Learn to Program with Small Basic

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Nested Loops The statements in the body of a For loop can be any Small Basic statement, including another For loop. Nesting is when you put one For loop inside another For loop (no birds are involved). Using nested loops allows you to create iterations in two or more dimensions. This technique is important, and you can use it to solve a wide range of programming problems. To understand the idea of nested For loops, you’ll examine a program that causes your computer to “jump” four times and “clap” three times after each jump. Because the program needs to count two actions (jumps and claps), it needs to use two loops, as shown in Listing 13-7. The counter for the outer loop, j, runs from 1 to 4. The counter for the inner loop, c, runs from 1 to 3. 1 ' NestedLoops.sb 2 For j = 1 To 4 ' The jump counter 3 TextWindow.Write("Jump " + j + ": ") 4 For c = 1 To 3 ' The clap counter 5 TextWindow.Write("Clap " + c + " ") 6 EndFor 7 TextWindow.WriteLine("") 8 EndFor Listing 13-7: Nesting For loops In the first iteration of the outer loop (where j = 1), the inner loop repeats three times (for the three values of c); each time, it writes the word Clap followed by a space, the current value of c, and another space (line 5). When you nest For loops like this, the inner loop goes through all its iterations for each iteration of the outer loop. So the first iteration of the outer loop makes the program display Jump 1: Clap 1 Clap 2 Clap 3. When the inner loop ends, the program outputs an empty line (line 7) to move the cursor to the beginning of the next line, and the second iteration of the outer loop starts with j = 2. The inner loop runs again for c = 1, 2, and 3. This causes the program to display Jump 2: Clap 1 Clap 2 Clap 3. This continues, so the program displays Jump 3: Clap 1 Clap 2 Clap 3 and then Jump 4: Clap 1 Clap 2 Clap 3. Then the program ends. Perhaps your computer wants to be a cheerleader! Figure 13-6 helps to explain how the program works. The outer circle represents each time the outer loop runs: for example, at the top of the outer circle, when j = 1 in the outer loop, the inner loop runs three times, where c = 1, c = 2, and c = 3. Follow the outer loop and think through each inner loop. Continue until you get all the way around the outer circle. Repeating For Loops 189
3 j = 1 c 1 1 2 3 j = 4 c 2 2 c j = 2 2 3 1 1 c 3 j = 3 Figure 13-6: How NestedLoops.sb works The output should look like this: Jump 1: Clap 1 Clap 2 Clap 3 Jump 2: Clap 1 Clap 2 Clap 3 Jump 3: Clap 1 Clap 2 Clap 3 Jump 4: Clap 1 Clap 2 Clap 3 Now let’s look at other problems where nested For loops come in handy! Tessellating for Fun In this example, an application covers the graphics window by stamping a small image over it. The complete program is shown in Listing 13-8. 1 ' Stamp.sb 2 GraphicsWindow.Title = "Stamp" 3 4 path = Program.Directory 5 img = ImageList.LoadImage(path + "\Trophy.ico") 6 7 width = ImageList.GetWidthOfImage(img) ' Width of image 8 height = ImageList.GetHeightOfImage(img) ' Height of image 9 10 GraphicsWindow.Width = 8 * width ' 8 columns 11 GraphicsWindow.Height = 3 * height ' 3 rows 12 13 For row = 0 To 2 ' 3 rows 14 For col = 0 To 7 ' 8 columns 15 GraphicsWindow.DrawImage(img, col * width, row * height) 16 EndFor 17 EndFor Listing 13-8: Stamping a pattern across the graphics window 190 Chapter 13
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Learn to Program with Small Basic A
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Learn to Program with Small Basic A
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Brief Contents Foreword by Vijaye R
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Exploring Other Features. .........
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7 Empowering Programs with math 83
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12 building Graphical User Interfac
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Storing Records. ..................
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Foreword Computer programming is ma
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Acknowledgments This book represent
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Introduction Have you ever wondered
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• In Chapter 11: Event-Driven Pro
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1 Introducing Small Basic Bill Gate
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BASIC language that would help kids
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Toolbar Help Area Editor Surface Fi
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Then click the New button to open a
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Helping Hands: IntelliSense and Syn
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Programming Challenges If you get s
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The Parts of a Program Let’s expl
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The method’s name and a brief des
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5 + 7 12 Here’s the output of thi
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For example, to make the TextWindow
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TRY IT OUT 2-3 Now you have a chanc
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Programming Errors Just because a p
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26 Chapter 2 4. Write a program tha
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In the system you use at school, po
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Drawing Shapes You can draw lots of
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Figure 3-6 shows what the output lo
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22 GraphicsWindow.BrushColor = "Lig
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DrawText() takes three arguments. T
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GraphicsWindow provides two methods
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6. Write a program that draws this
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4 Using Variables Have you ever wan
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Try changing the value in karenBear
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These two ways of updating the scor
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Figure 4-2: How a variable is added
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TRY IT OUT 4-3 Write a program that
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Two Kinds of Data Programs use all
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5 Drawing Shapes with Turtle Graphi
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Absolute Motion With absolute motio
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North 0 (360) 315 (-45) 45 (-315) W
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GraphicsWindow.PenColor = "Red" Gra
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The For loop runs Turtle.Move(60) a
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y 5). For the hexagon (the polygon
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Creating Polygon Art Using Nested L
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Endless Graphics In Listing 5-10 yo
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Write a program to have the turtle
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Talking to the Computer Until now,
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Figure 6-2: The text window waiting
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4 C = (5 / 9) * (F - 32) 5 C = Math
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9 noun = TextWindow.Read() 10 11 Te
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7 Empowering Programs with Math If
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Here’s a sample run of our progra
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Round() -4 -3.5 -3 0 3 3.5 4 Round(
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This code snippet shows you some ex
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Let’s walk through this program l
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Trigonometric Methods Trigonometric
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Programming Challenges If you get s
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Small Basic uses a few different wa
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You can test all sorts of condition
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Small Basic first finds the value o
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Your mom’s instructions assume th
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But wait, your mom just realized th
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This code asks the user to enter a
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9 Using Decisions to Make Games Som
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Condition 1 True Statement set 1 If
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This change to the program means th
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Door 1 Door 2 Door 3 Figure 9-6: Pe
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Listing 9-4 shows an example of usi
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Think of the Shapes object as a “
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Background image (Grid.png) Star.pn
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In Figure 9-8, you see that the gri
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This code asks the player to enter
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10 Solving Problems with Subroutine
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Gulliver later learned that 1 glum-
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TRY IT OUT 10-1 When Gulliver asked
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variables that belong to the main p
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4 TextWindow.WriteLine("Your turn.
Page 164 and 165: 1 step away). If the arrow hits the
Page 166 and 167: Then you set the graphics window’
Page 168 and 169: 24 Shapes.SetText(msgText, "") 25 T
Page 170 and 171: Step 8: Shoot Arrows with ShootArro
Page 172 and 173: Lines 3-7 animate the dragon’s fi
Page 174 and 175: 11 Event-Driven Programming So far,
Page 176 and 177: GraphicsWindow Events Let’s start
Page 178 and 179: 4 5 Sub OnKeyDown 6 GraphicsWindow.
Page 180 and 181: 13 Else 14 GraphicsWindow.DrawText(
Page 182 and 183: Useful Tips Before moving on, we’
Page 184 and 185: 21 GraphicsWindow.BrushColor = "Red
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Page 188: Programming Challenges If you get s
Page 191 and 192: Today, most programs use a graphica
Page 193 and 194: located at (100, 100). By default,
Page 195 and 196: 9 GraphicsWindow.MouseMove = OnMous
Page 197 and 198: Let’s look at the computations. Y
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Page 203 and 204: TRY IT OUT 12-4 Write a program to
Page 206 and 207: 13 Repeating For Loops Have you eve
Page 208 and 209: Each For loop starts with the keywo
Page 210 and 211: The program uses a variable named s
Page 212 and 213: TRY IT OUT 13-5 What does the follo
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Page 221 and 222: In this chapter, you’ll learn how
Page 223 and 224: Note Although it’s not required b
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Page 229 and 230: Step 4: Announce the Winner The las
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Page 234 and 235: One way to think of an array is as
Page 236 and 237: The string initializer lets you fil
Page 238 and 239: TextWindow.WriteLine("Enter 5 numbe
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Page 242 and 243: To create this program, we’ll use
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Page 246 and 247: The subroutine uses a For loop to c
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Page 253 and 254: Associative Arrays In the previous
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Page 257 and 258: Here’s the output from a sample r
Page 259 and 260: The ContainsIndex() method takes tw
Page 261 and 262: Figure 16-1 shows the user interfac
Page 263 and 264: 1 Sub OnButtonClicked 2 GraphicsWin
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17 Expanding to Higher-Dimension Ar
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1 ' Random2DArray.sb 2 For r = 1 To
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Animated Squares Let’s write a pr
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12 TextWindow.Write("Enter student
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(line 8). Line 9 displays Scott's M
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You start by initializing the sum v
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4 For col = 1 To 4 ' For each colum
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note If you run into any problems,
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First, you set all the elements of
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11 If ((rowP < 1) Or (rowP > 10) Or
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Open the file Okla.sb from this cha
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(both uppercase and lowercase), dig
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Taking Strings Apart: Substrings Ju
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two arguments: the source string th
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Here’s an output example: Who's y
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More on Code Points The Unicode cod
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Line 7 gets the Nth character of th
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Igpay Atinlay Let’s teach the com
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17 TextWindow.WriteLine("Good Job!"
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9 pos = Math.GetRandomNumber(len) '
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When you continue with the second a
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TRY IT OUT 18-10 Use the techniques
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19 Receiving File Input and Output
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and their meanings. File extensions
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program’s folder (right-click the
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in the file would run together in o
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Let’s experiment with the first p
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line number. As with the WriteLine(
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WARNING If the destination path poi
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6 For N = 1 To count ' Displays the
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wizard asks the user to perform. Th
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Figure 19-8 shows a sample run of t
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Where to Go from Here So you’ve m
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Index Numbers and Symbols 3DArrayDe
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squares, 31-32 star, 65-66 triangle
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integrated development environment
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parts of, 14-16 publishing, 5-6 run
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NewGame() subroutine, 255-256 OnBut
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ages 10 and up “Welcome to the ma
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Learn to Program with Small Basic

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