Apple employees, including Randy Wigginton , adapted Microsoft's interpreter for the Apple II and added several features. The first version of Applesoft was released in on cassette tape and lacked proper support for high-resolution graphics. It is this latter version, which has some syntax differences and support for the Apple II high-resolution graphics modes, that is usually synonymous with the term "Applesoft. When Steve Wozniak wrote Integer BASIC for the Apple II , he did not implement support for floating point math because he was primarily interested in writing games, a task for which integers alone were sufficient.
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The rest of the manual is a careful and exact description of every statement in the language and how each statement works. To help save you the frustration and annoyance that some manuals can cause, this manual points out places where programming errors can cause you difficulty. Special symbols call your attention to these points. You will find that, after a few moments getting used to it, it will speed your understanding of exactly what is legal and illegal in the language. You will not be left with any nagging doubts about the interpretation of a sentence, as can happen with pure English descriptions.
Advanced programmers will find this manual especially helpful. Beginning programmers are reminded that they will soon no longer be beginners, and will appreciate the extra effort APPLE has made to provide an unusually complete manual. To be sure, a thicker manual looks more formidable, but when you need the Information, you will be glad that we took the time and space to put it in.
XII There are two terms you'll need to know when reading this manual. The word "syntax" refers to the structure of a computer command, the order and correct form of the command's various parts. The word "parse" refers to the way in which the computer attempts to interpret what you type, picking out the various parts of the computer commands in order to execute them. Many primary concepts are introduced, using examples that you can type into the computer.
It will save you time and effort in understanding how the commands must be structured. You don't need to use this notation yourself, but it will help you answer many questions not specifically discussed in the text. The syntactic abbreviations and definitions in the first part of Chapter 2 are presented in a logical order for those who want to see how we've built up our system of symbols and definitions. You may prefer to ignore these symbols and definitions until you encounter one in the text.
At that time, you can refer to the alphabetized glossary of syntactic terms given in Appendix N. If you're interested in finding out about a specific command, the alphabetized index on the inside of the back cover will tell you where to look. Additional reference material not covered in the chapters can be found in the appendices. This symbol indicates an unusual feature to which you should be alert.
The use of the comma with the PRINT command divides the character line into 3 columns or "tab fields. There is another type of command called a "deferred-execution" command. Every deferred-execution command begins with a "line number". A line number is an integer from to A sequence of deferred-execution commands is called a "program. However, it makes no difference in what order you type deferred-execution statements. This is accomplished by typing the line number of the line you wish to delete, followed only by a press of the RETL'RN key.
There is no way to get it back. An increment of 10 between line numbers is generally sufficient. If you want to erase the complete program currently stored in memory, type NEW If you are finished running one program, and are about to begin a new one, be sure to type NEW first.
This should be done to prevent a mixture of the old and new programs. Numbers are stored internally to over nine digits of accuracy.
When a number is printed, only nine digits are shown. Every number may also have an exponent a power-of-ten scaling factor. Using addition or subtraction, you may sometlraes be able to generate numbers as large as 1.
In addition to these limitations, true integer values must be in the range from to When a number is printed, the following rules are used to determine the exact format: 1 If the number is negative, a minus sign - is printed. Scientific notation is used to print real precision numbers, and is formatted as follows: SX. The leading S is the sign of the number, nothing for a positive number and a minus sign - for a negative number. One non-zero digit is printed before the decimal point.
This Is followed by the decimal point and then the other eight digits of the mantissa. An E is then printed for Exponent , followed by the sign S of the exponent; then the two digits TT of the exponent itself. Leading zeroes are never printed; I. Also, trailing zeroes are never printed. If there Is only one digit to print after all trailing zeroes are suppressed, no decimal point is printed. Two digits of the exponent are always printed; that is, zeroes are not suppressed in the exponent field.
The value of any number expressed in the form of scientific notation as described above is the number to the left of the E times 10 raised to the power of the number to the right of the E.
However, only the first 10 digits are usually significant, and the tenth digit is rounded off. If the square is not yellow, your TV set is not tuned properly: adjust the tint and color controls to achieve a clear lemon yellow.
When PRlNTing the answers to problems, it is often desirable to include text along with the answers, in order to explain the meaning of the numbers. If we use a semicolon ; instead of a comma, the next value will be printed immediately following the previous value. Try it. Then execution continues with the next statement in the program, which is line 20 in the above example.
When the formula after the PRINT statement is evaluated, the value 10 is substituted for the variable R each time R appears in the formula. Therefore, the formula becomes 3. If you haven't already guessed, the program above calculates the area of a circle with the radius R. If we wanted to calculate the area of various circles, wg could keep re-running the program for each successive circle.
This could go on Indefinitely, but we decided to stop after calculating the area for three circles. This caused a "break" in the program's execution, allowing us to stop.
Using control C, any program can be stopped after executing the current Instruction. Try It for yourself. A variable name must begin witii an alphabetic character and may be followed by any alphanumeric character.
An alphanumeric character is any letter from A through Z, or any digit from through 9. In a variable name, any alphanumeric characters after the first two are ignored unless they contain a "reserved word. You cannot use these words as variable names or as part of any variable name. BASIC "remembers" the values that have been assigned to variables using this type of statement.
The values of variables are thrown away and the space in memory used to store them is released when one of four things occurs: 1 A new line is typed into the program or an old line is deleted. Here is another important fact: until you assign them some other value, all numeric variables are automatically assigned the value zero.
REM is short for remark. This statement is used to insert comments or notes into a program. This serves mainly as an aid to the programmer, and serves no useful function as far as the operation of the program in solving a particular problem. THEN Let's write a program to check whether a typed number is zero or not. With the statements we've discussed so Ear, this can not be done.
What we need is a statement that provides a conditional branch to another statement. The IF THEN statement does just that. Type any value you wish. The computer will then come to the IF statement. Following this command, the computer will skip to line Suppose a 1 is typed for B.
Program execution then skips to the statement following the next line number, printing A IS LARGER, and finally line 40 sends the computer back to line 10 to begin again.
Finally, line 70 send the computer back to the beginning again. Try running the last two programs several times. Then try writing your own program using the IF. THEN statement. Note the use of REM statements for clarity. The colon : is used to separate multiple instructions on one numbered program line. After you type the program below, LIST it and make sure that you have typed it correctly. Then RUN it. It also clears the A0 by 40 plotting area to black, sets the text output to a window of 4 lines of 40 characters each at the bottom of the screen, and sets the next color to be plotted to black.
HOME is used to clear the text area and set tlie cursor to the top left corner of the currently defined text window. In color GRaphics mode, this would be the beginning of text line 20, since text lines through 19 are now being used for the color graphics plotting area.
Applesoft BASIC Quick Reference