Searching and Replacing
In a small program like the one you just wrote, it's easy to find specific words or phrases. For example, if you want to find the keyword INPUT, just look at the screen and there it is. However, in large programs, finding text visually is tougher than chasing an angry bear up a tree. Luckily, QBasic includes search commands. These commands are, of course, found in the Search menu, shown in Figure 3.13.
Figure 3.13 QBasic's Search menu.
As you can see, the Search menu contains three entries: Find, Repeat Last Find, and Change. To find the next occurrence (starting at the text cursor's location) of any word or phrase, select the Find item of the Search menu. You'll see the dialog box in Figure 3.14.
When the Find dialog box appears, the word at the text cursor's location appears in the Find What edit box. If this is the word you want to find, just press Enter to start the search. If you want to look for a different word or phrase, type it into the Find What edit box and press Enter. If you don't want to search for a word or phrase, you might want to ask yourself why the heck you're staring at the Find dialog box.
Figure 3.14 The Find dialog box.
Try the Find command now by following these steps:
Press Ctrl+Home to place the blinking text cursor at the beginning of your program.
Select the Find item of the Search menu. The Find dialog box appears.
In the Find What edit box, type the word name and press Enter. QBasic finds and highlights the first occurrence of the word "name."
To find other occurrences of this word, select the Repeat Last Find entry of the Search menu or just press F3. Each time you select this command, QBasic finds another occurrence of the word "name."
Notice that QBasic doesn't care whether the word or phrase contains upper- or lowercase letters. Any match is okay. You can make the search case sensitive by checking the Match Upper/Lowercase option box. (Option boxes look like a pair of square brackets and are used to turn various options on or off.) When this option is selected, the search finds only words that match exactly, including the case of the letters.
To select an option box from the keyboard, follow these steps:
Press your keyboard's Tab key until the blinking text cursor is in the option's check box.
Tab to the option box and then press the spacebar to toggle (turn on or off) the option.
To toggle an option box with your mouse, place your mouse pointer over the option and click the left mouse button.
In addition to checking for case, you can also tell QBasic's search function to find only whole words. For example, suppose you're looking for the word "red" in your program. You select the find function, type in red, and press Enter. To your surprise, the first word the computer finds is "Fred." This is because the word "red" is part of "Fred." If you want to find only the complete word "red," you must check the Whole Word option box. Then the search function will ignore words that happen to contain the letters "red."
Now, suppose you've completed a program, and for some reason, you've decided you want to change all occurrences of the word "Name" to "FirstName". You could go through the entire program, line by line, and change each occurrence of the word yourself. However, in a large program, this task would take a lot of timeand make you madder than a hornet in a mason jar. Worse, you're almost certain to miss some occurrences of the word you want to change. A better way to tackle this problem is to use the Search menu's Change command. When you select this command, you see the dialog box in Figure 3.15.
Figure 3.15 The Change dialog box.
The Change dialog box looks much like the Find dialog box, except it has two edit boxes (boxes into which you can type text) instead of one and has different buttons at the bottom. To use the Change function, type the word you want to find into the Find What edit box. Then press Tab to move the text cursor to the Change To edit box and type the replacement text.
You then must select one of the buttons at the bottom of the dialog box. If you select the Find and Verify button, each time QBasic finds the target text, it'll ask whether you want to change it. If you select the Change All button, QBasic makes all the changes without further input from you. The Find and Verify button is often the best way to perform this type of global changeit ensures that only the words you want to change get changed.
To get a little experience with the Change function, use it to change all occurrences of "Name" in your program to "FirstName." If you need help, you can follow these numbered steps:
Select the Change entry of the Search menu. The Change dialog box appears.
Type the word Name into the Find What edit box.
Press the Tab key. The text cursor moves to the Change To edit box.
Type the word FirstName.
Press Tab. The text cursor moves to the Match Upper/Lowercase option box.
Press your spacebar to select the Match Upper/Lowercase option.
Press Tab until the text cursor is on the Change All button.
Press Enter to select the Change All button and change all occurrences of "Name" to "FirstName". A box appears containing the message "Change complete."
Press Enter to remove the message box.
After you complete this change, your program should still run properlyfor reasons you won't understand until later in this book. But, understand it or not, go ahead and run the program by pressing Shift+F5. Cool, huh? And the best news is that you're now ready to move on to Chapter 4, "Places Where Numbers Live," where you'll really start learning about programming. If you'd like to take a break, you can exit QBasic by selecting the Exit command of the File menu.
The Least You Need to Know
To run QBasic, change to the directory that contains its files and double-click the QBasic application file.
To load a program file, select the Open item of the File menu.
To save a program file to disk, use the Save or Save As item of the File menu.
To start a new program, select the New item of the File menu.
To print a program, select the Print entry of the File menu.
You can view offscreen portions of a program by using the edit window's scroll bars. From your keyboard, you can scroll a program with the Page Up, Page Down, and arrow keys.
QBasic changes all keywords to uppercase, regardless of how you type them. Keywords are the reserved words that make up a computer language.
QBasic can find syntax errors and warn you about them. However, it can't find all possible errors in your program.
To run a program, select the Start item of the Run menu or press F5 on your keyboard.
Using the QBasic editor, you can cut, copy, and paste text much like you would with a text editor. These editing commands are located in the Edit menu, but you can also select them by using shortcut keys.
The QBasic editor lets you find and replace words or phrases in your programs. The Find and Replace commands are in the Search menu.
To exit QBasic, select the Exit entry of the File menu.