) to step6 explain 1 (word format " and negative number") explain 2 "Invert each bit: 1 becomes 0 and 0 becomes 1." ask arrow [ showturtle setxy start-x 0 set state 0 repeat 18 [ fd 1 wait slow-motion if any? other-digit-here [ flip set state state + 1 ] ] ] explain 2 "Now in one's complement form." if format = "one's complement" [ set step 10 explain 1 (word from-number " decimal = " (add-space get-number 8) ) explain 2 (word "using one's complement format.") ] wait slow-motion * 2 set step step + 1 ask arrow [ hideturtle ] end ; add one to inverted number to step7 explain 2 "Add 1 to the inverted number." ask arrow [ showturtle setxy start-x 0 wait slow-motion fd 2 increment ] set step (step + 1) end ; the final answer is displayed to step8 explain 1 (word from-number " decimal = " (add-space get-number 8) ) explain 2 (word "using two's complement format.") set step 10 ask arrow [ hideturtle ] end ; add one to the bit pattern (arrow specific procedure) to increment wait slow-motion ifelse any? other-digit-here [ ask other-digit-here [ ifelse first label = "0" [ set label "1 " ask arrow [go-back] ] [ set label "0 " ask arrow [fd 2 increment] ] ; end ifelse ] ; end ask other-digit-here ] ; end then part of ifelse any? [ ask arrow [go-back] ] ; end ifelse any? end ; return red arrow to starting position to go-back rt 90 fd 5 wait slow-motion rt 90 set xcor start-x wait slow-motion rt 90 fd 5 wait slow-motion rt 90 set state "done" end ; cleans up the user input to-report clean-input [guess] locals [ pos k upper lowerList] set guess remove " " guess set guess remove "," guess report guess end ; creates a random quiz quesiton and praise if it is right and says its wrong if it is to ask-question locals [ guess save-slow target] set guess user-input (word "What is the eight bit " format " format of " from-number "?") set guess (word " " guess " " ) set guess clean-input guess set save-slow slow-motion set slow-motion 0 while [ step < 10 ] [ go ] set slow-motion save-slow without-interruption [ set target get-number 8] ifelse guess = target [ user-message random-one-of praise ] [ user-message "I'm sorry, but the correct answer is " + add-space target + "."] end ; sets up a random quiz to setup-random-format set format random-one-of [ "signed magnitude" "one's complement" "two's complement" ] end ; calls the quiz when the button is pressed to quiz locals [ save-slow ] set save-slow slow-motion set slow-motion 0 if random-format [ setup-random-format ] without-interruption [setup ] wait .5 ask-question set slow-motion save-slow end ; flips the digits (called by the invert procedure) to flip if any? other-digit-here [ ask other-digit-here [ set color yellow ifelse first label = "0" [ set label "1 " ] [ set label "0 " ] ] ] end ; do whatever step comes next, then wait until user wants to continue to one-step locals [ which ] if step < 10 [ set which (word "step" step) run which ] end ; this is the go button, that when pressed, goes through remainder of the simulation to go ifelse step < 10 [ one-step wait slow-motion ] [ stop ] end to show-again locals [here-x current n] set start-x 9 set here-x 7 set current 1 set n 1 ask turtles [ die ] ask patches [ set plabel "" ] ask patch-at 0 5 [ set plabel from-string ] ; create red arrow cct-arrow 1 [ hideturtle setxy start-x 0 set heading -90 set color red set shape "arrow" set size 2 set state 0 ] explain 1 (word "Eight-bit " format " of a decimal integer,") explain 2 "starting with " + from-string + " decimal." set step 1 end ; *** NetLogo Model Copyright Notice *** ; ; Copyright 2004 by Crystal Barchet and Teresa W. Carrigan. All rights reserved. ; ; Permission to use, modify or redistribute this model is hereby granted, ; provided that both of the following requirements are followed: ; a) this copyright notice is included. ; b) this model will not be redistributed for profit without permission ; from Teresa W. Carrigan. ; Contact Teresa W. Carrigan for appropriate licenses for redistribution ; for profit. ; ; To refer to this model in academic publications, please use: ; Barchet, C. and Carrigan, T. (2004). Signed Integer Representation Model. ; Blackburn College, Carlinville, IL. ; ; In other publications, please use: ; Copyright 2004 by Crystal Barchet and Teresa W. Carrigan. All rights reserved. ; ; *** End of NetLogo Model Copyright Notice *** @#$#@#$#@ GRAPHICS-WINDOW 13 10 548 316 10 5 25.0 1 18 1 1 1 CC-WINDOW 29 431 566 601 Command Center BUTTON 13 318 76 351 NIL setup NIL 1 T OBSERVER T SLIDER 143 318 315 351 slow-motion slow-motion 0 1 0.5 0.1 1 NIL BUTTON 13 351 76 384 step one-step NIL 1 T OBSERVER T BUTTON 78 319 141 352 NIL go T 1 T OBSERVER T BUTTON 78 352 141 385 quiz quiz NIL 1 T OBSERVER T CHOICE 327 319 546 364 format format "signed magnitude" "one's complement" "two's complement" 1 SWITCH 327 364 547 397 random-format random-format 0 1 -1000 BUTTON 143 353 316 386 NIL show-again NIL 1 T OBSERVER T @#$#@#$#@ WHAT IS IT? ----------- This model demonstrates the three formats for storing a signed decimal integer as an pattern of eight bits: signed magnitude, one's complement, and two's complement. HOW IT WORKS ------------ First, the sign is separated from the decimal digits. The decimal digits are then converted to unsigned binary, and padded to eight bits. If the sign is positive, then this is the answer, no matter which format is being used. When using signed magnitude, a negative number simply changes the left-most bit from a zero to a one. When using one's complement, a negative number simply inverts each bit. That is, each one becomes a zero, and each zero becomes a one. When using two's complement, first the one's complement is determined, and then we add one to get the answer. HOW TO USE IT ------------- The setup button generates a random signed decimal integer. The step button demonstrates the next step, and then stops so you can take notes. This is useful when you are first learning the method. The go button does every remaining step, at a speed determined by the slow-motion slider. This is useful when you do not need to take notes between each step. The show-again button starts the exact problem from the beginning. You may then click either the step button or the go button to see the same demonstration. The slow-motion slider is an easy way to adjust the speed of the display. Set it to zero if you want to show the final result as quickly as possible. 0.5 is a good setting for most purposes. If the random-format switch is off, then the format demonstrated is the one selected by the format choice box. If the switch is on, then a random format will be chosen. The format choice box allows you to select which format (signed magnitude, one's complement, two's complement) is demonstrated. The random-format switch must be off for your choice to be used. The quiz button will generate a random signed decimal integer and ask the user to convert it to either signed magnitude, one's complement, or two's complement. The format used is determined by the format choice box or the random-format switch. THINGS TO NOTICE ---------------- The answer will always have eight bits. Padding is done before inverting or adding one. If the decimal number is positive, then all three formats give the same bit pattern, and the left-most bit of the answer will be zero. If the decimal number is negative, then the three formats will give different bit patterns, but in each case the left-most bit of the answer will be one. THINGS TO TRY ------------- Set slow-motion to 0.5, select random format, click setup, and then click go. Set the format to a type you wish to drill, and set random-format off. Click setup. Work each step by hand, and then click the step button to check your answer. EXTENDING THE MODEL ------------------- Allow the user to input the starting decimal integer. Calculate and display all three formats for the same decimal integer. Allow the user to specify either eight-bit or sixteen-bit format. Allow a larger range for the generated decimal integer, and check for overflow. NETLOGO FEATURES ---------------- word is used to concatenate inputs together and reports the result as a string. one-step uses the NetLogo run command combined with a global integer variable step to run the next step, without needing nested ifelse blocks. without-interruption runs all the commands in the block without allowing other agents to "interrupt". That is, other agents are put "on hold" and do not execute any commands until the commands in the block are finished. RELATED MODELS -------------- Binary Counter, Successive Division CREDITS AND REFERENCES ---------------------- This model was written by Crystal Barchet and Teresa W. Carrigan, 2004. Permission to use, modify or redistribute this model is hereby granted, provided that both of the following requirements are followed: a) this copyright notice is included. b) this model will not be redistributed for profit without permission from Teresa W. Carrigan. Contact Teresa W. Carrigan for appropriate licenses for redistribution for profit. To refer to this model in academic publications, please use: Barchet C. and Carrigan, T. (2004). Signed Integer Representation Model. Blackburn College, Carlinville, IL. In other publications, please use: Copyright 2004 by Crystal Barchet and Teresa W. Carrigan. All rights reserved. FOR MORE INFORMATION -------------------- For more information on representation of negative integers, see one of the following textbooks: [1] Null, L. and Lobur, J. "Essentials of Computer Organization and Architecture", First Edition, Jones & Bartlett, pages 44-55. [2] Dale, N. and Lewis, J. "Computer Science Illuminated" Second Edition, Jones and Bartlett, page 59-63. @#$#@#$#@ default true 0 Polygon -7566196 true true 150 5 40 250 150 205 260 250 ant true 0 Polygon -7566196 true true 136 61 129 46 144 30 119 45 124 60 114 82 97 37 132 10 93 36 111 84 127 105 172 105 189 84 208 35 171 11 202 35 204 37 186 82 177 60 180 44 159 32 170 44 165 60 Polygon -7566196 true true 150 95 135 103 139 117 125 149 137 180 135 196 150 204 166 195 161 180 174 150 158 116 164 102 Polygon -7566196 true true 149 186 128 197 114 232 134 270 149 282 166 270 185 232 171 195 149 186 149 186 Polygon -7566196 true true 225 66 230 107 159 122 161 127 234 111 236 106 Polygon -7566196 true true 78 58 99 116 139 123 137 128 95 119 Polygon -7566196 true true 48 103 90 147 129 147 130 151 86 151 Polygon -7566196 true true 65 224 92 171 134 160 135 164 95 175 Polygon -7566196 true true 235 222 210 170 163 162 161 166 208 174 Polygon -7566196 true true 249 107 211 147 168 147 168 150 213 150 arrow true 0 Polygon -7566196 true true 150 0 0 150 105 150 105 293 195 293 195 150 300 150 bee true 0 Polygon -256 true false 152 149 77 163 67 195 67 211 74 234 85 252 100 264 116 276 134 286 151 300 167 285 182 278 206 260 220 242 226 218 226 195 222 166 Polygon -16777216 true false 150 149 128 151 114 151 98 145 80 122 80 103 81 83 95 67 117 58 141 54 151 53 177 55 195 66 207 82 211 94 211 116 204 139 189 149 171 152 Polygon -7566196 true true 151 54 119 59 96 60 81 50 78 39 87 25 103 18 115 23 121 13 150 1 180 14 189 23 197 17 210 19 222 30 222 44 212 57 192 58 Polygon -16777216 true false 70 185 74 171 223 172 224 186 Polygon -16777216 true false 67 211 71 226 224 226 225 211 67 211 Polygon -16777216 true false 91 257 106 269 195 269 211 255 Line -1 false 144 100 70 87 Line -1 false 70 87 45 87 Line -1 false 45 86 26 97 Line -1 false 26 96 22 115 Line -1 false 22 115 25 130 Line -1 false 26 131 37 141 Line -1 false 37 141 55 144 Line -1 false 55 143 143 101 Line -1 false 141 100 227 138 Line 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146 211 151 216 154 157 154 Polygon -7566196 true true 150 74 146 91 139 99 143 114 141 123 137 126 131 129 132 139 142 136 126 142 119 147 148 147 boat3 false 0 Polygon -1 true false 63 162 90 207 223 207 290 162 Rectangle -6524078 true false 150 32 157 162 Polygon -16776961 true false 150 34 131 49 145 47 147 48 149 49 Polygon -7566196 true true 158 37 172 45 188 59 202 79 217 109 220 130 218 147 204 156 158 156 161 142 170 123 170 102 169 88 165 62 Polygon -7566196 true true 149 66 142 78 139 96 141 111 146 139 148 147 110 147 113 131 118 106 126 71 box true 0 Polygon -7566196 true true 45 255 255 255 255 45 45 45 butterfly1 true 0 Polygon -16777216 true false 151 76 138 91 138 284 150 296 162 286 162 91 Polygon -7566196 true true 164 106 184 79 205 61 236 48 259 53 279 86 287 119 289 158 278 177 256 182 164 181 Polygon -7566196 true true 136 110 119 82 110 71 85 61 59 48 36 56 17 88 6 115 2 147 15 178 134 178 Polygon -7566196 true true 46 181 28 227 50 255 77 273 112 283 135 274 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113 253 119 231 119 215 143 213 160 208 173 189 187 169 190 154 190 126 180 106 171 72 171 73 126 122 126 144 123 159 123 Polygon -6524078 true true 201 99 214 69 215 99 Polygon -6524078 true true 207 98 223 71 220 101 Polygon -6524078 true true 184 172 189 234 203 238 203 246 187 247 180 239 171 180 Polygon -6524078 true true 197 174 204 220 218 224 219 234 201 232 195 225 179 179 Polygon -6524078 true true 78 167 95 187 95 208 79 220 92 234 98 235 100 249 81 246 76 241 61 212 65 195 52 170 45 150 44 128 55 121 69 121 81 135 Polygon -6524078 true true 48 143 58 141 Polygon -6524078 true true 46 136 68 137 Polygon -6524078 true true 45 129 35 142 37 159 53 192 47 210 62 238 80 237 Line -16777216 false 74 237 59 213 Line -16777216 false 59 213 59 212 Line -16777216 false 58 211 67 192 Polygon -6524078 true true 38 138 66 149 Polygon -6524078 true true 46 128 33 120 21 118 11 123 3 138 5 160 13 178 9 192 0 199 20 196 25 179 24 161 25 148 45 140 Polygon -6524078 true true 67 122 96 126 63 144 @#$#@#$#@ NetLogo 2.0.1 @#$#@#$#@ @#$#@#$#@ @#$#@#$#@