simple input (original) (raw)

music

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summary

Most programming languages have a simple method for input that we can use until we learn more sophisitcated techniques.

simple input

Most programming languages have a simple method for input that we can use until we learn more sophisitcated techniques.

While we won’t go into details about input, we will discuss a few additional simple options that may be useful in your first few programs.

single input

In Pascal a program must be declared to have input in the program header.

The Readln statement fetches data from the person using the program and will convert typed characters into numbers if necessary.

The input can come from punched cards, keyboard, or even a file.

program SimpleProgram (input, output);
var Age: integer;
begin
write ('How old are you? ');
readln (Age);
write ('You are ')
write (Age)
writeln (' years old ')
end.

multiple inputs

It is possible to have more than one number (or other items) entered with a single Readln statement.

program SimpleProgram (input, output);
var Age, OtherNumber: integer;
begin
write ('How old are you? ');
readln (Age, OtherNumber);
write ('You are ')
write (Age)
writeln (' years old ')
write ('Your other number is ')
writeln (OtherNumber)
end.

type match

Pascal expects each input to be of the correct type. Incorrect types may crash the program.

program SimpleProgram (input, output);
var Age: intger;
OtherNumber: real;
begin
write ('How old are you? ');
readln (Age, OtherNumber);
write ('You are ')
write (Age)
writeln (' years old ')
write ('Your other number is ')
writeln (OtherNumber)
end.

Notice that the reserved word var is used only once and a semicolon separator is used between the declarations.

one character at a time

It is sometimes desirable to read in one character at a time.

In Pascal any extra information on a card (or typed entry) that isn’t specifically asked for in the Readln statement is discarded and ignored.

You may use the Pascal statement Read to get one character at a time.

program SimpleProgram (input, output);
var FirstCharacter, SecondCharacter, ThirdCharacter, LastCharacter: char;
begin
write ('What is your password? ');
read (FirstCharacter, SecondCharacter, ThirdCharacter, LastCharacter);
write ('Your secret password is ')
writeln (FirstCharacter, SecondCharacter, ThirdCharacter, LastCharacter)
end.

free music player coding example

Coding example: I am making heavily documented and explained open source code for a method to play music for free — almost any song, no subscription fees, no download costs, no advertisements, all completely legal. This is done by building a front-end to YouTube (which checks the copyright permissions for you).

View music player in action: www.musicinpublic.com/.

Create your own copy from the original source code/ (presented for learning programming).

Because I no longer have the computer and software to make PDFs, the book is available as an HTML file, which you can convert into a PDF.

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