Titlebook: Beginning BASIC with the ZX Spectrum; Judith Miller Textbook 1985Latest edition Macmillan Publishers Limited 1985 BASIC.computer science.p

HPA533

Introduction,The system is composed of three main parts as illustrated below:

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Interlocking

Correcting mistakes,In unit 1 you learned that a letter could be removed by pressing CAPS SHIFT and DELETE. Sometimes mistakes are not noticed immediately and you may have typed in a whole sentence before realising that a mistake has been made. In order to correct this mistake it is not necessary to delete the whole sentence.

議程

Making a program,The whole sentence plus the number and the keyword PRINT appears at the top of the screen. The computer is now making a . by storing the information for later use.

誹謗

More about numbering lines,Program lines are usually numbered in intervals of ten; for example, 10, 20, 30, 40 etc. The reason for this is that when a program is first made lines are often missed out by mistake. Having intervals of ten between lines enables a further nine lines to be inserted later if necessary. For example

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欄桿

,Testing your knowledge—questions on the Introduction and Units 1–5,Try to answer from memory as many questions as you can. Look up those you do not know in the appropriate unit — the questions are divided into sections. Check your answers at the back of the book.

indicate

Numeric or simple variables,A numeric or simple variable is a storage space in the computer’s memory which is given a name. The storage space stores only numbers, hence its name. The easiest way to imagine this is to think of a box that has a name and contains a number. The example below shows a box called ‘A’ storing the number 15.

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String variables, are the letters of the alphabet, the numbers 0 to 9, punctuation marks and special symbols as +, -, *.

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Using the computer as a calculator,For arithmetic you use four main operators: add, subtract, multiply and divide. BASIC language has the same operators although two are printed differently.